Sound exposure is the integral, over time, of squared sound pressure. The SI unit of sound exposure is the pascal squared second (Pa2·s).
Sound measurements | |
---|---|
Characteristic | Symbols |
Sound pressure | p, SPL, LPA |
Particle velocity | v, SVL |
Particle displacement | |
Sound intensity | I, SIL |
Sound power | P, SWL, LWA |
Sound energy | W |
Sound energy density | w |
Sound exposure | E, SEL |
Acoustic impedance | Z |
Audio frequency | AF |
Transmission loss | TL |
Mathematical definition
editSound exposure, denoted E, is defined by
where
- the exposure is being calculated for the time interval between times t0 and t1;
- p(t) is the sound pressure at time t, usually A-weighted for sound in air.
Sound exposure level
editSound exposure level (SEL) is a logarithmic measure of the sound exposure of a sound relative to a reference value.
Sound exposure level, denoted LE and measured in dB, is defined by[1]
where
- E is the sound exposure;
- E0 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 LW/(400
References
edit- ^ "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