Wikipedia

# Sound exposure

**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).

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 |

Audio frequency | AF |

Transmission loss | TL |

Sound exposure, denoted *E*, is defined by

- $E=\int _{t_{0}}^{t_{1}}p(t)^{2}\,\mathrm {d} t,$

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.

For other uses, see Sound level.

**Sound exposure level** (SEL) 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^{}

- $L_{E}={\frac {1}{2}}\ln \!\left({\frac {E}{E_{0}}}\right)\!~\mathrm {Np} =\log _{10}\!\left({\frac {E}{E_{0}}}\right)\!~\mathrm {B} =10\log _{10}\!\left({\frac {E}{E_{0}}}\right)\!~\mathrm {dB} ,$

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^{}

- $E_{0}=400~\mathrm {\mu Pa^{2}\cdot s} .$

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 notationsdB SEL,dB(SEL), dBSEL, or dB_{SEL} are very common, even if they are not accepted by the SI.^{}

- "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