ランダム変動騒音下の音声明瞭度と了解度に関する基礎実験 : 変動騒音の言語聴取妨害に関する研究その1

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It is known that a sound articulation can be estimated in the presence of a steady noise. In most circumstances, however, the environmental noise consists of time-varying sources, and the speech interference of such a noise cannot easily be estimated. Several papers have appeared on this subject, but almost no study on the Japanese language can be found. In this paper the interference of time-varying noise with speech listening is described on the basis of experiments, in which the sound and syllable articulation, and sentence intelligibility are investigated by using a synthesized time-varying noise. Synthesized noise has a spectrum similar to that of road traffic noise (Fig. 2), and a change in sound level of noise is characterized in this experiment by the condition that the level fluctuations occur randomly (Fig. 1) and maintain the normal distribution as a whole (Fig. 4). Moreover a change in level occurs stepwise. Fig . 3 shows a block diagram of our experiments. 120 uttered lists for syllable articulation tests and 32 lists for sentence intelligibility tests were prepared prior to the experiments. The syllable articulation list consists of 100 syllables and the sentence intelligibility list consists of 50 easy questions respectively. Four female students with normal hearing acuity were the subjects in the articulation tests and the intelligibility tests respectively, and two of them participated in both experiments. Speech samples were presented to the subjects through the headphones at 62 dBSPL in the articulation test and 64 dBSPL in the intelligibility test. Fig. 5 and Fig. 6 show the relations between sound or syllable articulation and the duration of the step D, where noise is held constant, for some ？L's which denote the excess of long time rms level of speech over the median of sound level distribution of noise. Fig. 7 shows the relation between sentence intelligibility and D. From these figures and the results of analysis of variance, the effects of D on the articulation and the intelligibility are said to be not so great as ？L and σ, which are described below. Fig. 8 and Fig. 9 show the relations between sound or syllable articulation and the standard deviation of sound level distribution of noise (σ). As seen from the figures, the articulation score has a tendency to decrease with the increase of σ, especially for greater ？L. Fig. 10 shows the relation between sentence intelligibility and σ. The intelligibility also seems to decrease along with the increase in σ. The relation between syllable articulation and sentence intelligibility is shown in Fig. 11, and the relation between syllable articulation and sound articulation is drawn in Fig. 12. From these figures, we can say that the sentence intelligibility is more influenced by sound level fluctuation of noise than the syllable articulation, while the relation between syllable and sound articulation in the presence of time-varying noise is much the same as that for steady noise. We can say again from Fig. 11 that the score of the intelligibility corresponding to a certain score of the syllable articulation is smaller for the greater σ than for the smaller σ. In other words, the connected speech is easy to suffer losses from fluctuating noise. Since the articulation decreases with an increase in σ as seen from Figs. 8 and 9, it is worth while to investigate into the relation between those scores and the equivalent sound levels (L_<eq>) of time-varying noise. Fig. 13 denotes it. A simple relation is not found between the articulation and L_<eq> of noise. Fig. 15 shows the sound articulations estimated from the experimental articulation in the presence of steady noise (Fig. 14) and occurence probabilities of sound levels in time-varying noise. Fig. 16 and Fig. 17 show the results of syllable articulation and sentence intelligibility calculated in the same manner as in Fig. 15. It can be said from those figures that the estimated values give a
社団法人日本音響学会の論文
1978-09-01

ランダム変動騒音下の音声明瞭度と了解度に関する基礎実験 : 変動騒音の言語聴取妨害に関する研究その1

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ランダム変動騒音下の音声明瞭度と了解度に関する基礎実験 : 変動騒音の言語聴取妨害に関する研究 その1

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ランダム変動騒音下の音声明瞭度と了解度に関する基礎実験 : 変動騒音の言語聴取妨害に関する研究その1