Topic 11: Hearing Flashcards
Sound
the perceptual experience of hearing
the statement “I hear a sound” is using sound in this sense
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
Pure Tone
a tone with pressure changes that can be described by a single sine wave
Frequency
the number of times per second that pressure changes of a sound stimulus repeat
is measured in Hertz, where 1 Hertz is one cycle per second
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
Hertz (Hz)
the unit for designating the frequency of a tone
1 Hertz equals one cycle per second
Decibel (dB)
a unit that indicates the pressure of a sound stimulus relative to a reference pressure: dB = 20log(p/po), where p is the pressure of the tone and po is the reference pressure
Sound Pressure Level
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
Level
short for sound pressure level or sound level
indicates the decibels or sound pressure of a sound stimulus
Sound Level
the pressure of a sound stimulus, expressed in decibels
Periodic Waveform
for the stimulus for hearing, a pattern of repeating pressure changes
Fundamental Frequency
the first 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
Harmonic
pure-tone components of a complex tone that have frequencies that are multiples of the fundamental frequency
Fundamental
a pure tone with frequency equal to the fundamental frequency of a complex tone
Higher Harmonics
pure tones with frequencies that are whole number (2, 3, 4, etc.) multiples of the fundamental frequencies
Frequency Spectra
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
Loudness
the quality of sound that ranges from soft to loud
for a tone of a particular frequency, loudness usually increases with increasing decibels
Audibility Curve
a curve that indicates the sound pressure level (SPL) at threshold for frequencies across the audible system
Auditory Response Area
the psychophysically measured area that defines the frequencies and sound pressure levels over which hearing frequencies and sound pressure levels over which hearing functions
this area extends between the audibility curve and the curve for the threshold of feeling
Equal Loudness Curves
a curve that indicates the sound pressure levels that result in a perception of the same loudness at frequencies across the audible spectrum
Pitch
the quality of sound, ranging from low to high, that is most closely associated with the frequency of a tone
Tone Height
the increase in pitch that occurs as frequency is increased
Tone Chroma
the perceptual similarity of notes separated by one or more octaves
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
Effect of the Missing Fundamental
removing the fundamental frequency and other lower harmonies from a musical tone do not change the tone’s pitch
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 make by different musical instruments
Attack
the buildup of sound energy that occurs at the beginning of a tone
Decay
the decrease in the sound signal that occurs at the end of a tone
Periodic Sounds
a sound stimulus in which the pattern of pressure changes repeats
Aperiodic Sounds
sound waves that do not repeat
Outer Ear
the pinna and the auditory canal
Pinnae
the part of the ear that is visible on the outside of the head
Auditory Canal
the canal through which air vibrations travel from the environment to the tympanic membrane
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
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
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
Middle Ear
the small air-filled space between the auditory canal and the cochlea that contains the ossicles
Ossicles
three small bones in the middle ear that transmit vibrations from the outer to the inner ear
Malleus
the first of the ossicles of the middle ear
receives vibrations from the tympanic membrane and transmits these vibrations to the incus
Incus
the second of the ossicles of the middle ear
it transmits vibrations from the malleus to the stapes
Stapes
the last of the three ossicles of the middle ear
it receives vibrations from the incus and transmits these vibrations to the oval window of the inner ear
Oval Window
a small, membrane-covered hole in the cochlea that receives vibrations from the stapes
Middle Ear Muscles
muscles attached to the ossicles in the middle ear
the smallest skeletal muscles in the body, the contract in response to very intense sounds and dampen the vibration of the ossicles
Inner Ear
the innermost division of the ear, containing the cochlea and the receptors for hearing
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 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
Organ of Corti
the major structure of the cochlear partition, containing the basilar membrane, the tectorial membrane, and the receptors for hearing
Hair Cells
neurons in the cochlea that contain 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
Basilar Membrane
a membrane that stretches the length of the cochlea and controls the vibration of the cochlear partition
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
Stereocilia
thin processes that protrude from the tops of the hair cells in the cochlea that bend in response to pressure changes
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