Abstract
Previously the authors reported on a sound quality evaluation method using a dissonant combustion noise index (DCNI) that is a new objective index for the contribution of combustion noise separated from vehicle interior noise during acceleration in the time domain. The research in this paper investigates a method of applying the DCNI to combustion noise acquired in an engine acoustic test cell. Due to differences in structural response functions, the combustion noise in the engine acoustic test cell differs in its sound pressure level and frequency characteristics from the combustion noise in the vehicle interior. Consequently, the DCNI is not directly available for combustion noise in an engine acoustic test cell. Therefore, focusing on the sensitivity differences in the structural response functions of the vehicle and the engine unit, the authors created a pseudo vehicle body response filter (PBR filter) that provides acoustic simulation of a standard vehicle body's response sensitivity. The PBR filter can convert the combustion noise in the engine acoustic test cell into a simulated equivalent of combustion noise in the vehicle interior, and makes it possible to use the DCNI. The PBR filter and the DCNI were used for an actual evaluation of the combustion noise from a prototype engine, and the results successfully confirmed the validity of this method.
