underwater sound reference division ultrasound

To make a comparison of these underwater sound pressure levels with the values quoted for sounds in air an important point must be addressed. Comparison of underwater and airborne sound Typical Sound Pressure Levels for various sources. Typical active sonar transmission level Beluga whale call (1m) Cavitation begins to occur at the face of transmitters.

Spreading loss is 6 dB for each doubling of the distance from the source, so a level of 200 dB at 1 m will have dropped to 194 dB at 2 m and to 158 dB at 128 m and so on. A few values at other distances are provided in the table to demonstrate the effect of spherical spreading of the sound waves. Measurements are standardised to refer to the sound pressure level at a distance of 1 m from the source. For narrow band signals such as sonar transmissions the broadband level will be the same as the spectral level at the transmission frequency since all the power in concentrated at this frequency, but for a broadband source like a large merchant ship, the typical spectral level will be about 160 dB re 1µPa/Hz and the total power received over a 10 kHz band will add 40 dB yielding a measured value of about 200 dB re 1µPa. The sound pressure levels in the table are broadband measurements, where all frequencies from a few Hz to a few kHz contribute. Broadband versus narrow band measurements Sound sources typical of some of these levels are shown for comparison. Set out below is a table of sound pressure levels in order-of-magnitude steps.

Underwater sound reference division ultrasound