3.21  normalized 8-hour average sound level. Level of time-mean-square, A-weighted sound pressure during a normalization period Tn of eight hours, such that the sound exposure therefrom is equal to the sound exposure of a time-varying sound at a place where total sound exposure occurs within a time period not necessarily eight hours. Unit, decibel (dB); abbreviation, N8hL; symbol, LA8hn.

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