Sound Pressure Level

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The term most often used in measuring the magnitude of sound. It is a relative quantity in that it is the ratio between the actual SOUND PRESSURE and a fixed reference pressure. This reference pressure is usually that of the THRESHOLD OF HEARING which has been internationally agreed upon as having the value .0002 dynes/cm2.

SPL may be measured with a SOUND LEVEL METER weighted according to a specific frequency response pattern and termed SOUND LEVEL. The electroacoustic equivalent to SPL is measured with a VU METER.


Change in Sound Pressure Level dBApproximate change in acoustic pressurepercentage change in acoustic pressureHuman Subjective Reaction
1dB1.110%Can′t detect
3dB1.440%Minimum change we can remember
6dB2.0100%Pressure doubling, significant change
10dB3.3330%Subjective doubling
20dB10.01000%Very noticeable change

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