Bistafa S R, Bradley J S
Institute for Research in Construction-Acoustics, National Research Council, Ottawa, Canada.
J Acoust Soc Am. 2001 Apr;109(4):1474-82. doi: 10.1121/1.1354199.
By systematically varying the amount of sound absorption, and the location of the sound-absorbing material in a simulated classroom, it was possible to assess the accuracy of the prediction of speech metrics in quite simple acoustical environments. Predictions of speech level, early-to-late sound ratios (C50) and speech transmission index (STI) values were obtained analytically and with two hybrid ray-based computer programs, RAYNOISE 3.0 and ODEON 4.1. The RAYNOISE predictions were accomplished with a purely specular reflection model and also with a calibrated diffuse reflection model. ODEON uses a parameter called transition order, TO, to change the reflection procedure from purely specular to diffuse for reflections that have orders higher than TO. A parametric study was conducted to determine the best transition order for the ODEON prediction of speech metrics. It was found that the analytical predictions of speech level and C50 were on average accurate to about 1 just-noticeable difference (jnd), whereas the analytical predictions of STI were on average within 2 jnd's. ODEON predictions of speech level, C50 and STI were on average within 2 jnd's. RAYNOISE predictions of C50 and STI with the specular model were on average within 2 jnd's. However, the RAYNOISE predictions of speech level, with both types of reflection models, and the RAYNOISE predictions of C50 and STI with the diffuse model had average errors greater than 2 jnd's. The effects of the sound-absorption treatments on the measured speech metric values are also discussed.
通过系统地改变吸声量以及在模拟教室中吸声材料的位置，可以在相当简单的声学环境中评估语音指标预测的准确性。语音电平、早期与晚期声比（C50）以及语音传输指数（STI）值的预测通过解析方法以及两个基于射线的混合计算机程序RAYNOISE 3.0和ODEON 4.1获得。RAYNOISE的预测是使用纯镜面反射模型以及经过校准的扩散反射模型完成的。ODEON使用一个名为过渡阶数（TO）的参数，对于阶数高于TO的反射，将反射过程从纯镜面反射改变为扩散反射。进行了一项参数研究，以确定ODEON预测语音指标的最佳过渡阶数。结果发现，语音电平与C50的解析预测平均精确到约1个刚可察觉差（jnd），而STI的解析预测平均在2个jnd以内。ODEON对语音电平、C50和STI的预测平均在2个jnd以内。RAYNOISE使用镜面模型对C50和STI的预测平均在2个jnd以内。然而，RAYNOISE使用两种反射模型对语音电平的预测以及RAYNOISE使用扩散模型对C50和STI的预测平均误差大于2个jnd。还讨论了吸声处理对测量的语音指标值的影响。
