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Hydrophone Handbook

         Choosing a Hydrophone

 Maximum Dynamic Pressure and Intensity
 There are two general considerations for determining the
 maximum pressure at which a hydrophone can be used: (1) the
 linearity of its preamplifier, and (2) hydrophone damage.

 1. Linearity of Preamplifier
 Amplifiers have a voltage limit, beyond which they become non-
 linear and saturate. This is a reversible problem. That is, if it
 happens it does not damage the hydrophone or preamp.
 Although the data is invalid, the hydrophone can still be re-used
 within the amplifier’s specified voltage range. For Onda’s
 modular amplifiers (i.e., AH-20x0, AG-20x0, and AH-1100), a
 maximum voltage output is provided as a specification. The
 formulas to calculate loaded sensitivity can be used to
 determine the expected acoustic pressure level of the signal to
 verify they will be within the linear range of the amplifier. For
 high-sensitivity hydrophone models, Onda also offers a signal
 attenuator (i.e., ATH-1000) to prevent preamplifier saturation.
 For membrane hydrophone models which have an integral
 preamplifier, the maximum linear pressure range is also
 provided as a specification.

 2. Hydrophone Damage
 Unlike preamp linearity, damage thresholds are much more
 difficult to provide. Hydrophones are intrinsically fragile,
 particularly near the sensing element, because they are
 designed to have high sensitivity to detect transient pressures.
 Different models have varying degrees of protection depending
 on the construction. To add to the complexity, the robustness of
 each hydrophone depends on several factors in the test

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