Dear list members,
I am writing to ask you help to identify a strange underwater noise.
I use a wide-band two-elements (Benthos AQ4 sensors) towed array to
listen and track some species of cetaceans in the Mediterranean Sea. The
system also includes two pre-amplifiers, a pressure sensor for depth
readouts and a final amplifier connected to an external E-MU audio board
feeding to the PC. I use 96 kHz or 192 kHz sampling frequency, depending
on the species I am dealing with
Lately I am experiencing a weird unknown broadband click-like noise with
a clear repetition pattern (some audio files can be downloaded at
https://www.dropbox.com/sh/7tyf5vhoveekg4o/tddu9ouHGP). The noise starts
with a small inter-click-interval, pauses for a few seconds and restarts
always with an increased inter-click-interval, into a continuous loop
that always restart with the same inter-click-interval. I observed no
significant changes in the frequency domain during the loop.
Interestingly the sound appears mostly when the research boat stops and
the hydrophone sinks between 50 and about 200 m. As soon the boat moves
and the array rises up towards the surface, the noise disappear.
I have been told that noise could be due to an intermittent connection
of the Depth Meter, which does result in strange noise being seen in the
acoustic channels. If this is the case, how can I test any potential
failures of the pressure sensor/depth reader without disassembling the
whole system? If the component failure is not the main cause of the
noise, what could possibly be the origin of those clicks? Any advice and
suggestion will be greatly appreciated.
Best regards,
Nino
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Nino Pierantonio
Mobile: +39 349.532.9370
Skype: pierantonio_nino
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