Search Results

Large reciprocating engines produce a tonal spectrum of sound radiating from their exhaust. Even after standard reactive mufflers and after-treatment devices are added, and the target A-weighted sound level has been achieved, very audible low frequency tones can remain, and their levels are sometimes even enhanced by the exhaust system, creating potential annoyance problems in neighboring communities. This paper describes a practical design approach to such a problem and demonstrates variation in critical system parameters that affect acoustical performance. These parameters include temperature, source impedance, end impedance, flow, and pipe lengths, which are explored through practical models. The results of field measurements before and after installation of a final design are included and demonstrate a significant reduction in the sound level at the frequencies of interest.

In the design of Recreational Vehicle generators, a particular challenge arises from marketing and engineering teams' desire to ensure that their products meet “best in class” sound quality characteristics. Furthermore, it is desirable to know these characteristics in measurable engineering terms in the product design stage, preferably before prototypes are built and tested. Using a combination of product engineering knowledge and sound manipulation techniques, this paper shows how several generator sounds were produced. These new hybrid real/ synthetic sounds along with actual competitive generator sounds were then used for consumer jury tests to determine their preferences. The sounds include a target “best in class” sound based on mechanical design criteria. Since published A-weighted sound levels can be a useful marketing tool, in one study a few different sounds were presented to juries at varying levels of loudness.