Glossary Flashcards
Absolute Pitch (AP)
Also called perfect pitch, it is the rare (approximately 1:10,000) ability to accurately produce and identify a pitch chroma immediately, without the aid of an external or internal (e.g., long-term memory for an anchor pitch) reference.
Acoustic Reflex
An automatic nervous system response that contracts the ossicles of the middle ear, pulling them closer together to dampen vibrations at the oval window. The acoustic reflex minimizes hearing damage from high-intensity sound pressure waves with durations longer than 200ms or so.
Action Potential
The electrical signal conducted along neural axons or muscle fibers by which information is conveyed from one place to another in the nervous system.
Active Process
In cognitive psychology, referring to a process that requires attention, conscious participation, or a source of additional energy; cf. passive.
Adaptation
In psychometrics, adaptation refers to the tendency for sensory organs to adjust to the intensity or quality of stimulation. Good examples are the eyes adapting to the level of light or nose adapting to the smell in a room.
ADSR
This initialism refers to Attack, Decay, Sustain, and Release — the four primary characteristics of a sound wave’s envelope.
Afferent
An axon that conducts action potentials from the periphery toward the central nervous system.
Amplitude
The intensity of a pressure wave or electrical signal, it is measured on the y-axis graphically.
Amplitude Modulation
Amplitude modulation can refer to a technique whereby one frequency (the carrier, or fc) is combined with a much lower frequency, the modulator (fm). Amplitude modulation is used in radio broadcasting. Amplitude modulation also refers to the result of two waves with slightly different frequency (f1 and f2) combining in and out of phase, and the resultant wave rising and falling in amplitude at a frequency equal to f2 – f1. If the difference frequency is between 2 and 15 Hz, it is perceived as beating. If it is between 15 and 200 Hz, it is perceived as roughness.
Amplitude-Normalize
Loss or impairment of the ability to produce or comprehend music or musical tones. Amusia appears mainly as a deficit in pitch processing but musical memory and melody recognition are also impaired.
Analytic Listening
In music, the tendency to focus on the local details of individual pitches, chords, harmonies, timbres, and other components of a musical signal.
Anterior
Towards the front of an animal or structure. Anterior may be used as a synonym for rostral or ventral.
Aperiodic
A waveform or event that does not repeat in form or is irregular. Aperiodic sounds are not perceived as having pitch.
Apex
The top or highest part of something. In auditory science it is used to refer to the distal or far end of the basilar membrane where low frequency waves reach their peak.
Aphasia
The loss of ability to speak or understand speech caused by brain damage. Aphasia is different from aphonia which is the loss of speech due to mechanical damage in the throat.
Arcuate Fasciculus
A connective axonal tract in the temporal lobes linking regions important for speech (Broca’s area) and language (Wernicke’s area) processing.
Auditory Brainstem Response (ABR)
An electrical potential in the auditory nerve bundle from cochlear nuclei to the thalamus that is evoked by an auditory stimulus. The ABR occurs within milliseconds of stimulus onset and is measured by sensitive electrodes placed on the scalp, forehead, and/or below the ear.
Auditory Feedback
In signal processing, the return of a portion of the output signal to the input of a processing stage. Feedback is useful in controlling the output intensity of a gain stage. In behavioral tasks, auditory feedback refers to the capacity to hear one’s own performance.
Auditory Filter (also Cochlear Filter)
One of an array of bandpass filters that exist behaviorally in the peripheral auditory system, starting with the basilar membrane. Filter bandwidths are determined empirically by masking experiments.
Auditory Nerve Bundle
The auditory (or cochlear) nerve bundle is one half of the vestibulocochlear nerve, labeled cranial nerve VIII. It refers to the nerves that carry sensory information from the cochlea to the primary auditory cortex.
Auditory Pathway
Neural structures serving the auditory system from the inner ears to the primary auditory cortex in the temporal lobes.
Auditory Scene Analysis
The process by which the human auditory system organizes the sensation of sound waves into perceptually meaningful elements.
Autocorrelation
The correlation of a signal with a delayed copy of itself as a function of delay, or the similarity between observations as a function of the time lag between them. Autocorrelation is a mathematical tool for finding repeating patterns, such as the presence of a periodic
signal obscured by noise, or identifying the missing fundamental frequency in a signal implied by its harmonic frequencies.
A-Weighting
The most commonly used in a family of curves relating to the measurement of sound pressure level. It takes into account the fact that human listeners are less sensitive to low- frequency sounds. It is commonly used to measure low intensity sounds. Measurements using A-weightings are expressed in dB(A). B- and C-weightings are flatter and used to measure moderate and high-intensity sources.
Axon
The long protrusion of a nerve cell that carries the action potential from cell body to the synapse or a target.
Azimuth
The position of a sound source along an imaginary plane dividing the body into left and right sides. Directly in front is 0 degrees, at the left ear is 90 degrees, behind the head is 180 degrees, and at the right ear is -90 or 270 degrees azimuth.
Bandwidth
A range of frequencies within two points on a frequency spectrum. Bandwidth is typically measured from the 3-dB-down points where the maximum output has fallen by three decibels.
Base
The bottom or lowest part of something. In auditory science it refers to the proximal or close end of the basilar membrane, at the oval window where high frequency waves reach their peak.
Basilar Membrane
The flexible membrane that bifurcates the bony cochlear shell and serves as a foundation for the rows of inner and outer hair cells just above it. Its up and down motion is caused by the push-and-pull action of the oval window in response to sound pressure variations originating in the ear canal.
Beating (Beats)
A periodic amplitude variation due to the combination of two sounds, electrical signals, or other vibrations having similar but not identical frequencies. It is an unpleasant sensation in the range of 2 to 15 Hz that contributes to sensory dissonance.
Binaural
Referring to a sound delivered to both ears.
Binaural Diplacusis
The observation that an identical tone presented to both ears will sometimes generate slightly different pitches in the listener.
Bottom-Up
Information processing that begins with the sensation of a stimulus and leads to the perception of an object. It is sometimes referred to as “data-driven processing” because it takes as a starting point the physical properties of a stimulus; cf. top-down processing.
Brainstem
The portion of the central nervous system that lies between the spinal cord and the cerebrum; it comprises the medulla, pons, and midbrain.
Central Sulcus
A major sulcus that forms the boundary between the frontal and parietal lobes. The primary motor cortex is anterior to the central sulcus; the somatosensory cortex is posterior to the sulcus.
Cerebellum
Prominent hindbrain structure that routes much nervous system activity between the cerebrum and spinal cord, especially signals concerned with movement, posture, and balance.
Cerebrum
The largest region of the brain in humans and other animals, consisting of two cerebral hemispheres.
Characteristic Frequency (CF)
The frequency at which the threshold of a given single neuron is lowest, i.e., the frequency at which it is most sensitive. It can also refer to the frequency at which a given place on the basilar membrane is most sensitive.
Cochlea
The coiled structure within the inner ear where vibrations are transduced into mechanical (on the basilar membrane) and electrochemical (in the hair cell) activity that is interpreted as sound.
Cochlear Nucleus
A structural complex that is the first destination for nerve spikes arriving from the cochlea via the auditory nerve, and is the first auditory information processing stage. Left and right cochlear nuclei are located in the medulla of the brainstem.
Cognition (Cognitive Psychology)
Thinking and acquiring knowledge, and the study of the same.
Common Fate
The Gestalt principle of common fate describes the tendency to regard items or events that move together as belonging together.
Complex Tone (Complex Wave)
Any tone comprising more than one frequency component; the wave shape will not be purely sinusoidal. Harmonic complex tones have frequency components (called partials) related to each other by whole numbers (integers). Inharmonic complex tones have frequency components that are unrelated to each other by whole numbers. Virtually all naturally occurring tones are complex.
Condensation
In wave theory “condensation” refers to a region of higher, compressed molecular density and pressure.
Cone of Confusion
A cone-shaped set of location points radiating outwards from the ear from which a pure tone would produce identical phase and timing delays. Consequently, the source’s perceived location is ambiguous because it could be anywhere on the surface of the cone. Head movements resolve the ambiguity.
Confound
A variable not accounted for in the experimental design that is responsible for the observed phenomenon. For example, if the morning section of a class consistently gets lower test scores than the afternoon section of the same class, sleepiness may be a confounding variable.
Consonance
Combined notes that are in harmony with each other due to the relationship between their frequencies. Cognitive (also called musical or tonal) consonance refers to two tones in small-integer ratio relationships, such as the octave (1:2) and perfect 5th (2:3). Sensory consonance refers to complex tones that lack beating, roughness, or other qualities that may contribute to their being judged as unpleasant or dissonant. Sensory and cognitive consonance coincide for most, but not all, musical dyads and chords. Major 3rds in low octaves, for example, are sensory dissonant but cognitively consonant.
Contralateral
Relating to or denoting the opposite side of the body from a particular structure or event; cf. ipsilateral.
Coronal Plane
An imaginary plane dividing the brain into front and back halves. A coronal view shows a cutaway of the brain from either the face side or the back of the head.
Corpus Callosum
The large midline fiber bundle connecting the cortices of the two cerebral hemispheres. It is viewed from the sagittal plane.
Cortex (pl. Cortices)
The surface layer of the brain, approximately 2-4 millimeters thick, composed of gray matter. In humans the cortex has multiple folds to permit greater surface area within the skull.
Cosine Wave
Signal waveform with a shape identical to that of a sine wave, except each point on the cosine wave occurs exactly 1/4 cycle earlier than the corresponding point on the sine wave. Practically speaking, sine waves start at 0° phase (0 amplitude) and cosine waves start at 90° phase (maximum amplitude) at time zero.
Crest Factor
The ratio of peak value to rms value of a waveform. A higher value indicates a large peak to rms ratio. A square wave has no peaks, therefore it has a crest factor of 1. A sine wave has a crest factor of 1.414.
Critical Bandwidth (CB)
A measure of the effective bandwidth of the auditory filter, determined by masking experiments. It is often defined by mapping some aspect of perception as a function of the stimulus and trying to determine a point where perception drastically changes.
Critical Period
In developmental psychology and developmental biology, a critical period is a maturational stage in the lifespan of an organism during which the nervous system is especially sensitive to certain environmental stimuli. If the organism does not receive the appropriate stimulus during this “critical period” to learn a given skill or trait, it may be difficult, ultimately less successful, or even impossible to develop some functions later in life. Examples include language acquisition and absolute pitch perception.
Cytoarchitecture
The arrangement of cells in tissue or nerve cells in the brain.
d’
A statistical measure of a responder’s sensitivity to signal strength in the presence of
noise. It is computed using the hit and false alarm rates and converting them to z scores.
Decibel (dB)
A logarithmic unit that expresses the ratio of two values of a physical quantity, such as power or intensity. A decibel is a comparison of two things, not a thing itself. It is useful in auditory science because the human auditory system is capable of converting an extraordinarily large range of sound pressure levels into audible signals and thus must be measured and discussed on a logarithmic scale.
Decoding
In biological sciences, decoding is an information-processing function performed in the cerebrum to convert a neural signal or pattern of neural activity into intelligible language or recognizable objects.
Dendrite
The portion of a nerve cell that receives synaptic input from sensory organs or other nerve cells in the form of ions, voltage changes, or neurotransmitters to propagate action potentials down the axon. Dendrites are distinct from axons in that they are typically shorter and there are many more of them per cell.
Dendritic Spine
Small protrusions from a neuron’s dendrite that strengthens the axon/dendrite connection. New dendritic spines are formed at dendrites that receive a lot of input.
Dependent Variable (DV)
The variable that is measured; an experimental design presumes that the dependent variable changes in the presence of the independent variables. For example, presenting a click track at various tempos to see how well people can keep time to a beat. In this case the DV is the degree of accuracy.
Depolarize
In life sciences, the displacement of a cell’s cross-membrane potential toward a less negative value. If depolarization crosses a sensitivity threshold in a nerve cell it will initiate an action potential.
Detection
Awareness of a stimulus. Detection does not involve knowledge or decision-making; cf. discrimination.
Dichotic
The simultaneous delivery of different sounds to the right and left ear; cf. diotic. For persons with normal hearing, dichotic sounds are perceived as coming from a stereo source.
Diffraction
The process by which light or sound waves bend around objects in their path.
Diffusion Tensor Imaging (DTI)
A magnetic resonance imaging technique that shows the diffusion or travel of molecules (esp. water) through tissue structures. In brain science it is used to map connectivity tracts due to the fact that water travels at different rates through various kinds of fibers.
Diotic
The simultaneous delivery of identical sounds to the right and left ear; cf. dichotic. For persons with normal hearing, diotic sounds are perceived as coming from a single mono source.
Discrimination
The ability to judge that two stimuli are different from one another. In classical conditioning, discrimination is determined by different responses to stimuli when the responses lead to different outcomes. Discrimination can be learned provided that stimulus differences are greater than the just-noticeable difference.
Dissonance
The combination of notes that is inharmonious with each other due to the relationship between their frequencies. Cognitive (also called musical or tonal) dissonance refers to two tones in large-integer ratio relationships to each other, such as the tritone (32:45) and minor 7th (9:16). Sensory dissonance refers to a complex tone with frequency components that cause beating, roughness, or other qualities that may contribute to its being judged as unpleasant. Sensory and cognitive dissonance are not coincident in certain musical dyads such as major 3rds in low octaves (sensory dissonant, cognitively consonant).
Duration
In auditory science it is the period from the onset of an event to its offset.
Dyad
Two musical pitches played simultaneously, c.f. a chord (three or more pitches).
Echo Suppression
A phenomenon whereby two separate sounds arriving in quick succession will eventually be heard as fused unless or until something in the sound stream changes. Echo suppression is a higher-level computation that attempts to diminish echoes and allow the source to be heard more clearly.
Efferent
An axon that conducts information away from the central nervous system and towards a muscle or organ.
Electroencephalogram (EEG)
An electrophysiological monitoring method to record electrical activity of the brain. It is typically noninvasive, with surface electrodes placed along the scalp, forehead, and nape of neck, jawbone, and/or earlobe. EEG measures voltage fluctuations resulting from ionic current in brain and brainstem neurons. EEGs can be seen in sleeping or comatose patients, provided that there is blood flow to the brain.
Electromotility
A property of outer hair cells that allows them to rapidly change their length in response to electrical stimulation. Direct current pulses can elongate or shorten the cell; continuous stimulation results in mechanical oscillations at the acoustic frequency. Outer hair cells positioned at the characteristic frequency of the input signal thus add force to it; for outer hair cells that are off-resonance, out of phase mechanical activity diminishes vibrations in the unstimulated regions of the inner ear.
Elevation
The height of a sound source in relation to an imaginary plane at the level of the ears or bottom of the nose. It is expressed in degrees with 0 degrees being nose level, 90 degrees being directly above the head and -90 degrees being below the body.
Emergence
Emergence is a phenomenon whereby complex properties occur in systems built of units without those properties, that is, where a property exists only of the whole, and not of the parts that make it up.
Encoding
In biological sciences, encoding is the conversion of mechanical or electrochemical activity into action potentials that may be distributed across a neural network in a specific pattern. Patterns of neural activity may be decoded in higher brain regions to become intelligible language or recognizable objects.
Endogenous
Having an internal cause or origin; cf. exogenous.
Endolymph
The potassium-rich, sodium-poor, fluid filling the cochlear duct (scala media) and bathing the stereocilia of hair cells; cf. perilymph.
Enhancement
In psychoacoustics, enhancement refers to the phenomenon of a brief increase in loudness for a new frequency or timbre added to a blend of frequencies or timbres. Enhancement is caused by adaptation to the earlier tones.
Entrainment
In biomusicology entrainment refers to the process of synchronizing neural or motor activity to an external rhythm.
Event Related Potential (ERP)
The electrophysiological response that is the direct result of a specific sensory, cognitive, or motor event. An ERP changes in response to changes in the stimulus.
Excitotoxicity
A pathological process whereby nerve cells are damaged or killed by excessive stimulation by excitatory neurotransmitters such as glutamate.
Exogenous
Having an external cause or origin; cf. endogenous.
Experimental Psychology
The branch of psychology concerned with the scientific investigation of basic psychological processes from sensation to cognition, usually employing animals and humans.
Explicit Learning (Explicit Knowledge)
Knowledge that is acquired through focused concentration, deliberate effort, and repetition is called “explicit” because it effort was made to acquire it. Examples include knowing how to write in cursive or play piano in the C minor scale. Compare with “implicit learning.”
Figure/Ground Illusion
A perceptual organization process that determines what is the figure (the central object of vision) and what is the ground (the background). Some visual scenes are ambiguous and the perception of what is figure and what is ground may be consciously flipped.
Fine Structure
Temporal fine structure refers to rapid oscillations close to the center frequency of a complex sound, in contrast to temporal envelope—the slower amplitude modulation of a sound wave over time. Fine structure is important in detecting pitch and melody information, while temporal envelope cues are important in speech recognition.
First-Order Beats
Amplitude fluctuations in a waveform’s envelope caused by two closely spaced frequencies interfering physically or mechanically at the source; c.f. second-order beats.
Fission
The action of dividing or splitting something into two or more parts. In auditory scene analysis, fission happens when one sound stream forms two or more streams when a property such as tempo, timbre, or pitch is changed. Fission is the opposite of fusion.
Form-Bearing Dimension
An element of an object that, if changed, changes the essence of the object such that it becomes a different one. Height is a form-bearing dimension for coffee mugs because if it is too short or too tall, the object cannot be labeled “coffee mug.” On the other hand, color is not a form-bearing dimension for coffee mugs because it can be changed without consequence.
Formant
A prominent frequency band that determines the phonetic quality of a vowel sound.
Fourier Transform (Fourier Analysis)
A mathematical function that deconstructs a complex wave to reveal its individual sine frequency components, their amplitudes and phase relationships.
Fractional Anisotropy (FA)
A measure of neural fiber integrity by diffusion tensor imaging (DTI) that reveals the directionality of fluids or liquid crystals. An FA value of 0 means that diffusion happens in no particular direction; a value of 1 means that diffusion is in only one direction.
Frequency
Referring to how often an event or a wave’s cycle repeats. Frequency is in an inverse relationship to time; the higher the frequency, the shorter its periodic cycle. Frequency is measured in cycles per second, or hertz (Hz).
Frontal Lobe
One of the four lobes of the brain; includes all of the cortex that lies anterior to the central sulcus and superior to the lateral fissure.
Functional Magnetic Resonance Imaging (fMRI)
A functional neuroimaging procedure that measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neural activity occur together.
Fundamental Frequency (f0)
The lowest frequency produced by a sound source, as distinct from the harmonics of
higher frequency components. It is typically, but not always, perceived as the pitch of a harmonic tone.
Fusion
The process or result of joining two or more things together to form a single entity. In auditory scene analysis, fusion happens when two or more sound streams form one stream when a property such as tempo, timbre, or pitch is changed. It is the opposite of fission.
Gauss (Gaussian Distribution)
The lower case word “gauss” is a measure of magnetic induction. It is commonly used in analog tape recording. The upper case “Gauss” refers to a normal or Gaussian distribution of data, named after the mathematician Karl Friedrich Gauss.
Gestalt Psychology
Gestalt psychology is a theory of mind of the 19th century Berlin School of experimental psychology. Gestalt psychology aims to describe the ability to acquire and maintain meaningful perceptions from stimulus elements such as color, shape, texture, pitch, tempo, etc. The central principle of Gestalt psychology is that an organized whole is more important than the sum of its parts.
Good Continuation
The Gestalt principle of good continuation is related to occlusion; objects are assumed to continue behind objects that block them and sounds are assumed to be continuous when they are momentarily interrupted.
Glottis
The part of the larynx that consists of the vocal cords and the small slit-like opening between them. The glottis expands and contracts to affect voice modulation.
Gray Matter
General term that describes regions of the central nervous system rich in neuronal cell bodies; it includes the cortices, cerebellum, and the central portion of the spinal cord.
Gyrus (pl. Gyri)
The ridges of the folded cortical layer of the brain.
Hair Cells
The sensory cells of the inner ear that transduce mechanical activity into electrochemical nerve spikes to produce the sensation of sound.
Harmonics
A whole-integer (n) numerical relationship between two frequencies. Sound sources that vibrate harmonically have partial frequencies that are n times the fundamental frequency f0. For example, if the f0 of a complex tone is 100 Hz and it has spectral energy at 200, 300, 400, 500 Hz and so on, the tone will be heard as harmonic and will have an easily perceived pitch. If the tone’s partial frequencies are not related to 100 Hz by whole numbers (for example, 183, 265, 333, 413 Hz), it is inharmonic and will not have an easily perceived pitch.
Head-Related Transfer Fuction (HRTF)
The ratio (usually expressed in dB) of the sound spectrum at the source to the sound spectrum reaching the tympanic membranes. The difference is a measure of the complex filtering action of the head and pinnae.
Helicotrema
A small hole at the apex of the cochlea between the scala vestibuli and scala tympani. It functions as a pressure vent to maintain equilibrium in the cochlea.
Heschl’s Gyrus
The primary auditory cortex; also called A1. The location of Brodmann’s areas 41 and 42. Heschl’s gyrus is the destination for auditory nerve fibers innervating the cochlea.
Heterogeneity
In music cognition, heterogeneity refers to hearing distinct timbres among a blend of instruments.
Higher-Order Perception
Referring to a perception that results from computational operations or cognitive functions performed by the brain. Higher-order integrative cortical areas, called association areas, intervene between the sensory inputs and motor outputs.
Higher-Order Unit
In cognitive psychology, higher-order unit refers to a whole percept that arises from individual parts, such as a word arising from letters, or a cup appearing from the conjunction of circular and cylindrical shapes.
Hippocampus
A cortical structure in the medial portion of the temporal lobe; in humans it is essential for memory formation, among many other functions.
Hyperacusis
Increased sensitivity or intolerance of typical environmental sounds, usually in a select frequency band of middle and upper-middle frequencies.
Hypothesis
A statement or proposed explanation for an observation, phenomenon, or a scientific problem that can be tested or observed. Hypothesis testing is a method for determining the measured value of a given parameter in a population; also called significance testing.
Identification
An additional component of a discrimination task requiring declarative memory to correctly label a stimulus or event.
Immunostaining
In biochemistry, Immunostaining is a technique for adding antibodies tagged with a staining medium (such as horseradish peroxidase) to specific tissues, cells, or structures. The colorized antibodies reveal the structures of interest when viewed under a light microscope.
Implicit Learning (Implicit Knowledge)
Knowledge that is acquired through passive exposure in the environment is called “implicit” because it did not arise through focused concentration or deliberate effort. Examples include knowing how to kick a ball or sing “Happy Birthday to You.” We do not need to be taught these things; we can just pick them up. Compare with “explicit learning.”
Incus
A small anvil-shaped bone in the middle ear, transmitting vibrations between the malleus and stapes bones.
Independent Variable (IV)
The variable that is manipulated in an experiment. In experimental designs it is the presumed cause of the behavior under observation. For example, presenting a click track at various tempos to see how well people can keep time to a beat. In this case the IV is tempo.
Inferior Colliculus
Nuclei (left, right) located in the midbrain innervating the thalamus and primary auditory cortex. Inferior colliculi receive neural signals directly from cochlear nuclei, superior olivary complexes, and somatosensory nuclei. It is the first higher-order processing stage in hearing.
Inharmonic
Referring to partial frequencies of a complex tone that are not related to the fundamental frequency (f0) by an integer (fn). Complex tones with inharmonic partials do not have an obvious pitch, e.g., bells, cymbals.
Innate
Inborn, natural, or present from birth.
Inner Ear
The bony labyrinth of the cochlea and semicircular canals that serve hearing and balance; it innervates cranial nerve VIII—the vestibulocochlear nerve.
Inner Hair Cells
In humans, mechanical activity from the basilar membrane causes electrochemical activity in a single row of approximately 3,500 inner hair cells (IHC) of the cochlea. Action potentials produced by IHCs send afferent signals up the auditory nerve bundle to reach the primary auditory cortex.
Integer Ratio
An integer is a whole number; a number that is not a fraction. Integer ratio refers to the quantitative relation between two amounts showing the number of times one value contains or is contained within the other.
Interaural Level Difference (ILD)
The intensity difference between the left and right ears from a sound wave that reaches both. ILDs are caused by diffraction—sound bending around obstacles in its path.
Interaural Phase Difference (IPD)
The difference in the phase angle of a singular sound wave or frequency components of a wave reaching the left and right ears. IPDs are caused by differences in the path length from the sound source to each ear.
Interaural Timing Difference (ITD)
The latency between sounds arriving at the left and right ears, caused by a source being positioned off-center.
Internal Clock
The internal clock is a metabolic set of functions that allow humans and other animals to keep track of time and sequential events and to coordinate their movements to external events. Theoretical models of the internal clock describe three distinct stages in which temporal information about an event is abstracted, encoded, and acted upon. The internal clock is implicated in attentional mechanisms because it alerts the system to expect the next event.
Inter-Onset Interval (IOI)
The duration of time between the onset of one stimulus or event and the onset of the next one.
Inter-Stimulus Interval (ISI)
The duration of time between the offset of a stimulus or event and the onset of the next one.
Ion Channel
Integral cell membrane proteins with pores that allow certain ions (charged particles) to diffuse across the membrane; ion channels permit depolarization of nerve cells, giving rise to action potentials.
Ipsilateral
Relating to or denoting the same side of the body from a particular structure or event; cf. contralateral.
Isochronous
Occurring at the same time or after the same interval of time, like a metronome, for example.
Just-Noticeable Difference (JND)
The smallest change in a stimulus parameter (e.g., frequency, brightness, weight) that can be detected by a perceiver. The jnd is relative, not absolute, for many properties so it is determined at a predefined level of performance. The jnd for frequency, for example, depends upon SPL and frequency range.
Kinetic Energy
The energy that a body possesses by virtue of being in motion.
Kurtosis
Refers to the sharpness of peaks in a frequency-distribution curve.
larynx
Also called the voice box, the larynx is the hollow muscular organ forming an air passage to the lungs and hold the vocal cords in humans and other mammals.
Lateral (Sylvian) Fissure
The anterior to posterior sulcus on each side of the brain that separates the frontal and temporal lobes.
Law of Prägnanz
‘Prägnanz’ is the German word for ‘pithiness’, which means ‘concise and meaningful’. It is the most general Gestalt principle, stating that perception will be the result of the simplest organization, requiring the least cognitive effort.
Limbic System
A term that refers to the cortical and subcortical structures concerned with the emotions. Prominent structures in the limbic system include: cingulate gyrus, hippocampus, amygdala, fornix, septum, and mammillary bodies.
Lobes
The four major divisions of the cerebral cortex: frontal, occipital, parietal, and temporal.
Long-Term Memory (LTM)
Robust, categorized information in the brain’s long-term storage. Long-term memories may not necessarily be immediately accessed but may appear under certain conditions. LTM is presumed to last indefinitely unless destroyed by brain damage or impairments such as dementia or Alzheimer’s disease.
Loudness
A psychological perception of the sound pressure level or intensity of an auditory stimulus. Loudness perception depends upon frequency range and the hearing sensitivity of the listener.
Magnetic Resonance Imaging (MRI)
A test that uses a magnetic field and pulses of radio wave energy to take pictures of organs and structures inside the body.
Malleus
A hammer-shaped small ossicle (bone) in the middle ear connecting the inner surface of the tympanic membrane (eardrum) to the incus.
Masking
Masking is the amount (or the process) by which the threshold of audibility for one sound is raised by the presence of another (masking) sound.
McGurk Effect
The McGurk effect is a perceptual phenomenon that demonstrates an interaction between hearing and vision in speech perception. The illusion occurs when the auditory component of one sound is paired with the visual component of another sound, leading to the perception of a third sound.
Melodic Contour
The up and down pattern of sequential pitch changes in a melody. Melodic contour is easier to process than specific interval information when learning new melodies.
Melodic Interval
An interval is the distance in scale steps between two pitches. A ‘melodic interval’ occurs when two tones are played in sequence, one after the other. Dyads and chords are ‘simultaneous intervals’ created when two or more tones are played at the same time.
Metabolite
A class of small molecules that assist an organism’s metabolic processes, including digesting food and expelling waste products.
Meter
The group of phenomena related to the musical measure. Meter consists of the hierarchical ordering of a piece of music into units of equal duration (beats). Metrically strong beats are often accented.
Midbrain
A structure at the topmost (or rostral) portion of the brainstem. The midbrain houses the superior and inferior colliculi and is important for vision, sound, sleep/wake cycles, and thermoregulation.
Middle Ear
The area between the tympanic membrane and oval window, comprising the ossicles and connecting structures. It functions as an impedance matching device to efficiently transfer airborne acoustic energy to the fluid-filled cochlea.
Minimum Audible Angle (MAA)
When the resolution of the auditory system is studied using stimuli presented via loudspeakers, the smallest detectable change in angular position, relative to the listener, is call the minimum audible angle.
Mismatch Negativity (MMN)
A component of the event-related potential (ERP) to an oddball stimulus in a sequence of stimuli. It arises from electrical activity in the brain and is studied within the field of cognitive neuroscience and psychology.
Modality
How something is done, how it happens, or how it is experienced. The visual modality, for example, refers to how something is seen.
Monaural
Referring to a sound delivered to one ear only.
Motor Mappings
In music cognition, the links between the primary, somatosensory, and auditory cortices that serve accurate musical performance.
Multidimensional Scaling (MDS)
Multidimensional scaling is a means of visualizing the level of similarity of individual cases of a dataset. It refers to a set of related ordination techniques used in information visualization, in particular to display the information contained in a distance matrix.
Music Cognition
The cognitive psychology of musical behaviors, including composing, singing, listening, memorizing, categorizing, interpreting, and performing music.
Myelin Sheath
The laminated wrapping that covers the axons of many nerve cells, formed by oligodendrocytes and Schwann cells. Its function is to speed the conduction of action potentials.
Nonisochronous
Occurring at irregular intervals of time.
Notch Filter
A region between two frequencies where the output is reduced or non-existent; also called a band-reject filter.
Novel/Familiar Paradigm
A cognitive task that taps implicit recognition memory for items. Unless items have been consolidated into long-term memory, novel/familiar paradigms test short-term memory capacity and perceptual fluency.
Nucleus (pl. nuclei)
Collections of nerve cells in the brain that are anatomically discrete and that typically serve a particular function.
Nucleus of the Lateral Lemniscus
An auditory processing stage fed from the superior olivary complex and feeding the inferior colliculus. Its function is not known, however it has good temporal resolution compared to other cells and is sensitive to both timing and amplitude changes in sound. The nucleus of the lateral lemniscus is also involved in the acoustic startle reflex.
Neural Architecture
Referring to the central nervous system’s immense array of nerve cells—the infrastructure or “hardware” where signals are expressed. Also called a neural network.
Object Representation
In cognitive psychology, object representation refers to the mental process that causes individual features of an object to be linked together to form the perception of a cohesive, whole item.
Observation
The first stage of the scientific method. Before testing an assumption it is necessary to discover what is already known of a phenomenon or organism. “Observation” can refer to a comprehensive literature search or field studies.
Oddball Stimulus
A strange or deviant stimulus presented in a sequence of regular, typical stimuli. The negative-going ERP wave within 100 to 200 ms after the oddball stimulus presentation is called the mismatch negativity (MMN).
Occipital Lobe
The posterior lobe of the cerebral hemisphere, it is primarily dedicated to vision processing.
Occlusion
Occlusion refers to an opaque object blocking out part of a second object (e.g., a car behind a tree). The Gestalt principle of good continuation allows us to imagine the parts of the car that we cannot see. In the visual modality occlusion provides information on depth perception.
Octave Equivalence
A subjective, behavioral phenomenon whereby an organism regards notes in a 1:2 frequency ratio relationship as being the same essential thing. For humans this means that tones separated by an octave are considered as being in the same musical pitch class.
Omega sign
The omega sign is an anatomical landmark distinguished by a curve in the central sulcus. Its shape develops as a function of hand movements.
Opiate Receptors
The sites in the brain, spinal cord, and digestive tract that receive endogenous opioids such as endorphins. These sites are linked to pain reduction and good feelings.
Ossicles
The three bones of the middle ear—malleus, incus, stapes—that are the smallest bones in the human body.
Otoacoustic Emission (OAE)
An otoacoustic emission is a sound generated inside the ear from the spontaneous or mechanically activated vibration of outer hair cells. OAEs are reduced or absent when inner hair cells are degraded, so the presence of OAEs is a sign of healthy hearing. OAEs are inaudible because they are below the threshold of hearing but can be measured with a tiny microphone in the ear canal. Their frequency range is typically around 1-3 kHz.
Outcome
In classical and operant conditioning, the consequence of responding to a stimulus.
Outer Ear
Referring to the auditory pathway from the external meatus (pinnae) and ear canal to the tympanic membrane (eardrum).
Outer Hair Cells
In humans, efferent signals from the auditory cortex cause electromechanical activity in a (mostly) triple row of approximately 12,000 outer hair cells (OHC) of the cochlea. OHCs expand and contract in response to action potentials, amplifying and attenuating activity on the basilar membrane and helping the listener to focus or ignore sound sources.
Oval Window
An oval-shaped membrane embedded in the cochlear shell, which connects the stapes of the middle ear to the basilar membrane.
p value
In statistics, the probability of obtaining results different from the reported value,
assuming that the null hypothesis is true. By convention, a p value of less than or equal to 5% (p < 0.05) is considered strong evidence against the null hypothesis, and therefore the observation may be assumed to be true with 95% or better confidence.
Parietal Lobe
The lobe of the brain that lies between the frontal lobe (anterior) and the occipital lobe (posterior), the parietal lobe is mainly responsible for motor skills and relaying inputs from the senses to muscle commands.
Partials
The spectral components of a complex sound; partials may or may not be harmonic.
Passive Process
In cognitive psychology, referring to a process that does not require attention, conscious participation, or an additional source of energy; cf. active process.
Peer Review
The final stage of the scientific method before publicizing experimental results. Research papers are subjected to scrutiny, critical commentary, and suggestions from the authors’ peers who have expertise in the paper’s topic.
Percept
A noun referring to the object that was perceived or the end stage of the perceptual process. It is customary in psychoacoustics to use the word “object” to refer to that which produces a sound and “event” as the perception of that object.
Perception
The organization, identification, and interpretation of stimuli such that they can be acted upon. Perception is influenced by the limits of the sensory systems (e.g., we cannot perceive ultraviolet light) and by cognitive processes such as attention, memory, learning, and expectations.
Perceptual Completion
Also called “filling-in,” perceptual completion is an optical illusion in which a boundary, color, texture, light, or object is seen where one does not actually exist.
Perceptual Fluency
Referring to the ease with which external items can be mentally processed. Perceptual fluency depends upon the item’s familiarity and complexity.
Perceptual Now
In Ernst Poppel’s (1994) experiments on time perception, “now” or the present moment is estimated to be 2-5 seconds in duration.
Perilymph
The potassium-poor, sodium-rich, fluid that bathes the bottom of cochlear hair cells as well as the scala tympani and scala vestibuli; cf. endolymph.
Periodic (Periodicity)
Appearing or occurring at regular intervals of time.
Periodicity Theory
The periodicity (also called temporal) theory of pitch perception states that pitch arises from the temporal pattern of auditory nerve firing in response to activity in the cochlea. According to periodicity theory, the pitch of a pure tone is determined by the rate of neuron firing patterns—either of single neurons, or neuron groups—locked to the wave’s cycle; cf. spectral theory.
Phase
The position in degrees or radians of a pressure wave or electrical signal at a specific point in time. When two sound waves of the same frequency are added in phase, their peaks combine to form a higher-amplitude signal. When two sound waves of the same frequency are added 180° out of phase, their peaks cancel each other out and the net amplitude is zero.
Phase-Locking
A phase-locked system generates an output signal that is related to the phase of the input signal. Many nerves innervating inner hair cells, for example, exhibit phase-locking and fire once per cycle of cell activity.
Phenomenon (Phenomenological States)
In science, a phenomenon is an event that manifests or shows itself and can be measured. It appears as an ultimate change in an organism as a result of mental processing. Phenomenal states also include feelings, desires, motives, moods, and thoughts.
Pink Noise
Noise containing many or all frequencies at equal power per octave. Compared with the brighter-sounding white noise, pink noise is balanced across the frequency spectrum with equal amounts of low, mid, and high frequencies.
Pinna (pl. pinnae)
The external meatus or visible part of the ear
Pitch
The psychological property of periodic sounds that allows them to be ordered from low to high on a musical scale. Pitch is different from frequency in that pitch is a subjective categorical perception depending on the perceiver and musical tonal theory.
Pitch Chroma
Referring to the 12 note names of the Western pitch classes—A, A#, B, C, C#, D, D#, E, F, F#, G, G#. ‘Chroma’ typically refers to the purity or intensity of a color.
Pitch Height
Referring to a tone’s position on a continuum from low to high frequency.
Pitch of the Missing Fundamental (Virtual Pitch; Residue Pitch)
The phenomenon of perceiving pitch at the fundamental frequency (f0) of a complex tone, even when the f0 is absent. The brain perceives the pitch of a complex tone not only by its f0, but also by the periodicity implied by the frequency separating the higher harmonics; we may perceive the same pitch (perhaps with a different timbre) even if the f0 is missing.
Plasticity (Neuroplasticity)
The reorganization of neurons and their support systems as a function of development and learning. Neuroplasticity takes place over a lifetime but is most active in infants and young animals.
Place Coding (Place Theory)
Another name for the spectral theory of pitch perception, so-called because it is based on the frequency-to-place mapping or tonotopicity of the inner ear.
Polarized (Polarity)
A state of having two conditions across a boundary, such as different electrical charges or ion concentrations across two sides of a membrane. Also, referring to a continually graded organization along one of the major axes of an animal, such as anterior and posterior.
Posterior
Towards the back of an animal or structure. Posterior may be used as a synonym for caudal or dorsal.
Potential Energy
The energy possessed by a body by virtue of its position relative to others, stresses within itself, electric charge, and other factors.
Power Law of Learning
The power law states that the logarithm of the reaction time for a particular task decreases linearly with the logarithm of the number of practice trials taken. The function describes the shape of the learning curve, which is very high initially but decreases rapidly after repeated practice.
Pre-Attentive
Pre-attentive processing is the subconscious accumulation of incoming sensations from internal and external environments. Perception, attention, knowledge, expectations, contexts, and conscious awareness all contribute to the next processing stage—filtering incoming sensations to allow an organism to attend to what is important. Information with the highest salience or most immediate relevance may be selected for further processing.
Precedence Effect
When two sounds from two locations reach the ears in quick succession, the source will be perceived as coming from where the first sound originated. This is also called the “Haas effect” or “law of first wavefront.”
Presbycusis
Literally “old hearing,” presbycusis is the loss of hearing that gradually occurs in most individuals as they grow older.
Presbyopia
Literally “old eyesight,” presbyopia is the loss of focus and contrast that gradually occurs in most individuals as they grow older.
Primary Auditory Cortex
The major cortical target of the auditory nerve bundle, the primary auditory cortex or A1 is located in the superior temporal gyrus. Its frequency response properties are organized such that there is a one-to-one frequency map on A1 corresponding to the tonotopic organization of the basilar membrane. Low frequencies are processed anterolaterally; high frequencies are processed more deeply in the lateral fissure, posterior to the low frequency region.
Primary Motor Cortex
The major source of descending projections to the motor neurons in the spinal cord and cranial nuclei, it is located just anterior to the central sulcus.
Principal Components Analysis (PCA)
Principal component analysis (PCA) is a statistical procedure that converts a large set of data into a smaller set of uncorrelated variables called “principal components.” It is useful in marketing and social science research to identify the most important dimensions along which items in large sets vary from one another.
Probability Mass Function (PMF)
Probability Mass Function (PMF) is an analysis of the probability of hard clipping and soft distortions in an audio sample. It reports an “amplitude histogram” or the likelihood of a discrete random variable such as a clipped peak occurring at discrete values.
Prosody
The pattern of stress and intonation that gives spoken language its nuance. For example, questions typically rise in pitch at the end while commands typically fall in pitch.
Proximity
The Gestalt principle of proximity states that objects or events that are physically or temporally close to one another are assumed to belong together.
Psychoacoustics
The branch of psychology concerned with the perception of sound and its physiological effects.
Psychophysics
The branch of psychology that deals with the relationships between physical stimuli and their mental representation in terms of sensation and perception. “Psychophysics” also refers to the methods used to study perception.
Psychophysical Tuning Curves (PTC)
The curve showing the level of a narrowband masker needed to mask a fixed sinusoidal signal, plotted as a function of the masker frequency. PTCs are level-dependent and asymmetrical and reveal the shape of auditory filters as a function of frequency and loudness.
Pure Tone
Pure tone is another term for sine wave. It is pure because it consists of only one frequency.
Rarefaction
In wave theory, “rarefaction” refers to a region of low pressure or density, the opposite of compression or condensation.
Research Question
A primary unknown question that justifies a research project. A hypothesis is formed in relation to the research question.
Relative Pitch (RP)
The ability to perceive and remember pitches by their relationship to other pitches in a scale or key. Relative pitch processing allows humans to recognize that transposed melodies are the same essential thing.
Repetition Pitch
Amplitude-modulated noise or intermittent signals can be heard as pitched if their repetition rate is in the range where pitch perception is strong.
Resolve
In psychoacoustics to “resolve” or “hear out” means to isolate and attend to the individual components of a complex wave. It is easier to resolve frequency components that are not within a single critical band.
Response (Bias)
In learning theories, a response is the measured behavior that follows a stimulus or antecedent and precedes an outcome or consequence. Response bias is an individual’s tendency to be more willing to reply “yes” or “no” on a majority of trials.
Response (Criterion)
In signal detection theory, the response criterion (c) is a number representing response bias or tendency to respond “yes” or “no” on any given trial. An ideal participant has a response criterion of 0, meaning no bias.
Resting Arousal Rate
Also called baseline arousal rate, it refers to an organism’s autonomic nervous system activity (e.g., heart rate, digestion rate, breathing, blood pressure) when not active or stimulated. It is a measure of the organism’s readiness to respond to changes in the environment and is linked to personality types (e.g., introvert vs. extravert) and preferences.
Resting Potential
The electrical charge of a neuron relative to its surroundings when not stimulated or involved in passing an action potential—its “quiescent state.”
Roughness
The quality of having an uneven or bumpy surface (i.e., not smooth). Auditory roughness refers to two combined tones with a frequency difference between 15 and 200 Hz. The resultant amplitude modulation is perceptible as a course or bumpy sonic texture. Roughness contributes to the perception of sensory dissonance.
Sagittal
The sagittal anatomical plane divides the body or brain into left and right parts. A sagittal view of the brain is a cutaway of either the left or right hemisphere.
Salient (Salience)
The most noticeable or important item or sensation.
Scatterplot
Also called an XY plot or scatter diagram, this graph shows how two variables are related to each other by plotting each observation on both the x- and y-axis to reveal a pattern of correlation. Weight as a function of height could be plotted on a scatterplot.
Schema (pl. schemata)
A representation of a plan or theory in the form of an outline or model: a schema of scientific reasoning. A schema is a mental scaffold supporting factual knowledge and examples for a given concept.
Scientific Method
A method or procedure that has characterized natural science since the 17th century, the scientific method comprises systematic observation, measurement, experiment, and the formulation, testing, and modification of hypotheses.
Segregation
In auditory scene analysis, “segregation” refers to the ability to hear the individual sources in a combined sound.
Semicircular Canals
Three looping, fluid-filled tubes joined to the bone that forms the cochlea. The semicircular canals house the sensory receptors of the vestibular system. It provides the brain with information on head position with respect to three axes — pitch (nose up or down), roll (nose vertical or horizontal), and yaw (nose left or right).
Semi-Permeable Outer Membrane
Referring to the outer membrane of a cell, semi-permeable cells are selective for certain particles, ions, or water, thus they respond only to some stimuli and typically have a threshold for activation.
Semitone
The smallest interval used in classical Western music, equal to a twelfth of an octave or half a tone; a half step.
Sensation
The conversion of energy from the environment into a pattern of response by the nervous system.
Sensorineural Hearing Loss
Diminished sense of hearing due to damage to the inner ear or its related auditory structures. This is in contrast to conductive hearing loss caused by damage to outer or middle ear structures.
Short-Term Memory (STM)
Memories that last from seconds to minutes, corresponding to the active trace generated by a stimulus or event. STM is passive and will degrade when new stimuli are encountered, or merely as a function of time.
Signal Detection Theory (SDT)
Signal detection theory is a general psychophysical approach to measuring performance. It is used to determine the ability to differentiate between information-bearing patterns (i.e., the signal) and random patterns that distract from the information (i.e., the noise).
Similarity Matrix
A 3D map of psychological space that reflects the degree to which objects are perceived to be different from each other. Objects may be very similar in one dimension, such as color, but very different in other dimensions, such as shape or size.
Sine Wave (Pure Tone)
A mathematical curve that describes a smooth repetitive oscillation. It is named after the function sine. In psychoacoustics a sine wave is also called a pure tone because it has only one frequency component; cf. complex wave.
Skin Effect
The tendency for high frequencies to be conducted along the surface layer of wires and nerve bundles. Low frequencies, in contrast, travel through the entire diameter.
Somatosensory Cortex
The region of the cerebral cortex just posterior to the central sulcus, the somatosensory cortex receives neural projections from the body, muscles, and joints.
Sound Pressure Level (SPL)
Sound pressure level refers to a change in the ambient atmospheric pressure caused by a vibrating object that displaces air, water, or other molecules. For humans SPL is most relevant in the audible range of roughly 30 to 17,000 Hz. SPL is measured in decibels (dB). The human threshold of hearing is 0 dB SPL and the threshold of pain is 130 dB SPL.
Spatial Localization (Lateralization)
The ability to identify the location of a sound source in 3D space relative to the listener: elevation (height), azimuth (left vs. right; front vs. back), and distance. Localization refers to the position of an external sound source; lateralization refers to the position of an apparently internalized sound source delivered via headphones.
Spectral Centroid
The weighted center of a complex tone in terms of frequency; the frequency band where most of the tone’s energy is located.
Spectral Flux
Flux means change; spectral flux refers to how amplitude and phase of a complex tone’s frequency components change with respect to each other over time. Different classes of musical instruments exhibit different patterns of spectral flux, thus it provides a psychoacoustic cue for instrument identification.
Spectral Theory
The spectral (also called place) theory of pitch perception links it to the frequency components of a tone and the corresponding place(s) of activation on the basilar membrane where those components reach their highest peak(s). The theory is built upon the observation that the cochlea and auditory path exhibit tonotopicity—frequencies in the audible range are mapped to specific locations.
Spectrogram
A spectrogram is a visual representation of the frequencies that make up a sound, from low to high on the y-axis, and how they change over time, from left to right on the x-axis.
Spectrum (Spectral Character)
The distribution of frequency components of a sound or light wave. All complex tones are comprised of multiple frequencies, thus a complex tone can be deconstructed and described by its frequency spectrum.
Spiral Ganglion
A term for the auditory nerve bundle of cranial nerve VIII. It is so-called because it exits the spiral-shaped cochlea.
Spontaneous Firing Rate
In neuroscience spontaneous firing rate refers to how often a nerve cell discharges an action potential in the absence of a stimulus; also called “resting arousal rate.”
Stapes
A small stirrup-shaped bone in the middle ear that connects to the oval window for transmitting vibrations to the basilar membrane of the cochlea.
Statistical Significance
A decision made in hypothesis testing when the p value is less than a pre-determined level (typically 0.05 but can be less, depending upon experimental design). When the null hypothesis is rejected, the observation is said to reach significance, meaning that the observed effect is true and replicable and the chances of error are minimal.
Stereocilia
Along with kinocilium, stereocilia form the hairs extending from the apical end of hair cells. Their movement induces mechanotransduction—motion converted to an action potential.
Stimulus
A thing or event of sufficient strength to provoke a response in an organism, organ, or tissue. In learning paradigms, the stimulus may be referred to as the antecedent because it precedes a response or behavior.
Stimulus-Response Matrix
A display of the relationship between a stimulus and the effector’s response to it. Each cell in the matrix contains numbers representing correct responses, false alarms, misses, and correct rejections. It is useful for calculating the probability that the effector will detect the signal on a given trial.
Stochastic
Having random probability distribution or a pattern that can be analyzed statistically but not predicted accurately. An example is an ocean wave.
Streaming
The perception of two or more tone sequences that seem to come from one singular source.
Stria Vascularis
A striated membrane in the scala media of the cochlea. Its function is to produce endolymph and transport potassium for nerve spike induction. Its degeneration due to age is implicated in age-related hearing loss.
Sulcus (pl. Sulci)
The folds or valleys of the folded cortical layer of the brain.
Superior Colliculus
Laminated structure at the top of the midbrain, just above the inferior colliculus; the superior colliculus plays an important role in orienting movement of the head and eyes.
Superior Olivary Complex (SO)
The auditory brainstem structure after the cochlear nuclei and before the nucleus of the lateral lemniscus. The SO processes intensity and timing differences between the left and right ears, mediating spatial localization.
Synapse
The junction between adjacent neurons into which neurotransmitters are released. The presence of neurotransmitters in the synapse may excite or inhibit adjacent neurons.
Synaptic Ribbons
Synaptic ribbons are electron-dense structures arrayed along the interior terminal end of inner hair cells. Their function is to hold vesicles that release neurotransmitters into the synapse, allowing exceptionally fast firing.
Synaptopathy
A dysfunction of synapses due to disease or prolonged excitotoxicity at the synaptic junction.
Synthetic Listening
In music, the tendency to focus on the global whole or gist of combined pitches, sequential chords, harmonies, timbres, and other components of a musical signal.
Tectorial Membrane
The fibrous sheet overlying the apical surface of the cochlear hair cells; it produces a shearing motion against the stereocilia of outer hair cells when the basilar membrane moves up and down. This contact assists the outer hair cells in amplifying and attenuating cochlear movement.
Temporal
Referring to time and sequences of events
Temporal Coding (Temporal Theory)
Another name for the periodicity theory of pitch perception, so-called because it links pitch perception to the ability to compute timing regularities in periodic sections of a waveform.
Temporal Envelope
A term used to describe the overall amplitude changes of a sound wave as it unfolds over time; cf. fine structure.
Temporal Integration
Referring to the dependence of loudness perception on a signal’s duration. Loudness perception grows during a sound’s first 200 ms or so.
Temporal Lobe
One of the four lobes of the human brain, below the frontal lobe and the lateral fissure; site of the primary auditory cortex and speech processing regions. The word “temporal” refers to timing.
Temporary Threshold Shift
A temporary reduction in the apparent loudness of sounds due to auditory fatigue. Hearing thresholds typically recover within 24 hours.
Timbre
A physical and psychological property of sounds. Timbre refers to the tone color (i.e., quality) of voice or musical instruments that allows them to be heard as distinct from each other when they are speaking the same words or playing the same note.
Timbre Space
Referring to the psychological distance between two distinct instruments or voices. As timbres become more similar, the timbre space between them gets smaller.
Timbre Template
A template serves as a model or pattern for others to copy; timbre template refers to the mental process of interpolating what an instrument or voice should sound like across its entire range, once its timbre has been learned at a few pitches.
Tinnitus
A ringing, buzzing, chirping, distortion or other phantom sound with no external source. Tinnitus can be continuous or intermittent; it can occur in one or both ears. The cause is typically inner ear damage but it can also originate in the cortex. There is presently no cure for tinnitus although some behavioral treatments can reduce its severity.
Tip Link
Filament structures shaped like springs that connect adjacent stereocilia; they mediate the gating of hair cells’ conducting channels.
Tonal Hierarchy (Tonality)
Tonality is a musical system that arranges pitches or chords according to their importance in a given scale or key. Tonal hierarchy is a relative, not absolute, system governed by modes (e.g., Ionian, Dorian, etc.) and scales (e.g., major, minor).
Tonotopicity
The distribution of frequency activity across the surface of a structure. Tonotopicity originates on the basilar membrane and is preserved in ascending auditory structures, including the auditory cortex.
Top-Down
Information processing that begins with knowledge of a stimulus that assists in the perception of an object. It is sometimes referred to as “knowledge-driven processing” because it takes as a starting point the context and likelihood of a stimulus being a certain thing; cf. bottom-up.
Tractography
A 3D modeling technique used to visually represent neural tracts using data collected by diffusion tensor imaging (DTI). Tractography uses special techniques of magnetic resonance imaging (MRI) and computer-based image analysis.
Transient
A portion of a wave that does not repeat and therefore does not have a musical pitch.
Traveling Wave
A wave in which the medium moves in the direction of propagation, like a wave caused by flicking a rope. Pressure variations in the ear canal cause amplitude variations in the basilar membrane, starting at the base (at the oval window) and traveling towards the apical or far end of the cochlea.
Two-Alternative Forced-Choice (2AFC)
A 2AFC experimental design presents stimulus 1 and stimulus 2 to participants and asks them to choose the correct response to questions such as, “which one is louder?” or, “which one is familiar?”
Tympanic Membrane
The eardrum—a thin membrane separating the outer ear canal and the malleus of the middle ear.
Variable
An element, characteristic, or factor that is measurably different across individuals or stimuli.
Vesicle
Literally, a small sac. Vesicles are organelles that store and release transmitters at nerve endings.
Virtual Pitch
Virtual pitch is also called “residue pitch” or “pitch of the missing fundamental.” Complex tones with harmonic partials provide the brain with enough information that it can deduce the fundamental frequency for accurate pitch perception, even in cases where the fundamental is missing.
Voxel-Based Morphometry (VBM)
Voxel-based morphometry is a neuroimaging technique that compares brain anatomy among many individuals. VBM registers every brain to a template, which gets rid of most of the large differences in brain anatomy among people. Then the brain images are smoothed so that each voxel represents the average of itself and its neighbors. Finally, the image volume is compared across brains at every voxel.
Weber’s Law
Weber’s Law shows that the amount of detectable change in a stimulus is relative, not absolute. The value of a change in intensity (ΔI) divided by a baseline intensity (I) is called the “Weber fraction.” The Weber fraction was once thought to be a constant for different stimuli such as light, temperature, loudness, weight, etc., but it has since been shown that the fraction is not constant, i.e., the law does not hold, at all baseline intensities.
White Matter
A general term to refer to large axon tracts in the brain and spinal cord; the phrase derives from the fact that axonal tracts have a whitish color.
White Noise
Noise containing many or all frequencies at equal amplitude.
Working Memory (WM)
Working memory is a theoretical framework referring to structures and processes used for temporarily storing and manipulating information. Working memory equals short-term memory plus a mental operation. The term working memory is sometimes used synonymously with short-term memory, but the two concepts are distinct. Short-term memory usually refers to a passive process of short-term information storage, and does not entail manipulating or organizing active neural traces.
Medial Geniculate Nucleus
Located in the medial region of the left and right thalamus, this nucleus is a major relay
for auditory information between the brainstem and cortex. It is adjacent to the lateral
geniculate nucleus that performs the same function for visual input.
