Sensation & Perception Final

What does the McGurk effect suggest about speech perception?

What we hear is affected by what we see.

phonemic restoration effect

When a phoneme is missing in speech that we hear, the brain fills it in based on our knowledge of the language being spoken

typanic membrane

seals off auditory canal and vibrates in response to sound waves, then transmits vibrations to middle ear

phonetic boundary

the voice onset time between one speech category changing into another

resonance

amplifies sounds between 2000 and 5000 Hz

incus

anvil; transmits vibrations from the malleus to the stapes

ossicles

bones called malleus, incus, and stapes

What information does a speech spectrogram reveal?

changes intensities

voice onset time

delay between beginning of sound and vocal cord vibration

interaural intensity difference

difference in intensity of sound reaching each ear for high frequencies; sensitive to high frequencies

place theory

different sound frequencies disturb different regions of the basilar membrane

frequency

the number of cycles per second

volley principle

frequency indicated by pattern of activity across group of neurons. Neurons fire in staggered fashion

auditory canal

gathers sound waves from the pinna onto the tympanic membrane; serves for protection, temperature control, resonance

cochlear nucles

gets input from cochlea from the same side of the head

malleus

hammer; vibrates in response to tympanic membrane

harmonics

higher frequencies that are multiples of the fundamental frequency; determines timbre

azimuth

horizontal; based on differences between information reaching each ear

basilar membrane

wider near apex than the base; stiffer near base; movement determined by frequency of sound

binaural

you need two ears

cochlea

A structure filled with fluid that contains the inner ear structures, the most important of which are the basilar membrane, the tectorial membrane, and the hair cells.

pitch

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

oval window

A membrane-covered opening in between the stapes and the cochlea. Causes cochlear fluid to move when stapes moves.

decibel

A physical unit used to measure sound amplitude

spectral cues

notches and peaks

How does transduction into neural impulses occur in the ear?

(?) movement of basilar membrane cause hair cell ciliae to bend; bend in one direction: depolarize and release NT; bend in other direction: hyperpolarize- stop NT release.

Trace the changes in the ear that follow the entrance of a sound wave into the ear (from the pinna through the hair cells).

1. Sound waves enter auditory canal 2. Tympanic membrane vibrates rate determined by wave frequency. 3. Ossicle transmit vibration to oval window. 4. Pressure on oval window cause cochlear fluid in scala vestibuli to move. 5. Fluid movement continues through heloicotoma into scala tympani. 6. Basilar membrane moves when basilar membrane moves. 7. Organ of Corti moves when basilar membrane moves. 8. Ciliae in hair cells bend in response to movement. 9. Bending of hair cells produces neural signals.

Describe an experiment that illustrates the phonemic restoration effect.

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How is the acoustic signal produced and what determines its properties?

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McGurk effect

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What do categorical perception experiments demonstrate?

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What is the variability in speech perception? What is one way that human listeners might solve the variability problem?

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categorical perception

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What are interaural time and intensity differences, and how do they signal the location of a sound source?

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auditory scene analysis

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direct sound

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indirect sound

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traveling wave

A traveling wave is a wave that increases in amplitude as it moves, until it reaches its peak size; For high frequency sounds, the wave travels only a very short distance before it reaches its peak (closer to base). For low frequency sounds, the wave travels a long way down the basilar membrane before reaching its peak (closer to apex).

eustachian tube

A tube connecting the middle ear to the top of the throat; opens to equalize pressure between outer ear and middle ear

Describe two ways in which the ossicles help overcome impedance mismatch.

Act as lever: increase force; focus vibrations of large surface onto small surface- tympanic membrane & oval window.

impedance mismatch

Air has low impedance and fluid has high impedance. More energy is needed to create wave in the fluid. As a result, the amount of energy in a sound wave isn't enough on its own to create a wave just before the oval window. This is overcame by the ossicles amplifying the amount of pressure placed on the oval window and producing a wave in the cochlea.

Why do high frequency sounds produce larger interaural intensity differences than low frequency sounds?

Because it is easier to interfere with higher frequency sounds -- the head only creates an acoustic shadow for those sounds. Low-frequency sounds pass by the head without being effected much.

Trace the brain structures which process the auditory signal after it leaves the cochlea.

Cochlear nucleus, superior olivary nucleus, inferior colliculus, medial geniculate, auditory cortex

What are compression and rarefaction?

Compression- pushing on air molecules closer, creates a higher pressure region; rarefaction- pulls the molecules apart, creates a low pressure region.

How can place and frequency theory be reconciled?

Each theory applies to different frequencies. Frequency theory applies to low frequencies and the place theory applies to higher frequencies.

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.

How does a sound's frequency convey information about distance?

For a moving source, the Doppler Shift conveys information about the source's relative distance. For very distant stationary objects, the high-frequency parts of their sound waves will be blocked by things in the air, leading to a muffled sound that reaches the listener

What is the chief criticism of the place theory?

For very low frequency sounds, the traveling wave has a very broad peak. This makes it difficult to discriminate between similar low-frequency sounds because they would produce similar waves in the basilar membranes.

What are formants? What properties of speech are associated with formants and formant transitions?

Formants correspond to vowels and formant transitions correspond to consonants

How do frequency theory and place theory each explain how sound frequency is encoded by the basilar membrane?

Frequency theory- the basilar membrane moves as a unit at a frequency that matches the frequency of a sound wave and this causes a neuron to fire at the same frequency. Place theory- the place along the basilar membrane at which the wave reaches its peak depends on the frequency of the sound

Describe the relationship between the fundamental frequency and the harmonics in a complex tone produced by a single source.

Fundamental frequency is the lowest frequency and harmonics are the higher frequencies.

fundamental frequency

How often the lowest frequency in a complex tone occurs; determines pitch

What is one way that human listeners might solve the segmentation problem?

If humans take long pauses between words.

What are the suggested roles of the inner and outer hair cells in hearing?

Inner- encoding info about frequency; outer- changing the way the basilar membrane moves in response to sound & sharpening.

inner ear

Made up of the cochlea,

outer ear

Made up of the pinna, auditory canal and the tympanic membrane.

middle ear

Made up of the small cavity, the ossicles, and the Eustachian tube.

Describe volley theory. How does volley theory address the criticisms of frequency theory?

Neurons firing, always at least one neuron firing, never the same one; together neurons can fire faster

What is the segmentation problem?

No gaps between words; the input you get doesn't separate words for you.

What determines which consonant or which vowel is produced?

Place of closure determines consonant; Vowels are determined by jaw movement.

What is the difference between a pure tone and a complex tone?

Pure tones are composed of a single frequency, and complex tones are composed of many.

acoustic reflex

Responds to loud sounds and dampensthe movements of the ossicles, which protects the auditory system.

Organ of Corti

Rests on top of basilar membrane and is covered by tectorial membrane; contains hair cells

movement parallax

Sounds from nearby sources appear to move more quickly as the listener moves through the environment.

directional transfer function

The difference between the sound wave as it's produced by the source, and the sound wave as it enters the ear. The notches and peaks are part of DTF.

acoustic shadow

The difference in intensity that forms the foundation of the interaural intensity difference due to location; When the head blocks sound from reaching the ear on the other side.

doppler shift

The doppler shift is the change in frequency of moving sound source

amplitude

The pressure difference between atmospheric pressure and the maximum pressure of the wave.

What is the Doppler shift, and why does it occur? What information does it provide to a listener?

The doppler shift is the change in frequency of moving sound source; waves bunch up or spread out and cause a change in pitch; it indicates the distance of a sound source that is moving toward or away from the listener.

Describe the tonotopic map on the basilar membrane. Where are high and low frequencies encoded?

The lower frequencies are encoded closer to the apex, and the higher frequencies are encoded to the base.

How does a vibrating object (such as a tuning fork) produce a sound wave?

The object creates an alternating pattern of high and low pressure ares in the air.

What is impedance mismatch, and why does it pose a problem for hearing?

The outer ear and middle ear has low impedance and the inner ear has high impedance. As a result, air pressure changes are poorly transmitted to liquid (inner ear).

apex

The part of the basilar membrane farthest from the middle ear.

base

The part of the basilar membrane nearest the middle ear.

tectorial membrane

The part of the basilar membrane nearest the middle ear.

pinna

The part of the ear that is visible on the outside of the head.

How do the properties of the traveling wave in the basilar membrane lead to encoding of particular frequencies?

The point along the membrane at which the peak occurs is a signal to the brain about what the sound's frequency is.

Hertz

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

How does the pinnae aid in localization?

They aid in localizing the elevation of a sound source. As the sound wave enters the ear, it bounces off the pinna. This enhances some frequencies and reduces the intensity of other frequencies. This produces notches (reduces frequencies) and peaks (amplified frequencies).

tonotopic map

individual fibers vibrate at specific frequencies along the cochlea

wavelength

inversely related to frequency- high frequency sound- short wv

outer hair cell

neurons in the Organ of Corti; serve to amplify and sharpen the responses of inner hair cells

inner hair cell

neurons in the organ of Corti; responsible for auditory transduction

scala vestibuli (vestibular canal)

one of the three chambers in the cochlea; separated from the cochlear duct by Reissner's membrane

scala tympani (tympanic canal)

one of the three chambers in the cochlea; separated from the cochlear duct by the basilar membrane

cochlear duct

one of the three chambers in the cochlea; separated from the tympanic canal by the basilar membrane; contains the organ of Corti

frequency theory

rate of vibration matches sound frequency.

helicotrema

small "hole" at apex; connects scala vestibuli to scala tympani

round window

small membrane that lets out pressure caused by fluid motion

stapes

stirrup; Transmits vibrations to the oval window

interaural time difference

time difference in when sound reaches ears depends on azimuth; sensitive to lower frequency

timbre

unique tonal quality produces by pattern of harmonics

Give two possible criticisms of frequency theory.

upper limit on firing rate of neurons, which doesn't factor in refractory period; basilar membrane does not vibrate as unit- variations in width and stiffness along the cochlea;