A signal processing apparatus comprising: a local PSD estimation unit that estimates a local power spectrum density ^φ S (ω, τ) including a power spectrum density of each of a plurality of areas |S k (ω, τ)| 2 based on an observation signal of a frequency domain obtained from a plurality of signals collected with a microphone array; and a target area/noise area PSD estimation unit that estimates a power spectrum density ^φ S (ω, τ) of at least one target area which are at least one predetermined area among the plurality of areas based on the power spectrum density of each of the at least one predetermined area included in the local power spectrum density ^φ S (ω, τ), and a power spectrum density ^φ N (ω, τ) of at least one noise area based on the power spectrum density of each of at least one area different from the at least one predetermined area included in the local power spectrum density ^φ S (ω, τ), ω being a frequency and τ being an index of a frame; characterized in that the signal processing apparatus comprises: a first component extraction unit that extracts a non-stationary component ^φ S (ω, τ) derived from a sound coming from the at least one target area and a stationary component ^φ S (ω, τ) derived from an incoherent noise from the power spectrum density ^φ S (ω, τ) of the at least one target area; a second component extraction unit that extracts a non-stationary component ^φ N (ω, τ) derived from an interference noise from the power spectrum density ^φ N (ω, τ) of the at least one noise area; and a various noise responding gain calculation unit that uses at least the non-stationary component ^φ S (ω, τ) derived from a sound coming from the at least one target area, the stationary component ^φ S (ω, τ) derived from an incoherent noise, and the non-stationary component ^φ N (ω, τ) derived from an interference noise to calculate a post-filter ∼ G(ω, τ) emphasizing the non-stationary component of the sound coming from the at least one target area. a local PSD estimation unit that estimates a local power spectrum density ^φ S (ω, τ) including a power spectrum density of each of a plurality of areas |S k (ω, τ)| 2 based on an observation signal of a frequency domain obtained from a plurality of signals collected with a microphone array; and a target area/noise area PSD estimation unit that estimates a power spectrum density ^φ S (ω, τ) of at least one target area which are at least one predetermined area among the plurality of areas based on the power spectrum density of each of the at least one predetermined area included in the local power spectrum density ^φ S (ω, τ), and a power spectrum density ^φ N (ω, τ) of at least one noise area based on the power spectrum density of each of at least one area different from the at least one predetermined area included in the local power spectrum density ^φ S (ω, τ), ω being a frequency and τ being an index of a frame; characterized in that the signal processing apparatus comprises: a first component extraction unit that extracts a non-stationary component ^φ S (ω, τ) derived from a sound coming from the at least one target area and a stationary component ^φ S (ω, τ) derived from an incoherent noise from the power spectrum density ^φ S (ω, τ) of the at least one target area; a second component extraction unit that extracts a non-stationary component ^φ N (ω, τ) derived from an interference noise from the power spectrum density ^φ N (ω, τ) of the at least one noise area; and a various noise responding gain calculation unit that uses at least the non-stationary component ^φ S (ω, τ) derived from a sound coming from the at least one target area, the stationary component ^φ S (ω, τ) derived from an incoherent noise, and the non-stationary component ^φ N (ω, τ) derived from an interference noise to calculate a post-filter ∼ G(ω, τ) emphasizing the non-stationary component of the sound coming from the at least one target area. a first component extraction unit that extracts a non-stationary component ^φ S (ω, τ) derived from a sound coming from the at least one target area and a stationary component ^φ S (ω, τ) derived from an incoherent noise from the power spectrum density ^φ S (ω, τ) of the at least one target area; a second component extraction unit that extracts a non-stationary component ^φ N (ω, τ) derived from an interference noise from the power spectrum density ^φ N (ω, τ) of the at least one noise area; and a various noise responding gain calculation unit that uses at least the non-stationary component ^φ S (ω, τ) derived from a sound coming from the at least one target area, the stationary component ^φ S (ω, τ) derived from an incoherent noise, and the non-stationary component ^φ N (ω, τ) derived from an interference noise to calculate a post-filter ∼ G(ω, τ) emphasizing the non-stationary component of the sound coming from the at least one target area.