How fast does sound travel in water compared to air? Seems like for stereo
the best mike spacing should be the equivalent of ear spacing (6.5"
multiplied by the appropriate factor).
I know that in water, sound waves bend around objects easily, so one needs a
fairly large and dense boundary to create intensity differences between two
spaced mikes. Perhaps the boat hull could be used as a boundary, allowing
for a "binaural" sound experience.
If one does not use a boundary, the stereo effect will be based primarily on
time arrival differences, rather than intensity differences because the
microphones are ominidirectional.
Lang
David Kuhn wrote:
> Hello listeners,
> I've been recording Cetacean sounds when the opportunity arises.
> In Hawaiian waters are Humpback, False Killer, Pilot, Melon-head, and
> Sperm whales, and Spinner, Bottlenose, Rough-toothed, Spotted, and
> Striped Dolphins, and more. I get some beautiful sounds and want to
> get more, but so far snapping shrimp dominate my recordings. I use
> Cool Edit Pro's "click and pop removal" feature seems overpowered
> (detecting upwards of several hundred clicks per second!) and not
> able to clean them up adequately. I read that snappers are in depths
> up to 30 m.(Can anyone confirm that info?), so I'm heading for deep
> water, but would like to salvage what I've got.
When I lived in Hawaii, I spent large amounts of time out in the water.
The snapping shrimp were more common in the lagoon than outside the
reef, but were both places. I dove well over 100' at some offshore
islands that dropped straight down underwater, and they were there too.
And underwater their high energy snap would travel well.
Have you checked if they are confined to frequencies you can filter
out? Check a sonogram and see. Certainly if you filtered all frequencies
except the call ones you wanted that should tone them down at least.
> Another question: Most of my in-the-air recordings are stereo. Is
> hydrophone stereo feasible, using mic's at either end of a 60' boat?
Speed of sound is faster in water, and the water surface is a reflector.
If the boat is in deep water it might work. Work like you are using
spaced omni's but much farther apart. Definitely try each end of the
boat first.
And let us know how you do.
Walt
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