Method, apparatus and program for estimating the direction of a sound source

Sound signals received in multiple directions from a target source are accepted as inputs of multiple channels (S301), and signal of each channel is transformed into a signal on a frequency axis (S303). A phase component of the transformed signal is calculated for each of a plurality of frequencies or frequency bands (S305), and phase differences between the multiple channels are calculated (S304). An amplitude component of the transformed signal is calculated (S305), and a noise component is estimated from the calculated amplitude component (S306). An SN ratio for each frequency or frequency band is calculated on the basis of the amplitude component and the estimated noise component (S307), and frequencies or frequency bands at which the SN ratios are larger than a predetermined value are extracted (S308). Differences between arrival distances are calculated on the basis of the phase difference at each selected frequency or frequency band (S309), and the direction in which the target source lies is calculated (S311).