Sound Pressure Level
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 dB||Approximate change in acoustic pressure||percentage change in acoustic pressure||Human Subjective Reaction|
|3dB||1.4||40%||Minimum change we can remember|
|6dB||2.0||100%||Pressure doubling, significant change|
|20dB||10.0||1000%||Very noticeable change|
— Source: http://www.diracdelta.co.uk