On 7/21/2010 5:20 AM, davimon100 wrote:
>
>
> Am I right in thinking that hydrophones are waterproof contact
> microphones? If so, it should be possible to hook a contact mic up to
> pick up surface vibrations on an object outside of water, right?
>
I think that the term "contact mic" can mean different things to
different people. To many, they think of a contact mic as a little brass
piezo bender disk. I suspect that this is what you are referring to.
These need to be flexed in order to generate significant output and work
in different modes of operation as contact mics. If bonded tightly to a
surface, they pick up only ripples resonating across the surface of
whatever you are trying to record. If they are pushed onto an uneven
surface, or the disk is supported around its perimeter, it can also more
effectively pick up the motion of the object in space perpendicular to
the disk. In this case it is working more like an accelerometer.
A hydrophone is a dynamic pressure transducer, similar to an omni mic.
They can be made from these piezo disks, but I wouldn't say that they
are the same. I don't know how your Dolphin Ear hydrophone is made, but
it looks and sounds like it uses at least one large piezo bender disk.
If this is the case, it might need to be flexed to generate a signal.
The epoxy potting material around the sensor will stiffen this up and
dampen its sensitivity. It should be designed to pick up pressure
differences, so it might be helpful to put something massive behind it.
Obviously, caution is essential not to break the hydrophone. You
certainly wouldn't want to do this with a hydrophone made from a
spherical of cylindrical piezo transducer.
Regards, Robb
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