Auditory System Flashcards
Hertz (Hz)
Unit measurement of frequency (cycles per second)
One Hz is one cycle per second
Frequency
Cycles per second
Frequency is ____________ to wavelength
Inversely related
Shorter wavelength - higher frequency
Human range
20 to 20 K Hz
Intensity
Amplitude, measured in bels
Bels are too broad to capture sensitivity so we use decibels (tenth of a bel)
Sounds above 140 db tend to be painful
Perceptual concept of intensity: loudness
Subjective dimensions of sound:
Loudness, pitch, timbre
Loudness
Subjective experience of magnitude or intensity
Pitch
Subjective experience of perceived frequency
Timbre
Sound quality
Created by the specific combination of frequencies that make up the sound wave
Middle to inner ear
Malleus, incus, stapes
Stapes rests on oval window (entrance to inner ear)
Inner ear
Organ of Corti rests on basilar membrane in cochlea
Organ of Corti is composed of hair cells (auditory sensorireceptors)
Auditory nerve projection sites
Superior olive, inferior colliculus, MGN (medial geniculate nucleus in thalamus), then to auditory cortex in temporal lobe and association areas
Helmholtz’s Place-Resonance Theory
Each pitch causes different place on basilar membrane to vibrate
Operative for tones above 4000 Hz
Frequency Theory
Rate of vibration of whole membrane is equal to frequency of stimulus (determines perception of pitch)
Does not apply, however, to sounds above 1000 Hz
Weber and Bray modified frequency theory by proposing volley principle: states that high rates of neural firing can be maintained if nerve fibers work together
Von Békésy’s Traveling Wave
Found that the movement of the basilar membrane is maximal at a different place along the basilar membrane for each different frequency (although the whole membrane vibrates for any given stimulus)
High frequencies vibrate the membrane near the base; low frequencies vibrate maximally vibrate near the apex
