Signal processing apparatus, method, and program
View Patent ↗A signal processing technique the noise suppressing performance of which is more improved than conventional one is provided. A first component extraction unit 14 extracts a non-stationary component ^φ S (A) (ω, τ) derived from a sound coming from a target area and a stationary component ^φ S (B) (ω, τ) derived from an incoherent noise from a power spectrum density ^φ S (ω, τ) of the target area through processing of time average. A second component extraction unit 15 extracts a non-stationary component ^φ N (A) (ω, τ) derived from an interference noise and a stationary component ^φ N (B) (ω, τ) derived from an incoherent noise from a power spectrum density ^φ N (ω, τ) of a noise area.
1. A signal processing apparatus comprising:
a local PSD estimation unit that estimates each of a local power spectrum density of a predetermined target area and that of at least one noise area different from the target area based on an observation signal of a frequency domain obtained from a signal collected with M microphones forming a microphone array;
a target area/noise area PSD estimation unit that estimates a power spectrum density ^φ S (ω, τ) of the target area and a power spectrum density ^φ N (ω, τ) of the noise area based on the estimated local power spectrum density, ω being a frequency and τ being an index of a frame;
a first component extraction unit that extracts a non-stationary component ^φ S (A) (ω, τ) derived from a sound coming from the target area and a stationary component ^φ S (B) (ω, τ) derived from an incoherent noise from the power spectrum density ^φ S (ω, τ) of the target area;
a second component extraction unit that extracts a non-stationary component ^φ N (A) (ω, τ) derived from an interference noise from the power spectrum density ^φ N (ω, τ) of the noise area; and
a various noise responding gain calculation unit that uses at least the non-stationary component ^φ S (A) (ω, τ) derived from a sound coming from the target area, the stationary component ^φ S (B) (ω, τ) derived from an incoherent noise, and the non-stationary component ^φ N (A) (ω, τ) derived from an interference noise to calculate a post-filter {tilde over ( )}G(ω, τ) emphasizing the non-stationary component of the sound coming from the target area.
2. The signal processing apparatus according to claim 1 , wherein
the stationary component ^φ S (B) (ω, τ) derived from an incoherent noise is a component obtained by smoothing the power spectrum density ^φ S (ω, τ) of the target area, the non-stationary component ^φ S (A) (ω, τ) derived from a sound coming from the target area is a component obtained by removing the stationary component ^φ S (B) (ω, τ) derived from an incoherent noise from the power spectrum density ^φ S (ω, τ) of the target area, and
the non-stationary component ^φ N (A) (ω, τ) derived from an interference noise is a component obtained by removing the component obtained by smoothing the power spectrum density ^φ N (ω, τ) of the noise area from the power spectrum density ^φ N (ω, τ) of the noise area.
3. The signal processing apparatus according to claim 1 , wherein
the second component extraction unit further extracts the non-stationary component ^φ N (A) (ω, τ) derived from an interference noise from the power spectrum density ^φ N (ω, τ) of the noise area,
the first component extraction unit, with α S being a predetermined actual number, Y S being a set of indexes of frames for a predetermined interval, and β S (ω) being a predetermined actual number, calculates ^φ S (A) (ω, τ) and ^φ S (B) (ω, τ) defined by a formula below to set ^φ S (A) (ω, τ) thus calculated to the non-stationary component ^φ S (A) (ω, τ) derived from a noise coming from the target area and set ^φ S (B) (ω, τ) thus calculated to the stationary component ^φ S (B) (ω, τ) derived from an incoherent noise,
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the second component extraction unit, with α N being a predetermined actual number, Y N being a set of indexes of frames for a predetermined interval, and β N (ω) being a predetermined actual number, calculates ^φ N (A) (ω, τ) and ^φ N (B) (ω, τ) defined by a formula below to set ^φ N (A) (ω, τ) thus calculated to the non-stationary component ^φ N (A) (ω, τ) derived from an interference noise and set ^φ N (B) (ω, τ) to the stationary component ^φ N (B) (ω, τ) derived from an incoherent noise,
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the various noise responding gain calculation unit further uses the stationary component ^φ N (B) (ω, τ) derived from an incoherent noise to calculate the post-filter {tilde over ( )}G(ω, τ) emphasizing the non-stationary component of the sound coming from the target area.
4. The signal processing apparatus according to claim 1 , further comprising:
a time frequency averaging unit that performs smoothing processing in at least one of a time direction and a frequency direction with respect to the post-filter {tilde over ( )}G(ω, τ); and
a gain shaping unit that performs gain shaping with respect to the post-filter {tilde over ( )}G(ω, τ) subjected to the smoothing processing.
5. A non-transitory computer readable recording medium in which a program for causing a computer to function as each unit of the signal processing apparatus according to claim 1 is stored.
6. A signal processing method comprising:
a local PSD estimation step of estimating each of a local power spectrum density of a target area and that of at least one noise area different from the target area based on an observation signal of a frequency domain obtained from a signal collected with M microphones forming a microphone array;
a target area/noise area PSD estimation step of estimating a power spectrum density ^φ S (ω, τ) of the target area and a power spectrum density ^φ N (ω, τ) of the noise area based on the estimated local power spectrum density, ω being a frequency and τ being an index of a frame;
a first component extraction step of extracting a non-stationary component ^φ S (A) (ω, τ) derived from a sound coming from the target area and a stationary component ^φ S (B) (ω, τ) derived from an incoherent noise from the power spectrum density ^φ S (ω, τ) of the target area;
a second component extraction step of extracting a non-stationary component ^φ N (A) (ω, τ) derived from an interference noise from the power spectrum density ^φ N (ω, τ) of the noise area; and
a various noise responding gain calculation step of using at least the non-stationary component ^φ S (A) (ω, τ) derived from a sound coming from the target area, the stationary component ^φ S (B) (ω, τ) derived from an incoherent noise, and the non-stationary component ^φ N (A) (ω, τ) derived from an interference noise to calculate a post-filter {tilde over ( )}G(ω, τ) emphasizing the non-stationary component of the sound coming from the target area.