| 摘要 |
A digital circuit arrangement for an ambient noise-reduction system affording a higher degree of noise reduction than has hitherto been possible, through the use of a low latency signal processing chain. The circuit arrangement includes analogue-to-digital converter 81, a digital processor including digital filter 82 and digital delta-sigma modulator 83, and digital-to-analogue converter 84. The arrangement converts analogue ambient noise signals into N-bit digital signals at sample rate f0, 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 f0 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, providing the ability to fine tune the group delay for feed-forward applications. |
