S&P Exam 3: Chapter 12: Hearing in the Environment

What is azimuth?

coordinates left to right

What is elevation?

coordinates poisition up and down

What is distance?

coordinates poisition from observer

What is interaural level difference (ILD)? What frequency is ILD good for?

difference in sound pressure level reaching the two ears

high frequency sounds

What are binaural cues?

location cues based on the comparison of the signals received by the left and right ears

Describe Interaural time difference (ITD)?

difference between the times sounds reach the two ears

Good for localizing low-frequency sounds

Describe the Cone of Confusion.

points where ITD and ILD are the same, so location is ambiguous

What are Spectral cues?

differences in the spectrum of frequencies that reach each ear.

– Helps determine elevation

Describe the Spectral Cues Experiment.

• Right after molds inserted → poor

performance for elevation, azimuth

unaffected.

• After 19 days → performance for

elevation close to original performance

• Molds removed → performance stayed

high (both sets of cues were there).

• Suggests different neurons for each set

of spectral cues

True/False: Coincidence detectors fire

only when signals arrive from

both ears simultaneously.

True

True/False: Other neurons in the circuit

fire to locations not corresponding to other ITDs.

False

Narrowly-tuned ITD neurons in barn owls use ______ _____.

Place coding system

Broadly-tuned ITD neurons in mammals correspond with _______ ______.

Distributed coding system

What (________) stream- Identifying sounds

ventral

Where (______) stream- Locating sounds

(dorsal)

What is the Precedence Effect?

When there is only a short delay between sounds, the sound is perceived as coming from the first source only

What is the study of how sounds are reflected in rooms?

Architectural Acoustics

What is the time for sound to decrease to 1/1000th of its original pressure.

Reverberation time

What is the base ratio?

ratio of low to medium frequencies

What is the Spaciousness factor?

fraction of all perceived sound that is

indirect

What is Onset time?

sounds that start at different times are likely to come from different sources

What is Location regarding Separating the Sources of Sound?

A single sound source tends to come from one location

What is the similarity of timbre and pitch in regards to separating the sources of sound?

sounds with the same timbre and pitch are usually from the same source

True/False: Sounds with the same timbre and pitch are usually from the same source

True

What is the auditory stream segregation?

we group together sounds with same timbre and pitch

What is Proximity in time?

sounds that occur in rapid succession usually come from the same source

What is Auditory continuity?

sounds that stay constant or change smoothly are usually from the same source

Describe an example of vision dominating hearing.

Visual capture (ventriloquist effect) - observer perceives the sound as coming from the visual location rather than the source

Describe an example of hearing dominating vision.

Two-flash illusion: The brain prioritizes the precise timing of audio over the visual information, forcing the visual cortex to "see" a second flash that did not exist

When a single dot is flashed onto a screen, the participant perceives one flash

When a single beep is presented at the same time as the dot, the participant still perceives one flash

However, if the single dot is accompanied by two beeps, the participant sees two flashes, even though the dot was flashed only once

Echolocation results in: Activity in the ___________ for blind Echolocators and controls and activity in the ________ cortex for blind echolocaors only.

–auditory cortex

– visual cortex

Define the following aspects of auditory space- azimuth coordinates, elevation coordinates, and distance coordinates.

azimuth describes the location of sound from left to right

elevation describes the location of sound from up and down

distance describes the distance of a sound sound from the listener

Define and describe the following binaural cues for sound localization: interaural level difference (ILD) and interaural time difference (ITD). What are these different cues used for?

Interaural level difference is based on the difference in the sound pressure level of the sound reaching both ears

It is used for high-frequency sounds (greater than 3,000 Hz)

Interaural time difference is the time difference between a sound that reaches the left ear and when it reaches the right ear

it it used for low-frequency sounds

True/False: Most sounds in the environment contain high frequency components.

false

What are spectural cues? Describe the method and results of the spectural cues experiment.

Spectural cues are sound location cues that depend on one ear

In the spectural cues Experiment

1. Ears molds were inserted into the ears of particpants to interfere with established spectural cues.

2. After the ear molds were inserted, particpamnts performed poorly on sound locationalizing regarding elveation, but azimuth was not affected

3. After 19 days, their perforamnce for elevation became close to their original performance

4. When the ear molds were removed, the participants performance remained the same and both sets of cues were there.

The results were that the brain kept the original spectural cues

The spectural cues experiments suggests that there are different patterns for each set of spectural cues

Describe the Jeffress Model for how ITD works in the localization of sound.

The Jeffress Model proposes that neurons are wired so that each receives signals from both ears. As each signal travels along its axon, it stimulates each neuron in turn. When neurons within a circuit called coincidence detectors fire simultaneously, the interaural time difference (ITD) is equal to 0. Other neurons in the circuit fire to locations corresponding to other IDs.

Discuss the difference between the ITD neurons in birds vs mammals.

The ITD neurons in birds are narrow and use a place coding system (respond with sound reaches the left ear first)

ITD neurons in mammals are broadly tuned and use a distributed coding system (there are broadly tuned neurons in the right hemisphere that respond when sound comes from the left). There are also broadly tuned neurons in the left hemisphere that respond when sounds come from the right)

Describe the ventral and dorsal streams for sound localization.

the ventral stream is the “what” pathway and is used for identifying sounds

the dorsal stream is the “where” pathway and is used for locating sounds

Describe the difference between direct and indirect sound.

direct sound describes sound waves that reach your ear directly

indirect sound describes sound that reaches your ears after bouncing off another surface

Explain the precedence effect for sound localization.

When there is only a short delay between sounds, the sound is perceived as coming from the first source only.

Discuss some aspects of architectural acoustics that affect the quality of sound. (3)

concerned with how indirect sound (sound that bounces off a surface before reaching the ear) affects the quality of sound

reverberation time: the time it takes for the sound in a room to decrease to 1/1000th of its original pressure (or a decrease in level by 60 dB).

base ratio: the ratio of low frequencies to middle frequencies that are reflected from walls and other surfaces

spaciousness factor: the fraction of all of the sound received by a listener that is indirect sound

Discuss how we separate the sources of sound in our environment. (3)

Onset time: Sounds that start at different times are likely to come from different sources

Location: A single sound source tends to come from one location

Similarity of timbre and pitch: sounds with the same timbre and pitch are usually from the same source

Explain auditory stream segregation.

When high pitched tones are slowly alternated with low pitch tones, the listerner perceives two separate streams of sounds: one high pitched and one low-pitched

Describe the method and results of the Wafrren et al., Experiment on auditory continuity

1. Particiapants were presennted with burstd tone interrupted by gaps of silence

2. Listeners percived these tones as stopping during the silencer

3. When Warren filled the gaps with noise, the listerners percived the tone as continuing behind the noise

This demonstrated that a tone can be perceived as continuours even when interupted by bursts of noise

What is echolocation? Discuss the brain activation differences between blind echolocators and controls while using echolocation.

The production of sound waves to determine the location of objection

1. Activity in the auditory cortex for blind echolocators and

Controls in the auditory cortex for blind echolocators

2. Activity in the visual cortex for blind echolocators only