Chapter 9: Psychoacoustics and Auditory Physiology Flashcards
(22 cards)
Sound Pressure Waves
-Produced by any vibrating stimulus
- Compression of molecules through any media is audible
-Speed of pressure waves depends on medium
Sine waves
-Characterize sound waves
-Single sine waves are pure tones
-Most sounds are complex tones, consisting of many frequencies
Amplitude
Intensity (perceived loudness)
-Decibels
Frequency
Related to perceived pitch (Hertz)
Audible Range
-Frequency of 20-20,000 Hz
-Most sensitive from 1000-4000Hz
-Intensity -5dB-140dB
-Above 114dB is harmful
Dynes
Pressure ratios are a measure of sound pressure changes
Complex tones
Created through additive synthesis
-Fundamental frequency is the lowest
-Harmonics are multiples of fundamental
-NonHarmonics are incongruent with fundamental
Fourier Analysis
Used to identify the individual frequencies present in a complex tone
Harmonic Spectrum
-All frequencies in a complex tone
Jobs of Auditory System
- Gather sound waves
- Transduce sound waves to neural signals
- Process/interpret neural signals
Auditory System Parts
- Outer Ear
- Middle Ear
- Inner Ear
Outer Ear Structures and Job
Main Structures:
-Pinna
-Auditory Canal
-Tympanic Membrane (Eardrum)
-Sound waves are funneled from environment by the pinna
-Length and shape of the ear canal enhances certain frequencies
Middle Ear Structures and Job
-Converts air pressure waves into liquid pressure waves within the inner ear
-Contains the ossicles:
-Malleus -> Incus -> Stapes
-Connected via small muscles
–Tensor Tympani + Stapedius
-Ends at the oval window
Inner Ear
-Small Delicate Structure where pressure waves are transduced into neural signals
-Functionally analogous to the retina
-Main structure is the cochlea which contains three fluid-filled champers
–Vestibular Canal
–Middle Canal
–Tympanic Canal
-These Chambers are separated by membranes
–Reissner’s Membrane
–Basilar Membrane
-Organ of Corti lies on the Basilar Membrane
–Movement of tectorial membrane stimulates hair cells
-Stereocilia/Hair cells
–Dendritic ends of auditory nerve which transduce movement into neural impulses
–Inner Hair cells and Outer hair cells
-Vibrations displace the tectorial membrane which bends hair cells and causes release of neurotransmitters
Tonotopic layout
Place Theory of Hearing
-Each section of the cochlea is tuned to -specific frequencies
-Frequencies are coded at locations along Organ of Corti
-Auditory Nerve fibers along Organ Corti are tuned to different frequencies
-Vibrating motion produces traveling wave along cochlea that generates a place code
-Place code is the location with the greatest displacement
Auditory Processing in the Cortex
-Contralateral Processes
-Auditory Nerve is Cranial Nerve V3
–Cochlear nuclei processes ipsilateral ear
-Superior olivary nucleus process the contralateral ear
-Medial Geniculate Nucleus
Primary Auditory Cortex (A1)
-Two processing streams
-Dorsal(Where) stream
-Ventral(What) Stream
Psychoacoustics
-Branch of psychophysics
-Studies relationship between physical sound and perception of sound
Audiometry
Measuring one’s auditory sensitivity
Hearing Impairments
-Difficulty hearing less intense frequencies
-Due to injury along auditory pathway or buildup of ear wax
Tinnitus
Hearing of consistent noise
Conductive Hearing Loss
-Involves middle ear bones, preventing sound from reaching the inner ear
-Otitis Media is caused by ear infections
-Otosclerosis is due to abnormal bone growth
Sensorineural Hearing Loss
-More common and more serious
-Results from defects and damage to inner ear or auditory nerve
-Exposure to intense sounds
