Sound Attenuation - Are You Getting What You Paid For?
Fracking has brought the natural gas compression industry closer and closer to populated areas. Control of noise pollution (i.e., sound attenuation) has become critical in designing equipment. A key source is exhaust sound from reciprocating engines. These engines require an exhaust gas silencer to attenuate the exhaust sound. Silencer manufacturers publish attenuation curves but understanding the terminology and parameters of sound attenuation can be confusing. Phrases such as critical grade and hospital grade attenuation lack standard definitions and are inconsistently used across the industry. When silencer companies do publish attenuation curves, the basis of that attenuation often varies and can make it difficult for a customer to evaluate the difference between two silencer products. The differing basis can have a significant impact on the final insertion loss of the exhaust system and meeting acoustical requirements for the site. Design approaches used by silencer companies vary; but unlike engine manufacturers who publish their engines sound power based upon an ISO standard, rarely is any standard or method specified by silencer companies. Testing protocols for large silencers can be built upon the standards found in ASTM: E477-13, E2611-09, and ISO: 7235, 11691, 15619, 3741, 3744, 3745, 3746, 9614, and 11820. There does not appear to be a standard with the NGC industry, a single ISO standard that pulls the various applicable parts of the above into one concise standard for testing industrial sized silencers in a lab environment using a computer generated sound source. Such a standard would provide a uniform means for testing and certifying of industrial silencers without acoustical labs or silencer manufacturers incurring the expense of a test engine. It would also increase the quality of the test results as test results could meet establish acoustical test grades based upon the ISO method and the testing environment used. Once established, such st