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[Miguel Dahl]

Hi,

A very specific question I've not been able to figure out of, and the question doesn't belong in the in the other groups I guess..

I want to build some high quality hydrophones. I found a recipe for it and what components to be used, and got an understanding why they should be used.
But one thing I can't figure out of is exactly why one would want to use a compound with the same density (specific gravity, SG) as the water?

What happens if I mold the piezo in a compound with a higher or lower density than the water I'm submerging it into? Defraction, refraction etc.. But what happens, what's the result?

[Stephen Swaffer]

Speculating a bit-I know that fish/depth finders sometimes will be affected and see thermoclines-temperature differences with slight density changes.  Since they work on reflections I would assume some of the signal is reflected by the density change.  Reflected would imply a loss of sound energy and thus a loss in sensitivity of the mic in your case.

[Miguel Dahl]

Speculating a bit-I know that fish/depth finders sometimes will be affected and see thermoclines-temperature differences with slight density changes.  Since they work on reflections I would assume some of the signal is reflected by the density change.  Reflected would imply a loss of sound energy and thus a loss in sensitivity of the mic in your case.

Ooh, reflections. a sound wave propagating through a medium, meets a medum of higher density, higher frequencies are reflected, or attentuated? That opened up in some sense.
Just like you can hear more of the lower frequencies through a wall, while higher frequencies doesn't carry through because of lower energy.

So, a higher density could mean more reflections = attanuation of higher frequencies.

I think I just understood it, if it's about that.

[John Roberts {JR}]

Just like terminating RF lines with same impedance  to maximize signal transfer....

JR

[Mike Caldwell]

Sound waves in water will change speed and direction when hitting different water temperatures and densities.
By monitoring the water characteristics submarines can hide in different water layers.

[ProSoundWeb Community]