Sound measurements | |
---|---|

Characteristic | Symbols |

Sound pressure | p, SPL,L_{PA} |

Particle velocity | v, SVL |

Particle displacement | δ |

Sound intensity | I, SIL |

Sound power | P, SWL, L_{WA} |

Sound energy | W |

Sound energy density | w |

Sound exposure | E, SEL |

Acoustic impedance | Z |

Speed of sound | c |

Audio frequency | AF |

Transmission loss | TL |

**Sound exposure** is the integral, over time, of squared sound pressure. The SI unit of sound exposure is the pascal squared second (Pa^{2}·s).

## Mathematical definition

Sound exposure, denoted *E*, is defined by

where

- the exposure is being calculated for the time interval between times
*t*_{0}and*t*_{1}; *p(t)*is the sound pressure at time*t*, usually A-weighted for sound in air.

## Sound exposure level

**Sound exposure level** (SEL) or **acoustic exposure level** is a logarithmic measure of the sound exposure of a sound relative to a reference value.

Sound exposure level, denoted *L*_{E} and measured in dB, is defined by^{[1]}

where

*E*is the sound exposure;*E*_{0}is the reference sound exposure;- 1 Np = 1 is the neper;
- 1 B = 1/2 ln 10 is the bel;
- 1 dB = 1/20 ln 10 is the decibel.

The commonly used reference sound exposure in air is^{[2]}

The proper notations for sound exposure level using this reference are *L*_{W/(400 μPa2⋅s)} or *L*_{W} (re 400 μPa^{2}⋅s), but the notations dB SEL, dB(SEL), dBSEL, or dB_{SEL} are very common, even if they are not accepted by the SI.^{[3]}

## References

**^**"Letter symbols to be used in electrical technology – Part 3: Logarithmic and related quantities, and their units",*IEC 60027-3 Ed. 3.0*, International Electrotechnical Commission, 19 July 2002.**^**Ross Roeser, Michael Valente,*Audiology: Diagnosis*(Thieme 2007), p. 240.**^**Thompson, A. and Taylor, B. N. sec 8.7, "Logarithmic quantities and units: level, neper, bel",*Guide for the Use of the International System of Units (SI) 2008 Edition*, NIST Special Publication 811, 2nd printing (November 2008), SP811 PDF