任意不規則変動音のL_<eq>評価量に及ぼすサンプル間隔の統計的影響(理論と実験)

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The well-known equivalent sound level (L_<Aeq>, abbr. , L_<eq>) adopted for a unified acoustic description of environmental noise by ISO 1996 has now gained some widespread acceptance, for example, as a measure of sound exposure. Nevertheless, in a theoretical study of L_<eq> statistics, considerable efforts must be yet spent for establishing the effective measurement procedure of L_<eq>, especially from the methodological point of view. This paper discusses the effect of the sampling period, Δ, and the sample number, N, on the L_<eq> statistics in a constant measurement time, T(=NΔ). The theoretical probability expression of general series expansion type for the average energy, E(L_<eq>=10log E/E_0, E_0=10^<-12>W/m^2), proposed here has a gamma distribution as its first expansion term and also reflects various types of linear and/or nonlinear (multi-dimensional) correlation properties for the sound power fluctuation wave into its each expansion terms. Theoretical and experimental results demonstrate the fact that a fluctuation probability distribution form of L_<eq> converges to a certain proper probability form with non-zero variance, even when N tends to infinity as Δ approaches smaller than a Nyquist period (1/2W, W: equivalent frequency bandwidth of sound power fluctuation) under the condition of a constant T. The effectiveness of the proposed theory has been confirmed experimentally too by applying it to the actual traffic noise data observed at the central area of large city.
社団法人日本音響学会の論文
1984-08-01

任意不規則変動音のL_<eq>評価量に及ぼすサンプル間隔の統計的影響(理論と実験)

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