This paper presents design and control of active mufflers used in engine exhaust systems.
Boundary element method is employed to investigate noise attenuation performances of various active
muffler structures. Based on these performance evaluations, an active muffler having only one
loudspeaker inclined at 45 degree with the muffler centerline is constructed and tested for active noise
control (ANC). The feedback ANC with two controller tuning algorithms, the filtered-x least mean
square (FXLMS) algorithm and Godart modified algorithm, is applied independently for engine
exhaust noise attenuation. Experimental investigation reveals that feedback ANC with FXLMS
algorithm can attain an averaged 23.6 dB noise attenuation for pure tone excitation and over 6 dB noise
reduction for motorcycle and automobile exhaust noises. It is also shown that feedback ANC with
Godart modified algorithm has faster transient response compared to FXLMS algorithm for a pure tone
noise, but has inferior noise attenuation capability than the FXLMS algorithm for the engine exhaust
noise at fixed speeds (about 5 dB noise reduction) as well as during run-up tests.