How does a hydrophone work?
Here, we explain – how does a hydrophone work? They are measuring instruments and a type of underwater microphone, that are designed to monitor underwater noise. Hydrophone work by transducing (converting) sound waves to electrical voltage. This is achieved by detection of pressure changes in the surrounding environment. The combination of speed over distance, at which the sound wave travels through water or fluid, is proportionate to the changes in pressure, which will in turn reflect the nature of the electrical output transmitted. Piezoelectric materials are considered ideal for the building of hydrophones. This material can change its form and helps to generate ‘electrical potential output’ in response to mechanical or external pressure variations.
Through the application of an electrical voltage to a crystalline ceramic type material, the crystalline structures align, and they then become anisotropic and carry an electrical charge. Airborne sound waves are easily registered by a hydrophone, however they become less sensitive when submersed in fluids due to a poor ‘acoustic impedance match’. A standard hydrophone can be built with a transducer. The transducer is proved to be fundamental in helping the conversion of the incoming sound waves into an electrical voltage.
The use of piezoelectric transducers as an alternative to crystal materials are now the popular technology option in engineering a modern-day hydrophone.
Hydrophone work using a single transducer which have a circular conical type shape that will reflect incoming sound waves. This, in turn, will permit the hydrophone to be positioned at varying locations and depths. The weak point in using a single transducer is that signals from all other directions can interfere with the main signal, and so cannot be subtracted from the targeted signal. This can therefore give obscure data results.
A small, single, cylindrical ceramic underwater acoustic transducer is able to achieve perfect omni-directional pickup. A directional hydrophone will increase sensitivity from any direction using two of these basic techniques: