Lecture 12 Flashcards
Sound
Comes from pressure fluctuations in the air
Sound pressure (Pascals)
Measures force exerted by air molecules
Loudness
Psychological perception of sound intensity
Decibels (dB)
Measures loudness. Relative to the smallest perceivable pressure
0 dB doesn’t mean 0 sound
Represents the minimum audible level
Logarithmic Scaling
+10 dB = 10 x increase in intensity
-E.g. the sound of a helicopter is 10x more intense than the sound of a hairdryer
Pitch
The psychological aspect of sound related mainly to the fundamental frequency
Equal-Loudness Curve
A graph plotting sound pressure level (dB SPL) against the frequency for which a listener perceives constant loudness
-E.g. sounds of 70 dB at 0.2 kHz and 60 dB at 1kHz will sound equally loud (60 photons)
Harmonic Spectrum
The spectrum of a complex sound in which energy is at integer multiples of the fundamental frequency
-Typically caused by a simple vibrating source
Fundamental Frequency
The lowest-frequency component of a complex periodic sound
Timbre
The psychological sensation by which a listener can judge that 2 sounds with the same loudness and pitch are dissimilar
-Timbre quality is conveyed by the profile of the harmonics
-E.g. 2 voices can measure the same loudness + pitch, but sound different
Auditory Canal
A tube-like structure that directs sound waves from the outer ear to the tympanic membrane (eardrum)
Tympanic Membrane (Eardrum)
A thin, vibrating membrane that separates the outer ear from the middle ear and transmits sound vibrations to the ossicles
Ossicles
3 small bones in the middle ear (malleus, incus, and stapes) that amplify and transmit sound vibrations to the inner ear
Cochlea
A spiral-shaped, fluid-filled structure in the inner ear that converts sound vibrations into neural signals for hearing
Oval Window
A membrane-covered opening that connects the midle ear to the cochlea, transmitting vibrations from the ossicles
Round Window
A flexible membrane in the cochlea that helps relieve pressure from sound waves travelling through the cochlear fluid
Cochlear (Auditory) Nerve
The nerve that carries auditory information from the cochlea to the brain for sound processing
Organ of Corti
A structure on the basilar membrane of the cochlea that is composed of hair cells and dendrites of auditory nerve fibers
Basilar Membrane
A structure within the cochlea that vibrates in response to sound and plays a key role in frequency discrimination by supporting hair cells
Tectorial Membrane
A gelatinous membrane in the cochlea that interacts with hair cells, aiding in the conversion of mechanical sound vibrations into electrical signals
Hair Cells
Sensory receptor cells in the cochlea that detect sound vibrations and convert them into neural signals transmitted to the brain via the auditory nerve
Place Code
Identifies each pitch with a particular place along the basilar membrane.
-Lower frequencies travel further
-Higher frequencies closer the outside
Temporal Coding
Auditory nerve firing is also ‘‘phase-locked’’, i.e. neurons systematically fire at a given time point of the cycle
-However, above 4000Hz-5000Hz the refractory period of AN fibers doesn’t allow neurons to fire fast enough
Volley Principle
Even if individual auditory nerve fibers can’t keep the pace, the whole population of neurons can still temporally encode the frequency
Cochlear Nucleus
The first brainstem region that receives auditory signals from the cochlea, where initial sound processing occurs
Superior Olive
A brainstem structure involved in sound localization by comparing timing and intensity differences between ears
Inferior Colliculus
A midbrain structure that integrates auditory information from various brainstem nuclei and plays a role in reflexive responses to sound
Medial Geniculate Nucleus (MGN)
A relay station in the thalamus that processes and transmits auditory information to the primary auditory cortex
Primary Auditory Cortex
The region of the cerebral cortex responsible for processing and interpreting sound information, located in the temporal lobe
Tonotopy
The spatial organization of sound frequency processing in the auditory system, where different frequencies are mapped to specific locations along the cochlea and auditory cortex
Belt Region
A secondary auditory area surrounding the primary auditory cortex that processes more complex sounds like speech
Parabelt Region
A higher-order auditory processing area adjacent to the belt region that processes more complex sounds like speech
'’Where’’ Pathway
The dorsal stream of auditory processing that helps determine the location and mouvement of sounds, connecting auditory areas to the parietal lobe
'’What’’ Pathway
The ventral stream of auditory processing that identifies and categorizes sounds, such as speech and music, linking auditory regions to the temporal lobe
