Optimisation of an active control system to reduce the

Optimisation of an active control system to
reduce the exhaust noise radiated by a small
generator
María Cuesta* and Pedro Cobo
Instituto de Acústica. CSIC. Serrano 144, 28006 Madrid. SPAIN
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Abstract
In a previous paper [1] the authors reported a passive/active
system to control the exhaust noise radiated by a small generator.
Passive control was afforded by a steel rectangular enclosure lined
with a layer of absorbing material. The enclosure, designed to provide
the higher Insertion Loss,
supplied attenuation higher than 20 dB
above 500 Hz. To reduce the noise below 400 Hz, an active control
system was designed with one reference, one error input and one
control output. Whilst many harmonics in this frequency band were
attenuated, the ANC system was unable to reduce some of them. The
aim of this paper is to identify the origin of this lack of attenuation
and to alleviate it.
An exhaustive analysis of both the transfer
function between the secondary source and the error sensor (the
plant) and the reference signal has been carried out. A new ANC
system with improved performance is described which controls all the
harmonics until 300 Hz.
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* Corresponding author (e-mail: [email protected])