Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Marine Geomatics > Underwater Acoustic Principles > Flashcards

Underwater Acoustic Principles Flashcards

1
Q

Sound is what kind of wave?

A

A pressure wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why kind of particle motion occurs from pressure waves?

A

Longitudal Oscillation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What 2 things does speed of sound depend on?

A
  1. Distance between molecules

2. Strength of intermolecular interactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Speed of sound increases with what 2 things?

A
  1. Temperature

2. Density

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the 5 characteristics of sound waves?

A
  1. Amplitude
  2. Frequency
  3. Speed
  4. Wave Length
  5. Intensity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is amplitude?

A

The distance from the resting state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is intensity?

A

The amount of energy per second crossing a unit area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is frequency?

A

The rate of oscillation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Waves with similar phase interact…….

A

Constructively

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Waves with opposite phase interact……

A

Destructively

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Give 6 things that affect SV

A
  1. Temperature
  2. The Coastal Environment
  3. Tidal Mixing
  4. Upwelling
  5. Salinity
  6. Depth
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What has the greatest influence on SV?

A

Temperature then salinity then depth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What influence does temperature have on SV?

A

4.5m/s per 1 Deg Increase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What influence does salinity have on SV?

A

1.2m/s per one ppt Increase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What influence does depth have on SV?

A

1m/s per 60m of depth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the combination of absorption and scattering known as?

A

Attenuation

17
Q

What does spherical spreading cause?

A

A spreading of sound waves in all directions, uniformly, which decreases intensity and weakens the signal

18
Q

What is Target Strength?

A

The ability of an object to reflect sound

19
Q

What 3 things does Target Strength depend on?

A
  1. Reflectivity
  2. Size
  3. Aspect
20
Q

How does the Receiving Directivity Index influence an acoustic signal?

A

It affects the systems ability to detect an acoustic pulse, by filtering out noise in the water column, it facilities a stronger gain from the target

21
Q

Give 3 sources of noise with definitions

A
  1. Ambient (any sound not emitted by the source of interest)
  2. Self Noise (any sound emitted by the source of interest)
  3. Reverberation (persistence of sound in a particular space after the original sound is produced)
22
Q

What is acoustic impedance?

A

How well the medium facilities sound energy to pass through

23
Q

What would a reflection coefficient of 0 mean?

A

Weak reflecting surface

24
Q

What would a reflection coefficient of 1 mean?

A

Very strong reflecting surface

25
Q

What would a reflection coefficient of 0.2 mean?

A

Sand

26
Q

What would a reflection coefficient of 0.6 mean?

A

Clay

27
Q

What would a reflection coefficient of 0.8 mean?

A

Rock

28
Q

What would a reflection coefficient of 0.9 mean?

A

Steel

29
Q

Give 4 points about Low Frequency Sonar

A
  1. Effective transmission of the pulse
  2. Some seabed penetration
  3. Large footprint but reduced resolution
  4. Long range capability
30
Q

Give 4 points about High Frequency Sonar

A
  1. Energy is easily dissipated in the water column
  2. Very little penetration
  3. Narrow beam and good resolution
  4. Decreased range capability
31
Q

What is the typical frequency of a Low Frequency Sonar?

A

30-35 kHz

32
Q

What is the typical frequency of a High Frequency Sonar?

A

200-220 kHz

33
Q

What is active sonar?

A

A system that transmits and receives

34
Q

What is passive sonar?

A

A listening device

35
Q

What does the sonar equation do?

A

It tells you whether target detection is possible using echo excess (EE = SL - TL + SG - DT) if EE > or = to 0 then it will be detected

Marine Geomatics (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions