Ch. 10 and 11 Flashcards
two potential types of information for determining the source of a sound (auditory localization cues)
- pressure waves of sound do not reach both ears at the same time → sounds arrive very slightly sooner at the ear closer to the source
- The intensity of sound is greater at the ear closer to the source
interaural time difference (ITD)
the difference in time between arrivals of sound at one ear versus the other
azimuth
the angle of a sound source on the horizontal plane relative to a point in the center of the head between the ears; measured in degrees, with 0 degrees being straight ahead; angle increases clockwise toward the right, with 180 degrees being directly behind
medial superior olives (MSO)
a relay station in the brainstem where inputs from both ears contribute to detection of the interaural time difference; first places in the auditory system where inputs from both ears converge
interaural level difference (ILD)
the difference between levels (intensities) of sound at one ear versus the other
properties of ILD
- Sounds are more intense at the ear that is closer to the sound source and less intense at the ear farther away from the source
- The ILD is largest at 90 and -90 degrees; it is nonexistent at 0 degrees (directly in front) and 180 degrees (directly behind)
- Between these two extremes, the ILD correlates with the angle of the sound source but because of the irregular shape of the head, the correlation is less precise than it is with ITDs
difference between ITD and ILD
the head blocks high-frequency sounds much more effectively than it does low-frequency sounds
- ILDs are greatest for high-frequency tones
- ILDs are greatly reduced for low frequencies
lateral superior olive (LSO)
a relay station in the brainstem where inputs from both ears contribute to detection of the interaural level difference
cone of confusion
a region of positions in space where all sounds produce the same time and level (intensity) differences (ITDs and ILDs); extends perpendicularly from the left or right ear
pinnae and head cues
- Due to the shape of the pinna, they funnel certain sound frequencies more efficiently than others
- The size and shape of the rest of the body, especially the upper torso, affect which frequencies reach the ear most easily
- Due to these effects, the intensity of each frequency varies slightly according to the direction of the sound
anechoic room
room in which the walls are padded so that sounds do not bounce off the walls
measure how effects of pinnae and upper body shapes by having listeners sit in an anechoic room
- Anechoic room is filled with speakers at locations up, down, and all around the listener
- Insert microphones next to the person’s eardrums and play sounds from different points in space to measure how much energy from different frequencies actually reaches the eardrums from different locations
directional transfer function (DTF)
a measure that describes how the pinna, ear canal, head, and torso change the intensity of sounds with different frequencies that arrive at each ear from different locations in space (azimuth and elevation)
- as they grow, children may update the way they use DTF information
auditory distance perception
listeners are best at judging the distance to a sound source when it is about 1 meter away
relative intensity
- Cue for judging distance of a sound
- Sounds become less intense with greater distance
- Interpreting this cue requires one to make assumptions about the sound sources that may turn out to be false
- Inverse-Square Law
- intensity and movement work as a distance cue similar to motion parallax in depth perception because sounds that are farther away do not seem to change direction in relation to the listener as much as nearer sounds do
inverse-square law
a principle stating that as distance from a source increases, intensity decreases faster such that decrease in intensity is equal to the distance squared
spectral composition
Sound-absorbing qualities of air dampen high frequencies more than low frequencies, so when sound sources are far away, higher frequencies decrease in energy more than lower frequencies as the sound waves travel from the source to the ear
- analogous to the visual depth cue of aerial perspective
harmonic spectrum
the spectrum of a complex sound in which energy is at integer multiples of the fundamental frequency
- lowest frequency is the fundamental frequency
- perceived pitch is determined by the fundamental frequency and the harmonics add to the perceived richness of the sound
fundamental frequency
the lowest frequency component of a complex periodic sound (harmonic spectrum)
missing fundamental frequency in harmonic spectrum
If the fundamental frequency is removed from a series of harmonics and only the others are presented, the pitch that listeners hear corresponds to the fundamental frequency
timbre
the psychological sensation by which a listener can judge that two sounds with the same loudness and pitch are dissimilar
attack
the part of a sound during which amplitude increases (onset)
decay
the part of a sound during which amplitude decreases (offset)
auditory scene analysis
processing an auditory scene consisting of multiple sound sources into separate sound images
spatial separation between sounds
- Sounds that emanate from the same location in space can typically be treated as if they arose from the same source
- In a natural environment in which sound sources move, a sound that is perceived to move in space can more easily be separated from background sounds that are relatively stationary
- If sound stays in the same place relative to the path of a listener, it will be easier for that sound to be sorted out from other sounds (listeners can move)
spectral/temporal qualities
Sounds with the same pitch or similar pitches are more likely to be grouped as coming from the same source and to be segregated from other sounds
auditory stream segregation
the perceptual organization of a complex acoustic signal into separate auditory events for which each stream is heard as a separate event
similarity
Gestalt grouping rule stating that the tendency of two sounds to group together will increase as the acoustic similarity between them increases
grouping by timbre
When a sequence of tones that have increasing and decreasing frequencies is presented, tones that deviate from the rising/falling pattern are heard to “pop out” of the sequence
grouping by onset
- Sound components that begin at the same time tend to be heard as coming from the same sound source
- common fate
common fate
Gestalt grouping rule stating that the tendency of sounds to group together will increase if they begin and/or end at the same time
when sounds become familiar
Listeners make use of experience and familiarity to separate different sound sources
good continuation
Gestalt grouping rule stating that sounds will tend to group together as continuous if they seem to share a common path, similar to a shared contour for vision
acoustic startle reflex
the very rapid motor response to a sudden sound; very few neurons involved in the basic startle reflex, which can also be affected by emotional state
inattentional deafness
the failure to notice a fully-audible, but unexpected sound because attention was engaged on auditory stream
cost to moving attention from one sound source to another
listeners become less accurate in understanding what they hear when they have to switch between talkers
pitch
the psychological aspect of sound related mainly to perceived frequency
octave
the interval between two sound frequencies having a ratio of 2:1
just intonation
frequencies of sounds are in simple ratios with one another
equal temperament
frequencies of notes are adjusted slightly from simple ratios so that combinations of notes will sound equally good when played in higher- or lower-frequency ranges
tone height
a sound quality corresponding to the level of pitch
tone chroma
a sound quality shared by tones that have the same octave interval
can visualize musical pitch as a helix
- Frequency and tone height increase with increasing height on the helix
- The circular laps around the helix correspond to changes in tone chroma
- At the same point along each lap around the helix, a specific sound lies on a vertical line, and all sounds along that line share the same tone chroma and are separated by octaves
chord
a combination of three or more musical notes with different pitches played simultaneously
consonant
combinations of notes in which the ratios between the note frequencies are simple
- perceived to be most pleasing
- octave
dissonant
less elegant ratios of note frequencies
- do not sound very pleasing
- minor second and augmented fourth
absolute pitch (AP)
a rare ability whereby some people are able to accurately name or produce notes without comparison to other notes
relative pitch
when people identify notes relative to one another
melody
a sequence of notes or chords perceived as a single coherent structure
contour
the pattern of rises and declines in pitch
tempo
the perceived speed of the presentation of sounds
rhythm
a repeated pattern of sounds comprised of strong and weak elements
listeners are predisposed to grouping sounds into rhythmic patterns
- conducted experiments in which he played a sequence of identical sounds perfectly spaced in time so that they had no rhythm
- Listeners readily reported that the sounds occurred in groups of two, three, or four
- They reported hearing the first sounds of a group as accented while the remaining sounds were unaccented
syncopation
any deviation from a regular rhythm
compared with other animals, the human larynx is positioned quite low in the throat
- One disadvantage of such a low larynx is that humans choke on food more easily than any other animal does
- The fact that these life-threatening anatomical liabilities were evolutionarily trumped by the survival advantage of oral communication is a testament to the importance of language to human life
production of speech has three basic components
- respiration –> lungs
- phonation –> vocal folds
- articulation –> vocal tract
respiration and phonation
- To initiate a speech sound, air must be pushed out of the lungs, through the trachea, and up to the larynx
- The diaphragm flexes to draw air into the lungs and elastic recoil forces air back out
- At the larynx, air must pass through the two vocal folds, which are made up of muscle tissue that can be adjusted to vary how freely air passes through the opening between them
vocal folds
the pair of elastic tissues that vibrate due to airflow generated by lungs, depending on how close or apart and how tense or lax they are
phonation
the process through which vocal folds are made to vibrate when air pushes out of the lungs
vocal folds differ by age and gender
- Children, who have relatively small vocal folds, have higher-pitched voices than adults do
- Adult men generally have lower-pitched voices than adult women because one of the effects of testosterone during puberty is to increase the mass of the vocal folds
vocal tract
the airway above the larynx used for the production of speech; includes the oral tract and nasal tract
articulation
the act or manner of producing a speech sound using the articulators— vocal tract structures including the mouth, tongue, soft palate, and jaw
resonator
most objects such as musical instruments and vocal tracts are resonators because, due to their shape, they increase amplitude at some frequencies, called resonant frequencies, compared to other frequencies
formant
a resonance of the vocal tract; specified by their center frequency and are denoted by integers that increase with relative frequency
spectrogram
in reference to sound analysis, a three-dimensional display that plots time on the horizontal axis, frequency on the vertical axis, and amplitude (intensity) on a color or gray scale
production of vowels
made with a relatively open vocal tract and they vary mostly in how high or low and how far forward or back the tongue is placed in the oral tract, along with whether or not the lips are rounded
production of consonants
obstructing the vocal tract in some way
each consonant sound can be classified according to three articulatory dimensions
- place of articulation –> airflow can be obstructed: at the lips, at the alveolar ridge just behind the teeth, at the soft palate
- manner of articulation –> airflow can be: totally obstructed, partially obstructed, only slightly obstructed, first blocked adn then allowed to sneak through, blocked at first from going through the mouth but allowed to go through the nasal passage
- voicing –> the vocal folds may be: vibrating, not vibrating
coarticulation
the phenomenon in speech whereby attributes of successive speech units overlap in articulatory or acoustic patterns; production of one speech sound overlaps the production of the next
categorical perception
for speech as well as other complex sounds and images, the phenomenon by which the discrimination of items is little better than the ability to label items
three qualities define categorical perception
- A sharp labeling (identification) function
- Discontinuous discrimination performance
- Ability to discriminate sounds can be predicted by how listeners label the sounds
“motor theory” of speech perception
processes used to produce speech sounds can somehow be run in reverse to understand the acoustic speech signal; we perceive speech sounds by recognizing the articulatory gestures or movements used to produce them, rather than by simply analyzing the acoustic properties of the sounds
coarticulation and spectral contrast
- Coarticulation always causes a speech sound to become more like the previous speech sound, auditory processes that enhance the contrast between successive sounds undo this assimilation
- Spectral contrast helps listeners perceive speech, despite the lack of acoustic invariance due to coarticulation
speech in the brain
- Hearing sounds of any kind activates the primary auditory cortex (A1)
- Processing of complex sounds relies on additional areas of cortex adjacent to A1 (belt and parabelt areas)
- there are areas of the motor cortex that becme active when listening to speech
