Acoustics

Question 1

What are the three orders of marine mammals?

Answer 1

-Cetaceans (Odontocetes 68 and Mysticetes 11)
-Sirenia
-Carnivoria

Question 2

Why is sound the primary sensory mechanism?

Answer 2

-Low light penetration
-Biological species and particulates
-Sea state

Question 3

How far can sound propagate?

Answer 3

From metres to 1000s km

Question 4

Describe higher frequencies.

Answer 4

Higher frequencies give increased resolution but over a limited distance

Question 5

How is sound detected by a receiver underwater?

Answer 5

Detected by a receiver as changes in pressure

Question 6

How are acoustic waves characterised?

Answer 6

By their
Amplitude
Frequency
Wavelength
Phase speed
Intensity

Question 7

What is the amplitude?

Answer 7

Proportional to the maximum distance a vibrating particle is displaced from the rest

Question 8

What is a wavelength?

Answer 8

Is the distance between two successive compressions

Question 9

What is the frequency?

Answer 9

Is the rate of oscillation of the wave

Question 10

What is one hertz equal to?

Answer 10

Equal to one vibration per second

Question 11

What is the speed of sound in water?

Answer 11

1500 m per second

Question 12

Does speed of sound decrease with depth?

Answer 12

Speed decreases

Question 13

What is the absolute auditory threshold?

Answer 13

Is the minimum received sound level at which a sound with a particular frequency and other properties can be perceived in the absence of significant background noise

Question 14

What is the hearing range of a harbour porpoise?

Answer 14

130 kHz or 130,000 vibrations per second

Question 15

What sounds are mysticetes mainly sensitive to?

Answer 15

Low and moderate frequency sounds
-12 Hz to 8 KHz

Question 16

What purposes do cetaceans use sound for?

Answer 16

-Detecting predators
-Detecting prey
-Orientate and navigation
-Detect and decode calls from conspecifics

Question 17

What are the three odontocete sounds?

Answer 17

-Whistles
-Bangs
-Pulses or clicks