From WebRef.org

- Time-varying sound levels are often described in terms of an equivalent constant decibel level. Equivalent sound levels (L
_{eq}) are used to develop single-value descriptions of average sound exposure over various periods of time. Such average sound exposure values often include additional weighting factors for annoyance potential attributable to time of day or other considerations. The Leq data used for these average sound exposure descriptors are generally based on A-weighted sound-level measurements. - Source: http://www.volpe.dot.gov/acoustics/docs/1990-1999/1999-1.pdf (TEQ, denoted by the symbol L
_{AeqT}, also often referred to as LEQ): Ten times the base-10 logarithm of the time-mean-square, instantaneous A-weighted sound pressure, during a stated time interval, T (where T=t_{2}-t_{1}, in seconds), divided by the squared reference sound pressure of 20 • Pa, the threshold of human hearing.

L_{AeqT} is related to L_{AE} by the following equation:

L_{AeqT} = L_{AE} - 10 x log_{10}(t_{2}-t_{1})(dB)

Where L_{AE} = Sound exposure level

The L_{Aeq} for a specific time interval, T_{1} (expressed in seconds), can be normalized to a longer time interval, T_{2}, via the following equation:

L_{AeqT2} = L_{AeqT1} - 10 x log_{10}(T_{2}÷T_{1})(dB)

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