Page 451 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

444 CHAPTER 16 Acoustic Positioning
FIGURE 16.16
Source
Reception threshold level
Noise level
Reception
Distance from sound source
An example of the reception of a signal below the noise and reception threshold level—signal is rejected.
FIGURE 16.17
Reception threshold level
Noise level
#1 #2 #3
Distance from sound source
Sample sound source relationships to the reception threshold and noise level.
above the noise level—the signal is received and is passed. In signal source 3, the source is above the noise level but below the reception threshold—signal is received but rejected.
The two relevant underwater acoustical environmental issues are: 1. Background noise
2. Reverberation/multipath
Background noise requires the transmitting beacon to possess a higher output in order to “burn through” the noise and be recognized by the receiver. Reverberation/multipath propagation causes
dB level dB level