Underwater Acoustics - Measurements

Measurements

Sound in water is measured using a hydrophone, which is the underwater equivalent of a microphone. A hydrophone measures pressure fluctuations, and these are usually converted to sound pressure level (SPL), which is a logarithmic measure of the mean square acoustic pressure.

Measurements are usually reported in one of three forms :-

• RMS acoustic pressure in micropascals (or dB re 1 μPa)
• RMS acoustic pressure in a specified bandwidth, usually octaves or thirds of octave (dB re 1 μPa)
• spectral density (mean square pressure per unit bandwidth) in micropascals per hertz (dB re 1 μPa²/Hz)