chapter 11 sensation and perception vocab

vibration of the basilar membrane

"sorts" or "filters" by frequency so hair cells are activated at different places along the cochlea for different frequencies.

common logarithms

1. numbeer: 10 power of 10: 1 logartihm: 1 2. number: 100 power of 10: 2 logathrim: 2 3. number: 1,000 power of 10: 3 logarithm: 3 4. number: 10,000 power of 10: 4 logartihm: 4

relative amptidues and decibels for environmental sounds

1. sound: barely audible relative amptidue: 1 decibels: 0 2. sound: leaves rustling relative amptidue: 10 decibels: 20 2. sound: quiet residential community relative amptidue: 100 decibels: 40 3. average speaking voice relative amptidue: 1,000 decibles;: 60 4.sound: express subway train relative amptlude: 100,000 decibels: 100 5. sound: propeller plane at takeoff relative amplitude: 1,000,000 decibels: 120 6. sound: jet engine at takeoff (pain threshold) relative amplitude: 10,000,000 decibels: 140

audibiliity curve

A curve that indicates the sound pressure level (SPL) at threshold for frequencies across the audible spectrum.indicates that we can hear sounds between about 20 Hz and 20,000 Hz and that we are most sensitive (the threshold for hearing is lowest) at frequencies between 2,000 and 4,000 Hz, which happens to be the range of frequencies that is most important for understanding speech. at intensties below this we cant hear a tone

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.

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.

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.

tympanic membrane/eardrum

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.

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.

cochalea 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.

the association of frequnecy with place led to the following explanation of the physiology of pitch perception

A pure tone causes a peak of activity at a specific place on the basilar membrane. The neurons connected to that place respond strongly to that frequency, as indicated by the auditory nerve fiber frequency tuning curves in Figure 11.25, and this information is carried up the auditory nerve to the brain. The brain identifies which neurons are responding the most and uses this information to determine the pitch.

fundamental

A pure tone with frequency equal to the fundamental frequency of a complex tone.

oval window

A small, membrane-covered hole in the cochlea that receives vibrations from the stapes.

pure tone

A tone with pressure changes that can be described by a single sine wave.

decibel (dB)

A unit that indicates the pressure of a sound stimulus relative to a reference pressure: where p is the pressure of the tone and is the reference pressure.

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.

outer hair cells

Auditory receptor cells in the inner ear that amplify the response of inner hair cells by amplifying the vibration of the basilar membrane.

inner hair cells

Auditory receptor cells in the inner ear that are primarily responsible for auditory transduction and the perception of pitch.

For high-frequency tones, a nerve fiber may not fire every time the pressure changes because it needs to rest after it fires (see refractory period,

But when the fiber does fire, it fires at the same time in the sound stimulus, as shown in Figures 11.20a and 11.20b. Since many fibers respond to the tone, it is likely that if some "miss" a particular pressure change, other fibers will be firing at that time. Therefore, when we combine the response of many fibers, each of which fires at the peak of the sound wave, the overall firing matches the frequency of the sound stimulus, as shown in Figure 11.20c. What this means is that a sound's repetition rate produces a pattern of nerve firing in which the timing of nerve spikes matches the timing of the repeating sound stimulus.

frequency tuning curve

Curve relating frequency and the threshold intensity for activating an auditory neuron.

Another way to make it difficult to distinguish one instrument from another is to play an instrument's tone backward

Even though this does not affect the tone's harmonic structure, a piano tone played backward sounds more like an organ than a piano because the tone's original decay has become the attack and the attack has become the decay (Berger, 1964; Erickson, 1975). Thus, timbre depends both on the tone's steady-state harmonic structure and on the time course of the attack and decay of the tone's harmonics.

cochlea 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.

phase locking

Firing of auditory neurons in synchrony with the phase of an auditory stimulus.

the auditory system accomplishes three basic tasks during this journey

First, it delivers the sound stimulus to the receptors; second, it transduces this stimulus from pressure changes into electrical signals; and third, it processes these electrical signals so they can indicate qualities of the sound source, such as pitch, loudness, timbre, and location.

at intensies below audibility curve we cnt hear a tone

For example, we wouldn't be able to hear a 30-Hz tone at 40 dB SPL (point A). The upper boundary of the auditory response area is the curve marked "threshold of feeling." Tones with these high amplitudes are the ones we can "feel"; they can become painful and can cause damage to the auditory system. Although humans hear frequencies between about 20 Hz and 20,000 Hz, other animals can hear frequencies outside the range of human hearing

results of speaker

However, although air pressure changes move outward from the speaker, the air molecules at each location move back and forth but stay in about the same place. What is transmitted is the pattern of increases and decreases in pressure that eventually reach the listener's ear. What is actually happening is analogous to the ripples created by a pebble dropped into a still pool of water (Figure 11.1b). As the ripples move outward from the pebble, the water at any particular place moves up and down. The fact that the water does not move forward becomes obvious when you realize that the ripples would cause a toy boat to bob up and down—not to move outward.

but what was responsibble for the narrower vibration? (hallowell davis)

In 1983 Hallowell Davis published a paper titled "An Active Process in Cochlear Mechanics," which began with the attention-getting statement: "We are in the midst of a major breakthrough in auditory physiology." He went on to propose a mechanism that he named the cochlear amplifier, which explained why neural turning curves were narrower than what would be expected based on Békésy's measurements of basilar membrane vibration.

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.

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.

Pitch is most closely related to the physical property of fundamental frequency (the repetition rate of the sound waveform).

Low fundamental frequencies are associated with low pitches (like the sound of a tuba), and high fundamental frequencies are associated with high pitches (like the sound of a piccolo). However, remember that pitch is a psychological, not a physical, property of sound. So pitch can't be measured in a physical way. For example, it isn't correct to say that a sound has a "pitch of 200 Hz." Instead we say that a particular sound has a low pitch or a high pitch, based on how we perceive it.

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.his reduces the transmission of low-frequency sounds and helps to prevent intense low-frequency components from interfering with our perception of high frequencies. In particular, contraction of the muscles may prevent our own vocalizations, and sounds from chewing, from interfering with our perception of speech from other people

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.

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.

frequency spectra

Plots that indicate 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.provide a way of indicating a complex tone's fundamental frequency and harmonics that add up to the tone's complex waveform.

higher harmonic

Pure tones with frequencies that are whole-number (2, 3, 4, etc.) multiples of the fundamental frequency.

harmonic

Pure-tone components of a complex tone that have frequencies that are multiples of the fundamental frequency.

effect of the missing funademental

Removing the fundamental frequency and other lower harmonies from a musical tone does not change the tone's pitch.

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.

what happens when a bird perches on the tree sings?

The action of the bird's vocal organ is transformed into a sound stimulus—pressure changes in the air. These pressure changes trigger a sequence of events that results in a representation of the bird's song within the ears, the sending of neural signals to the brain, and our eventual perception of the bird's song.

The answer to the question "Is there a sound?" is "yes" if we are using the physical definition, because the falling tree causes pressure changes whether or not someone is there to hear them.

The answer to the question is "no" if we are using the perceptual definition, because if no one is in the forest, there will be no experience.

first harmonic

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.

fundament 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.

malleus

The first of the ossicles of the middle ear. Receives vibrations from the tympanic membrane and transmits these vibrations to the incus.

characteristic frequency

The frequency at which a neuron in the auditory system has its lowest threshold.

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.

inner ear

The innermost division of the ear, containing the cochlea and the receptors for hearing.

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.

organ of corti

The major structure of the cochlear partition, containing the basilar membrane, the tectorial membrane, and the receptors for hearing.

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.

sound

The physical stimulus for hearing. The statement "The sound's level was 10 dB" is using sound in this sense. physical definiton: Sound is pressure changes in the air or other medium. perceptual definition: Sound is the experience we have when we hear.

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. at intensities below

loudness

The quality of sound that ranges from soft to loud. For a tone of a particular frequency, loudness usually increases with increasing decibels.

pitch

The quality of sound, ranging from low to high, that is most closely associated with the frequency of a tone

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.

incus

The second of the three ossicles of the middle ear. It transmits vibrations from the malleus to the stapes.

middle ear

The small air-filled space between the auditory canal and the cochlea that contains the ossicles.

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.

condensation speaker's vibrations

The speaker's vibrations affect the surrounding air, as shown in Figure 11.1a. When the diaphragm of the speaker moves out, it pushes the surrounding air molecules together, a process called condensation, which causes a slight increase in the density of molecules near the diaphragm. This increased density results in a local increase in the air pressure above atmospheric pressure. When the speaker diaphragm moves back in, air molecules spread out to fill in the increased space, a process called rarefaction. The decreased density of air molecules caused by rarefaction causes a slight decrease in air pressure. By repeating this process hundreds or thousands of times a second, the speaker creates a pattern of alternating high- and low-pressure regions in the air, as neighboring air molecules affect each other. This pattern of air pressure changes, which travels through air at 340 meters per second

hertz

The unit for designating the frequency of a tone. One Hertz equals one cycle per second.

additionl tones

This means that the second harmonic of our complex tone has a frequency of (Figure 11.5c), the third harmonic has a frequency of (Figure 11.5d), and so on. These additional tones are the higher harmonics of the tone.

ossicles

Three small bones in the middle ear that transmit vibrations from the outer to the inner ear.

But what happens between the audibility curve and the threshold of feeling?

To answer this question, we can pick any frequency and select a point, such as point B, that is just slightly above the audibility curve. Because that point is just above threshold, it will sound very soft. However, as we increase the level by moving up the vertical line, the loudness increases (also see Figure 11.7). Thus, each frequency has a threshold or "baseline"—the decibels at which it can just barely be heard, as indicated by the audibility curve—and loudness increases as we increase the level above this baseline.

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.

why are the ossicles necessary?

We can answer this question by noting that both the outer ear and middle ear are filled with air, but the inner ear contains a watery liquid that is much denser than the air (Figure 11.13). The mismatch between the low density of the air and the high density of this liquid creates a problem: pressure changes in the air are transmitted poorly to the much denser liquid. This mismatch is illustrated by the difficulty you would have hearing people talking to you if you were underwater and they were above the surface.

Later researchers realized that one reason for Békésy's broad vibration patterns was that his measurements were carried out on "dead" cochleas that were isolated from animal and human cadavers.

When modern researchers used more advanced technology that enabled them to measure vibration in live cochleas, they showed that the pattern of vibration for specific frequencies was much narrower than what Békésy had observed

transduction other steps

When the ion channels are open, positively charged potassium ions flow into the cell and an electrical signal results. When the cilia bend in the other direction (Figure 11.18b), the tip links slacken, the ion channels close, and ion flow stops. Thus, the back-and-forth bending of the hair cells causes alternating bursts of electrical signals (when the cilia bend in one direction) and no electrical signals (when the cilia bend in the opposite direction). The electrical signals in the hair cells result in the release of neurotransmitters at the synapse separating the inner hair cells from the auditory nerve fibers and cause these auditory nerve fibers to fire.

periodic sounds

a sound stimulus in which the patternn of pressure changes repeats. ex musical insruments

periodic tone

a tone in which the waveform repeats

we will focus on inner hair cells

because these are the main receptors responsible for generating signals that are sent to the cortex in auditory nerve fibers.

If vibrations had to pass directly from the air in the middle ear to the liquid in the inner ear, less than 1 percent of the vibrations would be transmitted (Durrant & Lovrinic, 1977). The ossicles help solve this problem in two ways:

by concentrating the vibration of the large tympanic membrane onto the much smaller stapes, which increases the pressure by a factor of about 20 (Figure 11.14a); and (2) by being hinged to create a lever action—an effect similar to what happens when a fulcrum is placed under a board, so that pushing down on the long end of the board makes it possible to lift a heavy weight on the short end

bending of the cilia

follows the increases and decreases of the pressure of a pure tone sound stimulus. When the pressure increases, the cilia bend to the right, the hair cell is activated, and attached auditory nerve fibers will tend to fire. When the pressure decreases, the cilia bend to the left, and no firing occurs. This means that auditory nerve fibers fire in synchrony with the rising and falling pressure of the pure tone.

transduction for hearing

invovles a sequence of events that creates ion flow. first the cilia of the hair cells bend in one direction

the first step in understanding the perceptual process for hearing

is identifying the distal stimulus

the up and down motin of the bailar membrane has two results

it sets the organ of Corti into an up-and-down vibration, and (2) it causes the tectorial membrane to move back and forth, as shown by the red arrow. These two motions mean that the tectorial membrane slides back and forward just above the hair cells. The movement of the tectorial membrane causes the cilia of the outer hair cells that are embedded in the membrane to bend. The cilia of the other outer hair cells and the inner hair cells also bend, but in response to pressure waves in the liquid surrounding the cilia

Although a repeating sound wave is composed of harmonics with frequencies that are whole-number multiples of the fundamental frequency

not all the harmoincs need to be present for the repetion rate to stay the same

sound stimulus

occurs when the movements or vibrations of an object cause pressure changes in air, water, or any other elastic medium that can transmit vibrations

we can appreciate the efect of the ossicles by noting that in

patients whose ossicles have been damaged beyond surgical repair, it is necessary to increase the sound pressure by a factor of 10 to 50 to achieve the same hearing as when the ossicles were functioning

The idea that pitch is associated with the musical scale is reflected in another definition of pitch

pitch is that aspect of auditory sensation whose variation is associated with musical melodies

humans can perceive frequencies

ranging from about 20hz to abut 20,000 hz

cochalea ampifler greatly

shaprens the tuning of each place along the cochlea

ss stevens finding of relationship between level in decibels (physical) and loudness (perceptual) using the magnitude estimation procedure

shows the relationship between decibels and loudness for a 1,000-Hz pure tone. In this experiment, loudness was judged relative to a 40-dB SPL tone, which was assigned a value of 1. Thus, a pure tone that sounds 10 times louder than the 40-dB SPL tone would be judged to have a loudness of 10. The dashed lines indicate that increasing the sound level by 10 dB (from 40 to 50) almost doubles the sound's loudness.

aperiodic sounds

sound waves that do not repeat ex door slamming shut, people tlaking, static on radio not tuend to a station

davis propsoed

that the cochlear amplifier was an active mechanical process that took place in the outer hair cells. We can appreciate what this active mechanical process is by describing how the outer hair cells respond to and influence the vibration of the basilar membrane

bekesy most importatn finding

that the place that vibrates the most depends on the freuqency of the tone

pinnae

the aprt of the ear that is visible on the outside of the head

attack

the buildup of sound energy that occurs at the beginning of a tone

auditory canal

the canal through which air vibrations travel from the environment to the tympanic membrane. tublikerecess bout 3cm long in adults. protects the delicate structures of the middle ear from the hazards of the outside world. enhance the intensties of some sounds by menas of the physical principel of resonance

decay

the decrease in the sound signal that occurs at the end of a tone

base

the end of the cochlea nearest the middle ear

apex

the end of the cohclea frather from the middle ear

tone height

the increase in pitch that occurs as frequency is increased

charles eambes film

the increase in size from 1 to 1,000 million million that occurs as Charles Eames's spaceship zooms out to the edge of the Milky Way is converted into a more manageable scale of 14 log units. The range of sound pressures encountered in the environment, while not as astronomical as the range in Eames's film, ranges from 1 to 10,000,000, which in powers of 10 is a range of 7 log units.

the cochlea's filtering action is reflected by the following three characteristics of tuning curves

the neurons respond best to one frequency; (2) each frequency is associated with nerve fibers located at a specific place along the basilar membrane, with fibers originating near the base of the cochlea having high characteristic frequencies and those originating near the apex having low characteristic frequencies; (3) the curves become wider at higher frequencies.

tone chroma

the peceptual similarity of notes separate by one or more octaves

outer ear

the pinna and the auditory canal

soundn level

the pressure of a sound stimulus, expressed in decibels

Measurements of the sound pressures inside the ear indicate that

the resonance that occurs in the auditory canal has a slight amplifying effect that increases the sound pressure level of frequencies between about 1,000 and 5,000 Hz, which, as we can see from the audibility curve in Figure 11.8, covers the most sensitive range of human hearing.

one way to specify a sound's amplitude would be

to indicate the difference in pressure between the high and low peaks of the sound wave. larger amptidue is associated with the perception of greater loudness

the major purpose of outer hair cells is

to influence the way the basilar membrane vibrates, and they accomplish this by changing length (Ashmore, 2008; Ashmore et al., 2010). While ion flow in inner hair cells causes an electrical response in auditory nerve fibers, ion flow in outer hair cells causes mechanical changes inside the cell that causes the cell to expand and contract, as shown in Figure 11.26. The outer hair cells become elongated when the cilia bend in one direction and contract when they bend in the other direction. This mechanical response of elongation and contraction pushes and pulls on the basilar membrane, which increases the motion of the basilar membrane and sharpens its response to specific frequencies.