This paper deals with the development of an empirical expression to determine the lower cut-off frequency of an anechoic chamber when the source volume, chamber volume, wedge height as well as the major dimensions (i.e., total distance between the source and the chamber wall) are known. The frequency obtained from the empirical expression compares well within ±3% of the lower cut-off frequency obtained from the experiments. The paper also addresses the construction details and calibration procedure of the anechoic chamber. The chamber is calibrated by verifying the inverse square law for different directions from the sound source, and the lower cut-off frequency of the chamber is found to be 315 Hz within ±0.5 dB. Further, the fan broadband noise measurements are made, inside and outside, of the anechoic chamber in order to demonstrate the echo-free nature of the chamber and the spectra clearly shows that the chamber is anechoic for a broad range of frequencies.

中文翻译：

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消声室下限截止频率的估计：一种经验方法

本文讨论了一个经验表达式的发展，以确定当源体积、暗室体积、楔形高度以及主要尺寸（即声源和暗室壁之间的总距离）时，消声室的下截止频率) 是众所周知的。从经验表达式获得的频率与从实验获得的下限截止频率的 ±3% 之内比较好。该论文还讨论了消声室的构造细节和校准程序。腔室通过验证声源不同方向的平方反比定律进行校准，发现腔室的下截止频率为 315 Hz，±0.5 dB 以内。此外，在内部和外部进行风扇宽带噪声测量，