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.
— Source: SOUND PRESSURE LEVEL (SPL) http://www.sfu.ca
| Change in Sound Pressure Level dB | Approximate change in acoustic pressure | percentage change in acoustic pressure | Human Subjective Reaction |
| 1dB | 1.1 | 10% | Can′t detect |
| 3dB | 1.4 | 40% | Minimum change we can remember |
| 6dB | 2.0 | 100% | Pressure doubling, significant change |
| 10dB | 3.3 | 330% | Subjective doubling |
| 20dB | 10.0 | 1000% | Very noticeable change |
— Source: http://www.diracdelta.co.uk