Aud Sci Final

Binaural summation

Performance is better on a perceptual task when stimuli are presented binaurally vs monaurally

Based on spectral representation of the stimulus (information contained in the spectrum).

Place Model

Pitch is perceived based on maximum excitation along the basilar membrane.

Place Model

Binaural Fusion

Separates signals from each ear are perceived as single, fused auditory image.

Bundles of auditory nerve fibers fire at the compression phase of a signal, giving the brain a cue for the period of the signal.

Temporal Model

Binaural Squelch

The auditory system takes advantage of information received from both ears with different SNRs

Better Ear Effect

The auditory system takes advantage of the fact that one ear has a more favorable SNR

True or false: Once an effective masking level is obtained (the point at which masking occurs), the amount of masking increases linearly with increases in the level of the masker

True

True or false: With cochlear outer hair cell loss, the shape of the auditory filter is affected. The sharp tip is lost, and the shape of the filter broadens. This leads to increased vulnerability to masking and a less finely-tuned system.

True

Basilar membrane is modeled as

a bank of overlapping filters

Sound source localization

a listeners ability to identify the location or origin of a detected sound in direction and distance

What is the "cocktail party effect?" (Cherry, 1953)

ability to attend to a target in the presence of competing noise

RMS amplitude

average dB SPL of a stimulus

signal and masker are presented to opposite ears; the masker in the opposite ear increases the threshold of the signal

central masking

this masking takes place in the binaural auditory neural pathway

central masking

Immittance

describes the ease with which energy flows

Impedance

describes the opposition to energy flows

Frequency selectivity refers to the auditory system's ability to

detect one sound in the presence of another, different sound

nonlinear system

disproportionate change in input and output

Physiological tuning curves measured:

electrode at a certain place, measure response to varying tones at varying intensities

ossicles vibrating because of music

forced vibration

table vibrates when the stem of a vibrating tuning fork is placed on it

forced vibration

guitar strings being plucked

free vibration

tuning fork after being hit with a soft mallet

free vibration

Admittance

general term describing the flow of energy

If a sound is located at 00 elevation, where is the location of the sound?

in front of the nose

harmonic distortion

input level exceeds maximum output level

A tube that is open at one end has a resonant frequency because of standing waves. If the length of the tube increases, what happens to the resonant frequency?

it shifts to a higher frequency

5 ms ramped rise time/fall time

measure to avoid spectral splatter

In which of the following types of sound fields would the inverse square law NEVER apply?

near field

If a sound is located at 900 azimuth, where is the location of the sound?

near the right ear

The response of a healthy basilar membrane to varying levels of sound input is...

nonlinear/comprehensive

linear system

proportionate change in input and output

monaural masking; target signal and masker are presented simultaneously

psychoacoustic masking

this masking takes place in the cochlea

psychoacoustic masking

The masking level difference

signal threshold is improved when tones to each ear are out of phase

masker

sound increasing threshold of other sound

partial masking

sound is perceived as softer but still audible

test signal; probe signal (maskee)

sound that is being masked

the masker is presented either before or after the signal or target

temporal masking

the precise mechanism of this type of masking is unknown but it is presumed to be neural and not cochlear

temporal masking

Loudness Summation

the ability to improve perceptual performance seen on psychoacoustic tasks

amount of masking

the amount in dB of the threshold shift

Binaural fusion

the brain recieves information from both ears yet the stimulus is perceived as a single auditory image

Tuning curve

the shape of a graph showing the threshold of a single fiber of the auditory nerve plotted against the frequencies of sound to which it responds

Dichotic

the signal delivered to each ear differs in one or more dimensions

Diotic

the signal delivered to each ear is exactly the same in all aspects

Frequency Distortion

Amplitude is reduced at certain frequencies based on the characteristics of the filter

Harmonic Distortion

Distortion products are added which are harmonics of the original sound

What does it mean when we say the cochlea is modeled as a bank of overlapping filters? Select the best answer.

Each place along the basilar membrane will respond optimally at a "best frequency" but will respond to other frequency inputs at higher levels,

If you added mass to the middle ear system, would it make it harder or easier for high frequency sounds to be transmitted to the cochlea?

Easier

is a high frequency cue

ILD

Transient distortion

Spectral splatter

All else being equal, what type of masker would be a more effective masker? steady-state masker, where amplitude does not vary significantly fluctuating masker, where amplitude ranges from 0 to a maximum point and does vary quite a bit

Steady state masker

Based on the waveform of the stimulus.

Temporal Model

Frequency Selectivity

The ability to perceive separately multiple frequency components of a complex sound

(True/False) At cochlear dead regions, soft sounds at that particular frequency are NOT turned into neural signals.

True

Broadly tuned systems are efficient sound transducers.

True

Masking

increase in threshold/threshold shift in presence of another sound

Cochlear dead regions are due to a loss of

inner hair cells

Psychoacoustic tuning curves measured:

through masking

Echo suppression

"copies" of sounds in a reverberant room do not interfere with hearing because of this

Calculate the signal-to-noise ratio (SNR) You are carrying on a conversation with a friend next to a noisy piece of equipment. Your friend's voice (RMS amplitude) is 65 dB SPL as it reaches your ears. The level of the noise coming from the equipment is 60 dB SPL as it reaches your ears. What is the SNR?

+5 dB

Under what conditions might temporal masking arise?

- Occur when the masker and test signal do not overlap in time · Temporal masking, backward masking, forward masking - Sounds of speech may mask subsequent sounds (vowels may mask consonants in running speech)

Under what conditions might central masking arise?

- When a masker is presented to one ear can cause a threshold shift for signal at the other ear - BINAURAL AUDITORY PATHWAYS - More in high-frequency tones than low (5-10dB)

Off-Frequency Listening:

-A tone is detected (heard) away from the region of peak basilar membrane vibration -Pure tone signal is audible but basilar membrane response is remote from the center frequency -Tone is detected by IHC at the edge of the dead region

What three factors influence the amount of masking?

-Intensity of the masker -Relationship between the spectral characteristics of the masker and the signal (sound being detected) -Temporal characteristics of the masker (fluctuations in amplitude over time vs steady)

If the intensity of a sound 10 meters from the source is 36 watts/m2, what is the intensity 20 meters from the sound source in watts/m2? (Assuming no reverberations or other changes in sound intensity.)

18

If an unmasked threshold was 50 dB SPL and a masked threshold was 80 dB SPL, what is the amount of masking?

30 dB

The unmasked threshold is 15 dB SPL, masked threshold is 55 dB SPL, what is the amount of masking?

40 dB

A sound 25 feet from the source measures 60 dB SPL. What is the sound level in dB SPL 50 feet from the source, assuming no reverberations or obstacles? Enter the number only.

54

We see that a 1000 Hz tone can mask a 2000 Hz tone above certain presentation levels. What is the approximate amount of masking at 2000 Hz when the 1000 Hz tone is presented at 100 dB? Select the closest answer. (refer to images in class)

60

Why is a broader filter more susceptible to masking?

Auditory filters increase in width in the higher frequencies regardless of the cochlear outer hair cell status

What does it mean when we say the cochlea is modeled as a bank of overlapping filters?

Each place along the basilar membrane will respond optimally at a "best frequency" but will respond to other frequency inputs at higher levels

According to our current understanding of measuring perceptual sensitivity, a subject or patient would never respond to a stimulus presented below threshold. Therefore, any response to a soft input must be threshold.

False

The human auditory system is equally sensitive at all frequencies between 20 Hz and 20,000 Hz.

False

True or false: When masking a pure tone, it is important to use the widest bandwidth of noise available

False

True or false: When masking a pure tone, it is important to use the widest bandwidth of noise available.

False

Describe Fletcher's critical bandwidth experiment. What question was he trying to answer? What were his findings?

Fletcher first studied the question of "how much white noise actually contributed to the masking of a tone? His findings were confirmed. - A tone can be masked by: o Another tone o A narrow band of noise o A wide band of noise

arises due to the head shadow effect

ILD

based on phase differences of signal arriving at each ear

ITD

is a low frequency cue

ITD

Explain upward spread of masking and why we do not see significant downward spread of masking (from a physiologic perspective)

In the cochlea, low frequency masker IS able to envelop a high frequency masker - High frequency masker CANNOT encompass low frequency masker - Low → High ; High → Low

ILD

Interaural Level Differences → reflections causing a head shadow

ITD

Interaural Time Differences → diffraction around the head

When the graph shows a decrease at the cutoff frequency, what type of filter does it represent?

Low-pass filter

What are two characteristics that must be present for something to vibrate?

Mass and Elasticity

What provides better hearing in noise?

-spatial separation of target signal and noise -binaural squelch -better ear advantage