Use of the Reciprocity Principle for Vehicle Airborne Transfer Quantification

For understanding the differences of the sound measured in a group of cars, one needs to be able to quantify independently from the type of engine and tires, the airborne transfer from these noise sources to the passenger compartment. State of the art methods use direct measurements, which are poorly suited to modern car congested engine bays, or require engine dismantling. Arbitrary positions of source are also questionable. In the reciprocal approach, no engine dismantling is necessary. A calibrated point source is located close to the ears of a clothing manikin. The resulting acoustic pressure over the radiating surfaces is measured. The transfer functions are frequency and space averaged, and then available in third octave bands from 400Hz to 4kHz.