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Additive Synthesis
In hearing, the process of building a complex tone by starting with the fundamental frequency and adding pure tone harmonics. TERM 2
Amplitude
DEFINITION 2 In the case of a repeating sound wave, such as the sine wave of a pure tone, this represents the pressure difference between atmospheric pressure and the maximum pressure of the wave. TERM 3
Apex of the Cochlea
DEFINITION 3 The end of the basilar membrane farthest from the middle ear. TERM 4
Attack
DEFINITION 4 The buildup of sound at the beginning of a tone. TERM 5
Audibility Curve
DEFINITION 5 A curve that indicates the sound pressure level (SPL) at threshold for frequencies across the audible spectrum.
Auditory Canal
The canal through which air vibrations travel from the environment to the tympanic membrane. TERM 7
Auditory Masking
DEFINITION 7 Occurs when presentation of one sound decreases a listeners ability to hear another sound. TERM 8
Auditory Receiving Area
DEFINITION 8 The area of the cortex, located in the temporal lobe, that is the primary receiving area for hearing. TERM 9
Auditory Response Area
DEFINITION 9 The psychophysically measured area that defines the frequencies and sound pressure levels over which hearing functions. This area extends between the audibility curve and the curve for the threshold of feeling. TERM 10
Base of the Cochlea
DEFINITION 10 The part of the basilar membrane nearest the middle ear.
Cochlear Amplifier
How movement of the outer hair cells in response to sound increases basilar membrane vibration and therefore amplies the response of the inner hair cells. TERM 17
Cochlear Nucleus
DEFINITION 17 The nucleus where nerve fibers from the cochlea first synapse. TERM 18
Cochlear Implant
DEFINITION 18 A device in which electrodes are inserted into the cochlea to create hearing by electrically stimulating the auditory nerve bers. This device is used to restore hearing in people who have lost their hearing because of damaged hair cells. TERM 19
Cochlear Partition
DEFINITION 19 A partition in the cochlea, extending almost its full length, that separates the scala tympani and the scala vestibuli. The organ of Corti, which contains the hair cells, is part of the cochlear partition. TERM 20
Conductive Hearing Loss
DEFINITION 20 Hearing loss that occurs when the vibrations of a sound stimulus are not conducted normally from the outer ear into the cochlea.
Core Area
The area in the temporal lobe that includes the primary auditory cortex (A1) and some nearby areas. Signals from the core area are transmitted to the belt area of the auditory cortex. TERM 22
Decay
DEFINITION 22 The decrease in the sound signal that occurs at the end of a tone. TERM 23
Decibel
DEFINITION 23 A unit that indicates the presence of a tone relative to a reference pressure: dB 20 log (p/po) where p is the pressure of the tone and po is the reference pressure. TERM 24
Eardrum
DEFINITION 24 Another term for the tympanic membrane, the membrane located at the end of the auditory canal that vibrates in response to sound. TERM 25
Effect of the Missing Fundamental
DEFINITION 25 Removing the funda mental frequency and other lower harmonies from a musical tone does not change the tones pitch.
Frequency Tuning Curve
Curve relating frequency and the threshold intensity for activating an auditory neuron. TERM 32
Fundamental Frequency
DEFINITION 32 The first harmonic of a complex tone; usually the lowest frequency in the frequency spectrum of a complex tone. The tones other components, called higher harmonics, have frequencies that are multiples of the fundamental frequency. TERM 33
Hair Cell
DEFINITION 33 Neuron in the cochlea that contains small hairs, or cilia, that are displaced by vibration of the basilar membrane and fluids inside the inner ear. There are two kinds of hair cells: inner and outer. TERM 34
Harmonics
DEFINITION 34 Fourier components of a complex tone with frequencies that are multiples of the fundamental frequency. TERM 35
Hertz (Hz)
DEFINITION 35 The unit for designating the frequency of a tone. One Hertz equals one cycle per second.
Hierarchal Processing
Processing signals through a sequence of areas. This occurs in the visual system as signals are transmitted from the LGN to the primary visual receiving area and then to higher areas. It occurs in the auditory system as signals are transmitted from the core to the belt to the parabelt regions of the cortex. TERM 37
Incus
DEFINITION 37 The second of the three ossicles of the middle ear. It trans- mits vibrations from the malleus to the stapes. TERM 38
Inferior Colliculus
DEFINITION 38 A nucleus in the hearing system along the pathway from the cochlea to the auditory cortex. The inferior colliculus receives inputs from the superior olivary nucleus. TERM 39
Inner
Ear
DEFINITION 39 The innermost division of the ear, containing the cochlea and the receptors for hearing. TERM 40
Inner Hair Cells
DEFINITION 40 Auditory receptor cell in the inner ear that is primarily responsible for auditory transduction and the per- ception of pitch.
Middle-ear Muscles
Muscles attached to the ossicles in the middle ear. The smallest skeletal muscles in the body, they contract in response to very intense sounds and dampen the vibration of the ossicles. TERM 47
Noise-induced Hearing Loss
DEFINITION 47 A form of sensorineural hearing loss that occurs when loud noises cause degeneration of the hair cells. TERM 48
Octave
DEFINITION 48 Tones that have frequencies that are binary multiples of each other (2, 4, etc.). For example, an 800-Hz tone is one octave above a 400-Hz tone. TERM 49
Organ of Corti
DEFINITION 49 The major structure of the cochlear partition, containing the basilar membrane, the tectorial membrane, and the receptors for hearing. TERM 50
Ossicles
DEFINITION 50 Three small bones in the middle ear that transmit vibrations from the outer to the inner ear.
Outer
Ear
The pinna and the external auditory meatus. TERM 52
Outer Hair Cells
DEFINITION 52 Auditory receptor cells in the inner ear that amplify the response of the inner hair cells. TERM 53
Oval Window
DEFINITION 53 A small, membrane-covered hole in the cochlea that receives vibrations from the stapes. TERM 54
Parabelt Area
DEFINITION 54 Auditory area in the temporal lobe that receives signals from the belt area. TERM 55
Periodicity Pitch
DEFINITION 55 The constancy of a complex tones pitch when the fundamental frequency and other lower harmonics are eliminated.
Presbycusis
A form of sensorineural hearing loss that occurs as a function of age and is usually associated with a decrease in the ability to hear high frequencies. Since this loss also appears to be related to exposure to environmental sounds, it is also called sociocusis. TERM 62
Pure Tone
DEFINITION 62 A tone with pressure changes that can be described by a single sine wave. TERM 63
Range of Hearing
DEFINITION 63 The specific range of frequencies within which we hear sound. TERM 64
Resonance
DEFINITION 64 A mechanism that enhances the intensity of certain frequencies because of the reflection of sound waves in a closed tube. Resonance in the auditory canal enhances frequencies between about 2,000 and 5,000 Hz. TERM 65
Resonant Frequency
DEFINITION 65 The frequency that is most strongly enhanced by resonance. The resonance frequency of a closed tube is determined by the length of the tube.
Sensorineural Hearing Loss
Hearing loss caused by damage within the inner ear. TERM 67
Sound Level
DEFINITION 67 The pressure of a sound stimulus, expressed in decibels. TERM 68
Sound Pressure Level (SPL)
DEFINITION 68 A designation used to indicate that the reference pressure used for calculating a tones decibel rating is set at 20 micropascals, near the threshold in the most sensitive frequency range for hearing. TERM 69
Stapes
DEFINITION 69 The last of the three ossicles in the middle ear. It receives vibrations from the incus and transmits these vibrations to the oval window of the inner ear. TERM 70
Sound Wave
DEFINITION 70 Pattern of pressure changes in a medium. Most of the sounds we hear are due to pressure changes in the air, although sound can be transmitted through water and solids as well
Tone Chroma
The perceptual similarity of notes separated by one or more octaves. TERM 77
Tone Height
DEFINITION 77 The increase in pitch that occurs as frequency is increased. TERM 78
Tonotopic Map
DEFINITION 78 An ordered map of frequencies created by the responding of neurons within structures in the auditory system. There is a tonotopic map of neurons along the length of the cochlea, with neurons at the apex responding best to low frequencies and neurons at the base responding best to high frequencies. TERM 79
Traveling Wave
DEFINITION 79 In the auditory system, vibration of the basilar membrane in which the peak of the vibration travels from the base of the membrane to its apex.
