Abstract Reverberation is one of the most fundamental phenomena that describes the acoustics of an enclosure. Due to the modal behaviour of the room, the measured Schroeder decay functions may exhibit double or multiple slopes at wavelengths comparable to the dimensions of the room. In such a case the evaluation of reverberation parameters (e.g. T 20 , T 30 ) according to standardized measurement procedures [1] , [2] , [3] becomes erroneous. To overcome these shortcomings the applied filters and the analysis must take into account the modal nature of the measured response. In this work, the use of the window optimized time-frequency Stockwell transform ( S -transform) to determine the decay time and the modal frequencies from a room impulse response is investigated. The estimation of the decay time is discussed in terms of synthesized and measured decays. The applicability of the proposed method is investigated through simple examples using the Prony model. The method is also tested against noise in the signal. The measurements are carried out in a test chamber with and without an absorptive element to investigate the influence of absorption on the decay process. The simulation and experimental results show that the proposed method can be used to estimate the decay times of modes which would produce multiple sloped decays if observed in standardized frequency bands.

中文翻译：

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用于估计低频衰减时间的 Stockwell 变换

摘要 混响是描述箱体声学的最基本现象之一。由于房间的模态行为，测得的施罗德衰减函数可能在与房间尺寸相当的波长处表现出双倍或多倍斜率。在这种情况下，根据标准化测量程序[1]、[2]、[3]对混响参数（例如T 20 、T 30 ）的评估变得错误。为了克服这些缺点，应用的滤波器和分析必须考虑测量响应的模态特性。在这项工作中，研究了使用窗口优化时频 Stockwell 变换（S 变换）来确定房间脉冲响应的衰减时间和模态频率。衰减时间的估计根据合成衰减和测量衰减进行讨论。使用 Prony 模型通过简单的例子来研究所提出方法的适用性。该方法还针对信号中的噪声进行了测试。测量在带有和不带有吸收元件的测试室中进行，以研究吸收对衰减过程的影响。仿真和实验结果表明，所提出的方法可用于估计模式的衰减时间，如果在标准化频带中观察会产生多个倾斜衰减。测量在带有和不带有吸收元件的测试室中进行，以研究吸收对衰减过程的影响。仿真和实验结果表明，所提出的方法可用于估计模式的衰减时间，如果在标准化频带中观察会产生多个倾斜衰减。测量在带有和不带有吸收元件的测试室中进行，以研究吸收对衰减过程的影响。仿真和实验结果表明，所提出的方法可用于估计模式的衰减时间，如果在标准化频带中观察会产生多个倾斜衰减。