Localisation And Binaral Hearing

Question 1

Name the mechanism used to localise sound?

Answer 1

Interaural intensity difference (IID)
Interaural Timing difference (ITD)
Pinna effects

Question 2

What is the head shadow effect?

Answer 2

Sounds coming from one side sometimes your own head can get in the way of it reaching the ear furthest away. Effects IID and ITD
Can be overcome by turning head
More prominent for high frequencies

Question 3

What is the cone of confusion?

Answer 3

Cone shaped set on points radiating out from the midway between a persons ears produce identical phase delays and level differences so to listener IID and ITDs
Therefore accuracy and precision of locating the sound source.

Question 4

Human ears work best on the horizontal plane?

What are main contributors

Answer 4

Horizontal

ITD and IIDs main contributors

Question 5

Pinna effects are main contributors to hearing on a ______plane

Answer 5

Vertical plane?

Question 6

What are PAM

Post-auricular muscles

Answer 6

Attached to the pinna in many animals. Allows some to prick ears up turn pinna towards direction to localise sound. Humans have them however can not use these to localise sound.

Question 7

What is the difference between
Localisation
Lateralisation

Answer 7

Localisation - sounds out in environment

Lateralisation- where it is hear internally (left,right ear or centrally)

Question 8

What is the Doppler effect?

Answer 8

The apparent change in frequency of a wave caused by relative motion between the source of the wave and the observer

E.g. Think siren effect as siren gets closer waves closer together higher pitch. Siren moves away waves become further apart (lower frequency)

Question 9

Why is listening with two ears better than one?

Answer 9

Binaural summation (less gain/effort required)
Improved ability to pick speech out of noise better (better SNR)
Improved frequency selection
Better discrimination and processing
Aiding both ears also reduces auditory deprivation
Improved localisation and better awareness of distance of sound

Question 10

What is binaural fusion/ integration

Answer 10

A process where sound are fused into a coherent image

E.g. Can be used for stenger test

Question 11

Stenger test, how to conduct

Answer 11

Silmuntaneously
In worse ear:Present tones of 20 dBs lower than threshold of the better ear
In better ear:Present tones of 20 dBs higher than threshold of the better ear

Put stops pressing when they lose sound in good ear to worse. Would not notice shift in lateralisation if true loss

Question 12

What is binaural summation/loudness?

Answer 12

SOUND IN BOTHE EARS BETTER THAN ONE

Sound presented to both ears is usually perceived as being louder than to just one ear
Binaural summation usually 3dBs louder when binaural than monaural
Loudness summation depends on intensity and bandwidth area of the excitation of the basilar membrane

Question 13

What is the precedence effect?

Or law of the first wavefront?

Answer 13

When a sound is followed by another sound separated by a sufficiently short time delay listeners perceive a single auditory event.
If there is a delay of lag the second sound can effect localisation however its effect is suppressed by first arriving sound

Question 14

Methods of intensity discrimination in cochlea

Answer 14

Webbers law
Phase locking
Spread of excitation

Question 15

Methods of frequency discrimination in cochlea?

Answer 15

Tonotopic organisation
Place coding
Time place
Traveling wave

Question 16

What is diplacusis?

Answer 16

Hearing disorder where a single auditory stimulus can result in sound of different pitches being perceived in both ears.
Can result from SNHL
trauma
Infection
Neuroma