Active control of exhaust noise using an air horn

Abstract

For the passive muffling system used for reducing noise emissions from internal combustion engine, its performance significantly degrades especially when multiple low frequency tonal components propagates together with the flow. The tonal component originates from the explosion process of the engine, and radiates as a monopole from the muffler outlet. In this study, active noise cancelation using FxLMS algorithm is proposed to reduce the exhaust engine noise. Air-horn is proposed for cancelation of the radiated noise under high temperature environment. The vibration input to the diaphragm of the air-horn allowed the active control of the frequency and phase of the generated sound. The FxLMS algorithm adopting air-horn control sound radiation was proposed to achieve cancelation of the noise from the muffler. When the air-horn reduces the noise actively, the sound radiation characteristic changes the monopole like radiation into dipole and significantly reduced the radiated sound power.