L. J. Eriksson
DIGISONIX, Inc., 8401 Murphy Dr., Middleton, WI 53562
Over the past decade, powerful new adaptive techniques have been developed for the active control of sound and vibration. One of the areas that has received the most attention is the application of active control to enhance the performance of silencers used on ducts or pipes. Active silencing is often combined with passive silencing to create a new form of hybrid silencer. These silencers can be used as intake or discharge silencers for heating, ventilating, and air conditioning (HVAC) fans, industrial fans, rotary blowers, compressors, internal combustion engines, gas turbines, pumps, and related equipment. This paper will review the use of active control for these applications with particular emphasis on the different reasons generating the interest in active control for each application. Among the potential advantages of active control for silencers are improved low frequency performance, reduced flow restriction, and decreased size and cost. The degree to which these potential advantages can be realized in specific applications can vary considerably as well as the ultimate impact of the improvement for the end user. These issues will be discussed using a number of actual examples and implications for the future use of active control will be suggested.