In-situ noise level mapping for vehicle floor carpet

Noise level mapping of test vehicles' floor carpets was undertaken for three frequency bands, that is, low-(<500 Hz), middle- (500-2,000 Hz) and high-frequency regions (> 2,000 Hz) to compare noise control treatment performance and effectiveness. On-road tests including idling conditions and constant speed tests of 40, 60 and 80 kph were undertaken. Noise level contour maps indicate that the luxury class test vehicle is most affected by very low-frequency noise but exhibit superior performance in the middle- and highfrequency ranges. The other two test cars are vulnerable to middle- and high-frequency noise incursion at moderately high levels. Through comparison of transmission loss measurements, using an impedance tube, critical carpet sections were identified for further noise control treatment on each carpet. Sound pressure level measurements from driver's ear level location indicate that the luxury class test vehicle has the superior in-cabin acoustic package.