Target setting procedures for vehicle powerplant noise reduction

摘要

Powerplant sound pressure level (SPL) target setting is the first critical step to develop an efficient NVH strategy that guides computer aided analysis and hardware research to achieve a desired goal in the early stage of a program. Traditionally, specifications have been set by comparison of a baseline powerplant SPL average of several measurement locations with its target, but it does not cascade SPL to individual component contributions. NVH engineers usually do whatever they can to reduce SPL of individual components but without a target. This guesswork can lead to NVH targets that are not met after all hardware has been developed and tested. An effective method is proposed that can be used to break down a powerplant SPL target to individual component levels at desired frequencies quantitatively. This new method is based on the inverse square law that the reduction of sound power level equals the reduction of sound pressure level at a fixed point in a free field. The calculations presented in this article work for both powerplant upgrades and new designs. The SPL target could be test data or theoretical calculations.