The deciBel Scale for Underwater Applications
The fundamental unit of sound pressure is the Newton per square metre or Pascal. However, in expressing underwater acoustic phenomena it is convenient to express the sound pressure through the use of a logarithmic scale termed the Sound Pressure Level. There are two reasons for this:
The Sound Pressure Level, or SPL, is defined as:
For example, a pressure of 1 Pa would be expressed as 120 dB re 1 µPa.
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