Audio processing device
The disclosure provides an audio processing device comprising a first filter and a second filter. The first filter is configured to generate a first filtered signal based on an error signal, the error signal representative of audible sound at a target space. The second filter is configured to generate a second filtered signal based on the error signal. An anti-noise signal is generated based on the first filtered signal and the second filtered signal, and the anti-noise signal is included in the error signal. The first filter is connected to the second filter in parallel.
1 . An audio processing device, comprising:
a first active noise cancellation (ANC) filter, configured to generate a first anti-noise signal by applying only a time domain filtering to a full band of an error signal during an ANC period, the error signal is representative of audible sound at a target space; and
a second ANC filter, configured to generate a second anti-noise signal by applying only the time domain filtering to the full band of the error signal during the ANC period,
wherein the first and second anti-noise signals are each simultaneously converted into an acoustic anti-noise signal to cancel environmental noise, or the first and second anti-noise signals in combination are converted into the acoustic anti-noise signal to cancel environmental noise,
wherein the acoustic anti-noise signal is included in the error signal, and wherein the first ANC filter is connected to the second ANC filter in parallel,
wherein the first ANC filter and the second ANC filter are independent of each other, and
wherein the ANC period excludes a transition period in which both the first ANC filter and the second ANC filter temporarily generate the first anti-noise signal and the second anti-noise signal prior to only one of the first ANC filter and the second ANC filter generating the corresponding one of the first anti-noise signal and the second anti-noise signal.
2 . The audio processing device according to claim 1 , further comprising:
a receiving (RX) front end, configured to convert the error signal from an analog domain to a digital domain.
3 . The audio processing device according to claim 2 , further comprising:
a mixer, configured to generate a cancelling signal associated with the acoustic anti-noise signal by combining the first anti-noise signal with the second anti-noise signal.
4 . The audio processing device according to claim 3 , further comprising:
a transmitting (TX) front end, configured to convert the cancelling signal from a digital domain to an analog domain.
5 . The audio processing device according to claim 4 , wherein the first ANC filter and the second ANC filter are coupled to the RX front end, and the first ANC filter, the second ANC filter and the RX front end define a feedback (FB) path, wherein the FB path provides the cancelling signal to the TX front end.
6 . The audio processing device according to claim 1 , wherein each of the first ANC filter and the second ANC filter is a feedback (FB) filter, or each of the first ANC filter and the second ANC filter is a feedforward (FF) filter.
7 . The audio processing device according to claim 1 , wherein the first ANC filter is one of a feedback (FB) filter and a feedforward (FF) filter, and the second ANC filter is the one of a FB filter and a FF filter, the audio processing device further comprising:
a third ANC filter, being the other of a FB filter and a FF filter.
8 . The audio processing device according to claim 1 , wherein each of the first ANC filter and the second ANC filter is a feedback (FB) filter, the audio processing device further comprising:
a third ANC filter, being a feedforward (FF) filter, configured to generate a third anti-noise signal based on a reference signal from an exterior microphone of a headphone; and
a fourth ANC filter, being a FF filter, configured to generate a fourth anti-noise signal based on the reference signal,
wherein the third ANC filter is connected to the fourth ANC filter in parallel.
9 . The audio processing device according to claim 8 , further comprising:
a receiving (RX) front end, configured to convert the error signal from an analog domain to a digital domain;
a first mixer, configured to generate an overall FB signal by combining the first anti-noise signal and the second anti-noise signal; and
a second mixer, configured to generate an overall FF signal by combining the third anti-noise signal and the fourth anti-noise signal.
10 . The audio processing device according to claim 9 , further comprising:
a third mixer, configured to generate a cancelling signal associated with the acoustic anti-noise signal by combining the overall FB signal and the overall FF signal; and
a transmitting (TX) front end, configured to convert the cancelling signal from the digital domain to the analog domain.