Abstract
The method of estimating the articulation of speech in the presence of a time-varying noise, whose sound levels are normally distributed, is studied on the basis of articulation index, and the estimated values are compared with the experimental results. If we assume that the level distribution of noise has the median L_<50>dB(A) and the standard deviation σdB(A), it is shown that the time-varying noise has an effect equivalent to steady noise of which level is larger by |a/2|σ^2 than L_<50> of the former, as far as the sound articulation is concerned. The value of the constant a is obtained as equal to -0. 112 from the experiment for steady noise. Thus the level of the steady noise equivalent to the time-varying noise is expressed as follows;L_s=L_<50>+0. 056σ^2. It is shown that this equivalent level corresponds well with the sound articulation obtained experimentally.
