An audio signal processing method detects a position, in a sound space, of a sound source that generates an audio signal, the sound space being divisible into a plurality of areas, and generates an initial reflected sound control signal by convolving (i) an impulse response of an initial reflected sound linked to a first area of the sound space, among the plurality of areas of the sound space, corresponding to the detected position of the sound source to (ii) the audio signal of the sound source without convolving (iii) an impulse response of an initial reflected sound linked to any of the plurality of areas of the sound space other than the first area of the sound space corresponding to the detected position of the sound source to (ii) the audio signal of the sound source.