On 5/10/2012 6:06 PM, Robb Nichols wrote:
> There are a couple of practical things to consider: Low frequencies do
> not seem to propagate well near the surface. I have to admit that this
> is an observed phenomenon; I've never really studied it. I suspect that
> it is relative to the depth of the hydrophone being at least half a
> wavelength from the surface. But you can hear it easily as you lower a
> hydrophone into the water, if your hydrophone is linear at low
> frequencies. Mitch, do you know more about this?
>
>
About all I can contribute to your comment is that surface effect as a
reflection causing phase cancellation is an issue... We used towed
hydrophone arrays for geophysical profiling and would used winged
weighted depressors on the towed end of an array to hold them at a
specific depth below the surface. This depth was calculated to control
the effect of the surface reflection vs the bottom reflection to get the
highest resolution bottom data... The depths used are typically in the
order of a few of meters as I recall...
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Mitch Hill
(Sent from HP DV6T)
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