L5-L7 Flashcards
How is sound produced?
physical vibration of objects (a purely mechanical phenomena)
Compression vs rarefaction
air molecules bunch together (high air pressure); air molecules spread apart (low air pressure)
Frequency
rate of fluctuation of sound pressure measured in cycles/second or Hertz (Hz)
Phase
part of the cycle the sound pressure wave has reached at a given point in time; measured in degrees until 360°; often used to compare the timing of 2 sound waves
Amplitude
maximum pressure change of wave above normal atmospheric pressure that determines sound intensity
Pure tones
represented by single sine wave and produced by a tuning fork, wherein sound pressure level corresponds to loudness and frequency corresponds to pitch
Fourier’s theorem
most sounds are complex and can be described as a set of sine waves
Fourier analysis
mathematical procedure for separating a complex pattern into component sine waves that vary over time (hearing) and space (vision)
Fundamental frequency
lowest sine-wave frequency in a complex sound that usually determines perceived pitch
Harmonics
higher frequency sine-wave components; integer multiples of fundamental frequency
What do differences in frequency and amplitude in harmonics determine?
the psychological attribute of quality or timbre (i.e. explains why instruments sound different when playing the same note)
Function of the shape of the pinna
helps with sound localization
Function of the length and shape of the ear canal
enhances sounds 2000-6000 Hz (range of frequency where humans are most sensitive)
Function of the middle ear
impedance matching and protecting the inner ear from potentially harmful loud sounds through acoustic reflex
Impedance matching
middle ear amplifies sound energy to reduce loss due reflection at the oval window (air/fluid boundary)
Acoustic reflex
tensor tympani and stapedius muscles contract to reduce the magnitude of the auditory signal transmitted to the inner ear, in response to prolonged sounds
Function of the eustachian tube
equalizes air pressure between the middle and outer ear
3 canals in the inner ear
vestibular canal (scala vestibuli), middle canal (cochlear duct or scala media), tympanic canal (scala tympani)
What do the vestibular and tympanic canals contain?
fluid called perilymph
What does the middle canal contain?
fluid called endolymph and organ of corti that contains auditory receptors (where mechanical energy is transduced into neural signals)
Function of the tunnel of corti
locating 2 different hair cells: 1 row of 3500 inner hair cells on one side and 3 rows of ~10500 outer hair cells on the other
Location of inner hair cells vs outer hair cells in the cochlea
single row of stereocilia that rests against the tectorial membrane (gelatinous roof of the organ of corti); V-shape arrangement of stereocilia with the tallest embedded in the tectorial membrane
Function of inner hair cells
act as sensory receptors that convey information about sound to the brain
have no axons but release neurotransmitters at the synapse with afferent fibers
Function of outer hair cells
modulate sensitivity and frequency-tuning of cochlear partition