Noise cancellation system for vehicle exhaust includes microphone connected to computer generating anti-noise for application to compensating loudspeaker

摘要

The system uses a loudspeaker mounted within the exhaust pipe. The anti-noise system for a vehicle exhaust comprises a microphone (2) detecting the residual noise produced by the exhaust connected to an anti-noise computer (3). This delivers an anti-noise signal to an electro-acoustic transducer which is situated within the exhaust pipe. The computer is arranged to deliver an anti-noise signal (4) modulated in pulse width and applied to an controlled semiconductor switch (6). This is connected to the primary of a voltage raising transformer (7) which is connected to the vehicle electrical supply. The secondary of the transformer is connected via a filtering circuit (8) to the transducer (5).