带通滤波后语音可懂度的实验研究

语音信号在空气中远距离传播时，由于大气的低通滤波效应，高频分量衰减严重，能够到达远端的量很少．其占据的信号源部分能量不能有效利用，从而使语音传播距离受到很大限制。在某些要求距离的场合，需要牺牲部分语音清晰度，传播时保留最低限度的可懂度以提升语音传播距离。语音信号中所含频率成分丰富，但对语音可懂起决定作用的只是其中有限范围的频段。以数字滤波和主观评价的方法对采样频率为44．1kHz的汉语语音可懂的极限频率进行了研究。结果表明，在满足语音内容完全可懂的要求时，汉语语音频率的最低上限应取在1kHz，最高下限应处于300Hz。该结论可以为调制信号源频率以提高能量利用效率，提升语音传播距离提供重要依据。

Experimental research on the intelligibility of bandpass speech

When speech signals propagate in the atmosphere, the high frequency components attenuate seriously for the low-pass filtering effect of atmosphere, and so cannot propagate too fax. However, propagation distance is important in some cases, it is necessary to impair the articulation but keep the liminal intelligibility for increase of propagation distance. Speech signals contain abundant frequency components. And the decisive frequencies, which make the speech intelligible, are merely limited within a narrow band. The possible frequency band based on an intelligible standard Chinese speech with a sampling rate of 44.1 kHz is investigated by using digital filtering and human subjective evaluation methods. Results show that for being wholly intelligible of the speech contents, the upper frequency limit could be down to 1 kHz, and the lower frequency could be up to 300 Hz. Based on this conclusion, the modulating frequencies of signal source can be limited within this band to increase the energy utilization efficiency, and therefore increase the propagation distance of speech.