Hybrid NAH

Abstract

All traditional NAH techniques are limited to handle cases where sound sources are only on one side of an array of microphones. The reality is much more complicated however. A typical example is the analysis of noise radiation from a vehicle stationed on the chassis dynamometers inside a semi-anechoic chamber. For safety and durability concerns, the surfaces of the chamber cannot be made as acoustically absorptive as they should be. Consequently, the measured acoustic pressures consist of both direct and reflected waves. Also, the dynamometer is generating its own noise, making NAH application and analysis very difficult. To date, vehicle noise is still analyzed by measuring transfer functions between a source and receiver, or by sweeping an intensity probe over a target source surface at close range. The information obtained is often isolated and valid at the measurement locations. These traditional noise diagnosis and analysis processes cannot reveal much insightful information of the root causes of noise and structural vibrations.