Sound delays

Question 1

What is the interaural time difference ?

Answer 1

The difference in arrival time of a sound between two ears.

Question 2

What does the interaural time difference depend on ?

Answer 2

Position of the sound source

Distance between ears.

Question 3

What does the interaural time difference tell us ?

Answer 3

The direction or angle of the sound source

Question 4

What is hyperboloid ambiguity ?

Answer 4

A shape which represents all the possible places that the sound source could be.
(all points have same time delay)

Question 5

What is Interaural intensity difference ?

Answer 5

Where the head creates a sound shadow with respect to direction (fainter on one side)

Question 6

What queues do our ears use to localise sound ?

Answer 6

Interaural time difference
Interaural intensity difference
Interaural spectral differences

Question 7

If the sound is fainter on one side of the head…..

Answer 7

This will be due to the acoustic shadow produced by the head.
IID

Question 8

What will happen to IID below 200 Hz ?

Answer 8

Will not occur- no acoustic shadow as the wavelength is larger than our head.

Question 9

Where do intensity frequencies work well ?

Answer 9

High frequencies

But useless for low frequencies as no acoustic shadow

Question 10

How species improve interaural intensity difference ?

Answer 10

Earlobes

e.g. Hare-Can direct Pinna to scan where sound coming from

Question 11

What are interaural spectral differences ?

Answer 11

Structural designs of the ear which channel each sound wave in 2 or more independent pathways

Question 12

Why do our earlobes have ridges ?

Answer 12

h

Question 13

Describe the path of a sound wave entering the ear from the front.

Answer 13

Sound wave enters ear-
Also reflects off ridge creating seperate sound wave which also reaches drum, but slightly later
Sound overlap & interference occur

Question 14

What is interference in ISD ?

Answer 14

When separate frequencies superimpose/Overlap;
Some cancel out
Others are amplified

Question 15

How does interference enable localisation of sound ?

Answer 15

Our brain associates certain spectral notches (interference) with directions.

Question 16

What is the most powerful localisation queue in mammals ?

Answer 16

Interaural spectral differences

AKA- Spectral notches.

Question 17

Give an overview of interaural spectral differences.

Answer 17

Pinna creates multipath propagation
Interference occurs
Creating spectral notches
These are direction specific enabling localisation of sound

Question 18

How can we utilise the frequencies of spectral notches ?

Answer 18

Enable us to localise sound

Place both left and right ear on same diagram- find unique position (overlap)

Question 19

Give some of the reasons for improving IID, ITD, ISD ?

Answer 19

Marine traffic 
Prevention of ship collisions in fog.
WW1 
Detect fighter planes
Sound mirrors- Dungeness

Question 20

Improvements to sound localisation for WW1 usually involved ?

Answer 20

Construction of large structures- Large ears.
To improve hearing ability
(detection of fog horns)