Noise reduction system using finite impulse response filter that is updated by configuration of minimum phase filter for noise reduction and associated method
A noise reduction (NR) system includes a finite impulse response (FIR) filter and a filter manager circuit. The FIR filter is used to perform NR upon a filter input derived from an input signal. The filter manager circuit is used to determine a configuration of a minimum phase filter according to the input signal, and update the FIR filter by the configuration of the minimum phase filter.
1 . A noise reduction (NR) system comprising:
a finite impulse response (FIR) filter, arranged to perform NR upon a filter input derived from an input signal; and
a filter manager circuit, arranged to determine a configuration of a minimum phase filter according to the input signal, and update the FIR filter by the configuration of the minimum phase filter, wherein the filter manager circuit comprises:
an NR filter estimation circuit, arranged to estimate an NR prototype filter according to the input signal; and
a minimum phase translator circuit, arranged to approach the NR prototype filter in a minimum phase manner, wherein the configuration of the minimum phase filter is derived from an output of the minimum phase translator circuit.
2 . The NR system of claim 1 , wherein the FIR filter is a hardware filter.
3 . The NR system of claim 1 , wherein the NR prototype filter is a time-domain NR prototype filter.
4 . The NR system of claim 3 , wherein the NR filter estimation circuit comprises:
a filter bank analysis circuit, arranged to convert the input signal from a time domain to a frequency domain;
a gain calculation circuit, arranged to generate a frequency-domain NR prototype filter by estimating background noise statistics and computing weights of a plurality of frequency bands according to an output of the filter bank analysis circuit; and
a filter bank synthesis circuit, arranged to convert the frequency-domain NR prototype filter into the time-domain NR prototype filter.
5 . The NR system of claim 1 , wherein the NR prototype filter is a frequency-domain NR prototype filter.
6 . The NR system of claim 5 , wherein the NR filter estimation circuit comprises:
a filter bank analysis circuit, arranged to convert the input signal from a time domain to a frequency domain; and
a gain calculation circuit, arranged to generate the frequency-domain NR prototype filter by estimating background noise statistics and computing weights of a plurality of frequency bands according to an output of the filter bank analysis circuit; and
the filter manager circuit further comprises:
a filter bank synthesis circuit, arranged to convert the output of the minimum phase translator circuit from the frequency domain to the time domain.
7 . The NR system of claim 1 , wherein the NR system is included in a true wireless headset, a hearing aids device, a personal sound amplification product (PSAP), a wireless microphone, or a sidetone circuit.
8 . A noise reduction (NR) method, comprising:
performing, by a finite impulse response (FIR) filter, NR upon an input signal;
determining a configuration of a minimum phase filter according to the input signal; and
updating the FIR filter by the configuration of the minimum phase filter;
wherein determining the configuration of the minimum phase filter according to the input signal comprises:
estimating an NR prototype filter according to the input signal; and
deriving the configuration of the minimum phase filter for approaching the NR prototype filter in a minimum phase manner.
9 . The NR method of claim 8 , wherein the FIR filter is a hardware filter.
10 . The NR method of claim 8 , wherein the NR prototype filter is a time-domain NR prototype filter.
11 . The NR method of claim 10 , wherein estimating the NR prototype filter according to the input signal comprises:
performing filter bank analysis to convert the input signal from a time domain to a frequency domain;
generating a frequency-domain NR prototype filter by estimating background noise statistics and computing weights of a plurality of frequency bands according to an output of the filter bank analysis; and
performing filter bank synthesis to convert the frequency-domain NR prototype filter into the time-domain NR prototype filter.
12 . The NR method of claim 8 , wherein the NR prototype filter is a frequency-domain NR prototype filter.
13 . The NR method of claim 12 , wherein estimating the NR prototype filter according to the input signal comprises:
performing filter bank analysis to convert the input signal from a time domain to a frequency domain; and
generating the frequency-domain NR prototype filter by estimating background noise statistics and computing weights of a plurality of frequency bands according to an output of the filter bank analysis; and
determining the configuration of the minimum phase filter according to the input signal further comprises:
performing filter bank synthesis to convert the configuration of the minimum phase filter from the frequency domain to the time domain.
14 . The NR method of claim 8 , wherein the NR method is employed by a true wireless headset, a hearing aids device, a personal sound amplification product (PSAP), a wireless microphone, or a sidetone circuit.