Localization of BSR Noise Source Using the Improved 3D Intensity Method 2018-01-1530

A three-dimensional (3D) sound intensity probe is used to identify the trim components generating buzz, squeak, and rattle (BSR) noise in a vehicle interior. The 3D intensity probe has the advantages of compact overall size, small number of microphones, and low-frequency detection capability. Although the 3D sound intensimetry has been not popularly applied in practical problems due to various bias errors, a new error compensation method is adopted in this work, substantially improving the estimate’s precision. Linearization of the phase function of the cross-spectral density function between a set of two microphones is used to calculate the intensity avoiding spectral bias error, and an error map for spatial angles is used to compensate for the difference in directivity index around the microphone array. An intensity probe with an even microphone spacing of 30 mm in tetrahedral arrangement is used for the source localization. The interior space is usually a nearly dead room in terms of absorption, but the reverberation effect cannot be neglected due to the small space. Experiments are conducted by using the artificially generated and edited signals pertaining the typical characteristics of each BSR noise. Various source positions are selected, such as the instrument panel, door hinge, seat, etc., and the sound levels of the source and background are changed. The estimated bearing angles of the noise sources are analyzed on a two-dimensional plot. It is found that the localization error is generally less than 6°, which demonstrates the full possibility of using this improved 3D intensity technique for the localization of BSR noise sources in the real time.