Design and Performance Analysis of Low Cost Acoustic Chamber for Electric Machines

This paper discusses the design and performance analysis of low-cost acoustic chamber for measurement of acoustic noise and vibration of electric machines. The purpose of this paper is to find the parameters that allow the characterization of acoustic chamber thereby making an attempt in deriving and obtaining the data of acoustic chamber. The parameters that are being calculated are acoustic transfer function, reverberation time, sound power level and cut-off frequency of acoustic chamber. To obtain the transfer function of acoustic chamber, a pair of microphones and amplifier as a source of sound have been used. Based on the results of transfer functions obtained between the pair of microphones, the cut-off frequency of acoustic chamber is determined and validated through Inverse Square Law. Noise measurements are conducted in both an ordinary environment (laboratory) and acoustic chamber. The acoustic chamber provides the free-field conditions, which satisfy the standard parameters required for the design and test for acoustic chamber. The results obtained both in an ordinary environment and acoustic chamber are compared to produce useful practical information about the noise level change caused by sound fields. The results obtained are found to be helpful in understanding the physical features and characteristics of acoustic chamber.