ORE 654 Applications of Ocean Acoustics Lecture 6b Ocean Noise - PowerPoint PPT Presentation

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ORE 654 Applications of Ocean Acoustics Lecture 6b Ocean Noise

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ORE 654 Applications of Ocean Acoustics Lecture 6b Ocean Noise Bruce Howe Ocean and Resources Engineering School of Ocean and Earth Science and Technology – PowerPoint PPT presentation

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Title: ORE 654 Applications of Ocean Acoustics Lecture 6b Ocean Noise


1
ORE 654Applications of Ocean AcousticsLecture
6bOcean Noise
  • Bruce Howe
  • Ocean and Resources Engineering
  • School of Ocean and Earth Science and Technology
  • University of Hawaii at Manoa
  • Fall Semester 2011

2
(No Transcript)
3
Noise
  • Noise spectra
  • NL 10 log(ltInoisegt/Iref) dB re 1 µPa2/Hz
  • Classic
  • Urick curves

4
Ship noise
  • Radiated sound

Gerald DSpain
5
Low frequency noise - wind
Station ALOHA, 20 months
6
Bioacoustic sound
7
Offshore a military training base
DSpain
8
Measuring wind and rain
Nystuen
Nystuen
9
Large whales using SOSUS
All 6 yrs
10
Bowhead and beluga whale and walrus sounds
  • Spectrogram of under ice
  • northernBering Sea in May 2007

11
Comparison Wenz vs APL vs Ross
Ross Mechanics of Underwater Noise (1976)
Acoustics Bulletin (1993)
12
Simplified noise spectra
  • Low frequency flow turbulence/seismics/wave-wave
  • Shipping
  • Wind/waves

13
Simplified noise spectra - terms
  • Turbulence/microseisms
  • Shipping
  • Wind/waves
  • Thermal

14
Noise
  • Noise spectra
  • NL 10 log(ltInoisegt/Iref) dB re 1 µPa2/Hz
  • Bandwidth ?f
  • BW 10 log ?f
  • Total noise level NLtotal NL BW

15
SNR Budget
Acoustic Signal-to-Noise Ratio (SNR) Calculation Acoustic Signal-to-Noise Ratio (SNR) Calculation Acoustic Signal-to-Noise Ratio (SNR) Calculation

Enter values in yellow boxes

Value units Value Units
Acoustic source level 262 W 195.0 dB re 1 microPascal at 1 m
Range - spherical spreading 10000 m -80.0 dB
Absorption for center frequency 10000 Hz -10.8 dB
Scattering loss (3 dB/bounce) 0 bounces 0.0 dB
Total received signal 104.2 dB

Noise level 10000 Hz 52.0 dB/Hz
Noise in rms bandwidth 1000 Hz 30.0 dB
Total Noise 82.0 dB

Received SNR 22.2 dB

Coherent processing time 0.1 s
Processing gain 20.0 dB

SNR - 1 receiver 42.2 dB

SNR - n receivers 1 42.2 dB

Travel time precision 0.024351 ms

Sound speed precision 0.005479 m/s
Temperature precision 0.001370 K
Range precision 0.036526 m
N digits 100 digits
Time per digit 1 ms
Cycles per digit 10 cycles
16
Rms precision of peak locations
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