Problems With Using In-Vehicle Acoustic Absorption Measurements to Develop Interior Trim Parts Based on Laboratory Measurements

Setting accurate acoustic performance targets for trim components early in a vehicle program is essential to develop the vehicle on-time, with appropriate acoustical performance, at lowest weight, and at lowest cost. The laboratory measurement of acoustic absorption (ASTM C 423 and ISO 354) of flat stock trim parts is used to obtain these targets or the specific trim part is measured in a vehicle to obtain the acoustic absorption. However, the in situ measurement often does not agree with the laboratory measurement even if the variations between formed parts and flat stock materials are accounted for. A statistical energy analysis model is used to illustrate the problems with in situ absorption measurements. An approach to correct the in situ test method to obtain an approximation of the laboratory result is discussed.