There is provided a signal processing apparatus, for suppressing a noise, which includes a first calculator to obtain a phase difference between two spectrum signals in a frequency domain transformed from sound signals received by at least two microphones to estimate a sound source by the phase difference, a second calculator to obtain a value representing a target signal likelihood and to determine a sound suppressing phase difference range at each frequency, in which a sound signal is suppressed, on the basis of the target signal likelihood, and a filter. The filter generate a synchronized spectrum signal by synchronizing each frequency component of one of the two spectrum signals to each frequency component of the other of the two spectrum signals for each frequency when the phase difference is within the sound suppressing phase difference range and to generate a filtered spectrum signal.