Instrumentation Requirements for Using Multiple Coherence to Enhance Vehicle Sound Detection During Electric Vehicle Minimum Noise Testing

It is difficult for pedestrians to detect an approaching electric vehicle, so the National Highway Traffic Safety Administration issued Federal Motor Vehicle Safety Standard (FMVSS) No. 141, "Minimum Sound Requirements for Hybrid and Electric Vehicles" to address safety concerns. Automobile manufacturers would like to use their existing outdoor pass-by noise test facilities and resources to perform the electric vehicle minimum noise testing described in FMVSS No. 141. However, background noise levels at their test facilities are often too high. To facilitate outdoor testing, various mathematical signal processing techniques are being investigated to improve the detection of the vehicle sound signal in the presence of normal background noise. While these signal processing techniques may not be formally authorized for vehicle certification per the FMVSS standard, the processed test results could still be used effectively for vehicle development testing. In a previous study, multiple coherence was used to improve the detection of the vehicle sound signal. The current work specifically addresses the instrumentation required for this purpose. The optimal number, type, and location of sensors is presented, along with a description of the multiple coherence approach.