At 09:51 AM 11/8/2002 -0500, you wrote:
>How fast does sound travel in water compared to air?
Speed of sound:
Air: 1090 ft/sec
Water: 4800 ft/sec
factor increase in wavelength = 4.4
Drew
>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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