A digital circuit arrangement for an ambient noise-reduction system affording a higher degree of noise reduction than has hitherto been possible. The arrangement converts the analog signals into N-bit digital signals at sample rate f.sub.0, and then subjects the converted signals to digital filtering. The value of N in some embodiments is 1 but, in any event, is no greater than 8, and f.sub.0 may be 64 times the Nyquist sampling rate but, in any event, is substantially greater than the Nyquist sampling rate. This permits digital processing to be used without incurring group delay problems that rule out the use of conventional digital processing in this context. Furthermore, adjustment of the group delay can readily be achieved, in units of a fraction of a micro-second, providing the ability to fine tune the group delay for feed forward applications.

An active noise cancellation system and method, in which an active noise controller generates an anti-noise signal based on an error signal, and a loudspeaker operatively coupled to the active noise controller converts the anti-noise signal into anti-noise sound. An acoustic error sensor operatively coupled to the active noise controller picks up sound and converts the picked-up sound into the error signal. The acoustic error sensor is disposed at a front face of the loudspeaker.

A digital circuit arrangement for an ambient noise-reduction system affording a higher degree of noise reduction than has hitherto been possible. The arrangement converts the analog signals into N-bit digital signals at sample rate f.sub.0, and then subjects the converted signals to digital filtering. The value of N in some embodiments is 1 but, in any event, is no greater than 8, and f.sub.0 may be 64 times the Nyquist sampling rate but, in any event, is substantially greater than the Nyquist sampling rate. This permits digital processing to be used without incurring group delay problems that rule out the use of conventional digital processing in this context. Furthermore, adjustment of the group delay can readily be achieved, in units of a fraction of a micro-second, providing the ability to fine tune the group delay for feed forward applications.

An active noise cancellation system and method, in which an active noise controller generates an anti-noise signal based on an error signal, and a loudspeaker operatively coupled to the active noise controller converts the anti-noise signal into anti-noise sound. An acoustic error sensor operatively coupled to the active noise controller picks up sound and converts the picked-up sound into the error signal. The acoustic error sensor is disposed at a front face of the loudspeaker.

The present invention is in the field of an active sound-cancellation system, an open fluid-duct comprising such an active sound-cancellation system, such as an air duct, and an active sound-cancellation computer program comprising instructions for operating such an active sound-cancellation system. The active sound-cancellation system reduces noise significantly.

A digital circuit arrangement for an ambient noise-reduction system affording a higher degree of noise reduction than has hitherto been possible. The arrangement converts the analog signals into N-bit digital signals at sample rate f.sub.0, and then subjects the converted signals to digital filtering. The value of N in some embodiments is 1 but, in any event, is no greater than 8, and f.sub.0 may be 64 times the Nyquist sampling rate but, in any event, is substantially greater than the Nyquist sampling rate. This permits digital processing to be used without incurring group delay problems that rule out the use of conventional digital processing in this context. Furthermore, adjustment of the group delay can readily be achieved, in units of a fraction of a micro-second, providing the ability to fine tune the group delay for feed forward applications.

A digital circuit arrangement for an ambient noise-reduction system affording a higher degree of noise reduction than has hitherto been possible. The arrangement converts the analog signals into N-bit digital signals at sample rate f.sub.0, and then subjects the converted signals to digital filtering. The value of N in some embodiments is 1 but, in any event, is no greater than 8, and f.sub.0 may be 64 times the Nyquist sampling rate but, in any event, is substantially greater than the Nyquist sampling rate. This permits digital processing to be used without incurring group delay problems that rule out the use of conventional digital processing in this context. Furthermore, adjustment of the group delay can readily be achieved, in units of a fraction of a micro-second, providing the ability to fine tune the group delay for feed forward applications.

The present invention is in the field of an active sound-cancellation system, an open fluid-duct comprising such an active sound-cancellation system, such as an air duct, and an active sound-cancellation computer program comprising instructions for operating such an active sound-cancellation system. The active sound-cancellation system reduces noise significantly.