Sound Pressure Level

Ten times the logarithm of the ratio of the time-mean-square pressure of a sound, in a stated frequency band or with a stated frequency weighting, to the square of the reference sound pressure of 20x10-6Pa.

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
There are a number of points that should be taken into account when measuring sound pressure level:

  1. measurement point in space relative to equipment being measured and/or surrounding environment.
    1. Sensitivity of location
    2. Operating condition and stability of equipment being measured

  2. dynamic range and frequency limitations of microphone and measuring equipment versus test requirements
    1. document for future reference
    2. compared to post processing requirements

  3. calibration of microphone
    1. calibration may need to be performed before and after measurement
    2. calibration frequecy and level versus measurement requirements

See also: Average Sound Pressure Level in a Room, dBA, dBB, Decibel, Logarithm, Loudness, Octave Band Level, Sound, Sound Level Meter, Sound Power Level.

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Subjects: Noise & Vibration