Chapter 11 Flashcards
Acoustic prism
The way the cochlea separates frequencies entering the ear to create activity at different places along the basilar membrane.
Amplitude
In the case of a repeating sound wave, such as the sine wave of a pure tone, amplitude represents the pressure difference between atmospheric pressure and the maximum pressure of the wave.
Apex of the cochlea
The end of the cochlea farthest from the middle ear.
Attack
The buildup of sound energy that occurs at the beginning of a tone.
Audibility curve
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.
Auditory response area
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.
Base of the cochlea
The part of the cochlea nearest the middle ear.
Basilar membrane
A membrane that stretches the length of the cochlea and controls the vibration of the cochlear partition.
Characteristic frequency
The frequency at which a neuron in the auditory system has its lowest threshold.
Cilia
Fine hairs that protrude from the inner and outer hair cells of the auditory system. Bending the cilia of the inner hair cells leads to transduction.
Cochlea
The snail-shaped, liquid-filled structure that contains the structures of the inner ear, the most important of which are the basilar membrane, the tectorial membrane, and the hair cells.
Cochlear amplifier
Expansion and contraction of the outer hair cells in response to sound sharpens the movement of the basilar membrane to specific frequencies. This amplifying effect plays an important role in determining the frequency selectivity of auditory nerve fibers.
Cochlear implant
A device in which electrodes are inserted into the cochlea to create hearing by electrically stimulating the auditory nerve fibers. This device is used to restore hearing in people who have lost their hearing because of damaged hair cells.
Cochlear partition
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.
Decay
The decrease in the sound signal that occurs at the end of a tone.
Decibel (dB)
A unit that indicates the pressure of a sound stimulus relative to a reference pressure: dB=20 log (p/po) where p is the pressure of the tone and po is the reference pressure.
Eardrum
Another term for the tympanic membrane, the membrane located at the end of the auditory canal that vibrates in response to pressure changes. This vibration is transmitted to the bones of the middle ear.
Effect of the missing fundamental
Removing the fundamental frequency and other lower harmonies from a musical tone does not change the tone’s pitch. See also periodicity pitch.
Equal loudness curve
A curve that indicates the sound pressure levels that result in a perception of the same loudness at frequencies across the audible spectrum.
First harmonic
A pure tone with frequency equal to the fundamental frequency of a complex tone. See also fundamental frequency.
Frequency
The number of times per second that pressure changes of a sound stimulus repeat. Frequency is measured in Hertz, where 1 Hertz is one cycle per second.
Frequency spectrum
A plot that indicates the amplitudes of the various harmonics that make up a complex tone. Each harmonic is indicated by a line that is positioned along the frequency axis, with the height of the line indicating the amplitude of the harmonic.
Frequency tuning curve
Curve relating frequency and the threshold intensity for activating an auditory neuron.
Fundamental
A pure tone with frequency equal to the fundamental frequency of a complex tone. See also fundamental frequency.
Fundamental frequency
The fi rst harmonic of a complex tone; usually the lowest frequency in the frequency spectrum of a complex tone. The tone’s other components, called higher harmonics, have frequencies that are multiples of the fundamental frequency.
Hair cell
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.
Harmonics
Pure-tone components of a complex tone that have frequencies that are multiples of the fundamental frequency.
Hertz (Hz)
The unit for designating the frequency of a tone. One Hertz equals one cycle per second.
Higher harmonics
Pure tones with frequencies that are whole-number (2, 3, 4, etc.) multiples of the fundamental frequency. See also fundamental; fundamental frequency; harmonics.
Incus
The second of the three ossicles of the middle ear. It transmits vibrations from the malleus to the stapes. (anvil)
Inner ear
The innermost division of the ear, containing the cochlea and the receptors for hearing.
Inner hair cell
Auditory receptor cell in the inner ear that is primarily responsible for auditory transduction and the perception of pitch.
Leisure noise
Noise associated with leisure activities such as listening to music, hunting, and woodworking. Exposure to high levels of leisure noise for extended periods can cause hearing loss.
Level
Short for sound pressure level or sound level. Indicates the decibels or sound pressure of a sound stimulus.
Loudness
The quality of sound that ranges from soft to loud. For a tone of a particular frequency, loudness usually increases with increasing decibels.
Malleus
The first of the ossicles of the middle ear. Receives vibrations from the tympanic membrane and transmits these vibrations to the incus. (hammer)
Middle ear
The small air-filled space between the auditory canal and the cochlea that contains the ossicles.
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.
Noise-induced hearing loss
A form of sensorineural hearing loss that occurs when loud noises cause degeneration of the hair cells.
Octave
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.
Organ of Corti
The major structure of the cochlear partition, containing the basilar membrane, the tectorial membrane, and the receptors for hearing.
Ossicles
Three small bones in the middle ear that transmit vibrations from the outer to the inner ear.
Outer ear
The pinna and the auditory canal.
Outer hair cell
Auditory receptor cells in the inner ear that amplify the response of inner hair cells by amplifying the vibration of the basilar membrane.
Oval window
A small, membrane-covered hole in the cochlea that receives vibrations from the stapes.
Periodic tone
A tone in which the waveform repeats.
Periodicity pitch
The constancy of a complex tone’s pitch when the fundamental frequency and other lower harmonics are eliminated. See also effect of the missing fundamental.
Phase locking
Firing of auditory neurons in synchrony with the phase of an auditory stimulus.
Pinna
The part of the ear that is visible on the outside of the head.
Pitch
The quality of sound, ranging from low to high, that is most closely associated with the frequency of a tone.
Pitch neurons
Neurons that respond to stimuli associated with a specific pitch. These neurons fire to the pitch of a complex tone even if the first harmonic or other harmonics of the tone are not present.
Place theory of hearing
The proposal that the frequency of a sound is indicated by the place along the organ of Corti at which nerve firing is highest. Modern place theory is based on Békésy’s traveling wave theory of hearing.
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.
Pure tone
A tone with pressure changes that can be described by a single sine wave.
Resonance
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.
Resonant frequency
The frequency that is most strongly enhanced by resonance. The resonance frequency of a closed tube is determined by the length of the tube.
Sound (perceptual)
The perceptual experience of hearing. The statement “I hear a sound” is using sound in that sense.
Sound (physical)
The physical stimulus for hearing. The statement “The sound’s level was 10 dB” is using sound in that sense.
Sound level
The pressure of a sound stimulus, expressed in decibels. See also sound pressure level (SPL).
Sound pressure level (SPL)
A designation used to indicate that the reference pressure used for calculating a tone’s decibel rating is set at 20 micropascals, near the threshold in the most sensitive frequency range for hearing.
Sound wave
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.
Stapes
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. (stirrup)
Tectorial membrane
A membrane that stretches the length of the cochlea and is located directly over the hair cells. Vibrations of the cochlear partition cause the tectorial membrane to bend the hair cells by rubbing against them.
Temporal coding
The connection between the frequency of a sound stimulus and the timing of the auditory nerve fiber firing.
Timbre
The quality that distinguishes between two tones that sound different even though they have the same loudness, pitch, and duration. Differences in timbre are illustrated by the sounds made by different musical instruments.
Tip links
Structures at the tops of the cilia of auditory hair cells, which stretch or slacken as the cilia move, causing ion channels to open or close.
Tone chroma
The perceptual similarity of notes separated by one or more octaves.
Tone height
The increase in pitch that occurs as frequency is increased.
Tonotopic map
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.
Traveling wave
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.
Tympanic membrane
A membrane at the end of the auditory canal that vibrates in response to vibrations of the air and transmits these vibrations to the ossicles in the middle ear.
