Mixer with adaptive post-filtering
View Patent ↗A noise reduction system includes multiple transducers that generate time domain signals. A transforming device transforms the time domain signals into frequency domain signals. A signal mixing device mixes the frequency domain signals according to a mixing ratio. Frequency domain signals are rotated in phase to generate phase rotated signals. A post-processing device attenuates portions of the output based on coherency levels of the signals.
1. A noise reduction system, comprising:
means to mix a plurality of input signals according to a mixing ratio;
the means to mix constructively adds the plurality of input signals in response to the mixing ratio to generate an output; and
a processor configured to process portions of the output based on coherence levels of the plurality of input signals,
where the mixing ratio is based on a magnitude and a signal-to-noise ratio of the signals.
2. The noise reduction system of claim 1 where the means to mix is further configured to estimate phase differences between the plurality of input signals.
3. The noise reduction system of claim 1 where the mixing ratio comprises a ratio based on attributes of the input signals.
4. The noise reduction system of claim 3 where the mixing ratio is a time smoothed ratio.
5. The noise reduction system of claim 4 where the time smoothed ratio is a variable ratio.
6. The noise reduction system of claim 4 further comprising a wind buffet detection device configured to identify noises associated with wind flow.
7. The noise reduction system of claim 6 further comprising a wind buffet suppression device configured to dampen the identified noises associated with wind flow.
8. The noise reduction system of claim 1 , where the magnitude is an approximated magnitude and the signal-to-noise ratio is an estimated signal-to-noise ratio.
9. A noise reduction system comprising:
a signal mixing device configured to mix input signals according to a mixing ratio;
the signal mixing device constructively adds the input signals to generate an output; and
a post-processing device configured to attenuate portions of the output based on coherence levels of the input signals,
where the mixing ratio is based on a magnitude and a signal-to-noise ratio of the signals.
10. The noise reduction system of claim 9 further comprising a plurality of transducers that convert the input signals into analog or digital signals.
11. The noise reduction system of claim 9 where the signal mixing device comprises a comparator that compares the magnitude of the input signals to a noise estimate.
12. The noise reduction system of claim 9 where the signal mixing device is further configured to estimate phase differences between the input signals.
13. The noise reduction system of claim 9 where the mixing ratio comprises a ratio based on attributes of the input signals.
14. The noise reduction system of claim 13 where the mixing ratio is a time smoothed ratio.
15. The noise reduction system of claim 14 where the time smoothed ratio is a variable ratio that varies with the attributes of the input signals.
16. The noise reduction system of claim 14 further comprising a wind buffet detection device configured to identify noises associated with wind flow.
17. The noise reduction system of claim 16 further comprising a wind buffet suppression device configured to dampen the identified noises associated with wind flow.
18. The noise reduction system of claim 9 where the post-processing device attenuates portions of the output based on a user programmed element.
19. The noise reduction system of claim 9 where the post-processing device comprises a coherence edge enhancement device.
20. The noise reduction system of claim 19 where the post-processing device attenuates spectral coherence between neighboring harmonics.
21. The noise reduction system of claim 9 where the coherence levels comprise a normalized coherence that accounts for maximum and minimum coherence.
22. The noise reduction system of claim 9 where the signal mixing device comprises an echo cancellation system.
23. The noise reduction system of claim 9 where the signal mixing device and post-processing device interfaces a vehicle.
24. The noise reduction system of claim 9 , where the magnitude is an approximated magnitude and the signal-to-noise ratio is an estimated signal-to-noise ratio.