A signal processing apparatus comprising: an adder arranged to acquire a plurality of input signals from a plurality of microphones and calculate an added value obtained by adding the input signals together; a subtracter arranged to acquire a plurality of input signals from the plurality of microphones and calculate a subtracted value obtained by subtracting one input signal from the other input signal; a first power calculator (130a; 230a; 330a) arranged to calculate a first power by summing up squared values of the added value; a second power calculator (130b; 230b; 330b) arranged to calculate a second power by summing up squared values of the subtracted value; a determination unit arranged to determine that noise is included in the input signals when a difference between the first power and the second power is smaller than a threshold value; a gain calculator arranged to calculate a gain based on the added value and the subtracted value, wherein, when the determination unit determines that noise is included in the input signals, the gain calculator is arranged to: calculate the gain by calculating a ratio as the second power divided by the first power, and subtracting the calculated ratio from 1; when the calculated gain is greater than or equal to a predetermined gain, output the calculated gain; and when the calculated gain is smaller than the predetermined gain, output the predetermined gain; and a noise suppression unit arranged to suppress noise of the input signals by multiplying the input signals by the gain output by the gain calculator . an adder arranged to acquire a plurality of input signals from a plurality of microphones and calculate an added value obtained by adding the input signals together; a subtracter arranged to acquire a plurality of input signals from the plurality of microphones and calculate a subtracted value obtained by subtracting one input signal from the other input signal; a first power calculator (130a; 230a; 330a) arranged to calculate a first power by summing up squared values of the added value; a second power calculator (130b; 230b; 330b) arranged to calculate a second power by summing up squared values of the subtracted value; a determination unit arranged to determine that noise is included in the input signals when a difference between the first power and the second power is smaller than a threshold value; a gain calculator arranged to calculate a gain based on the added value and the subtracted value, wherein, when the determination unit determines that noise is included in the input signals, the gain calculator is arranged to: calculate the gain by calculating a ratio as the second power divided by the first power, and subtracting the calculated ratio from 1; when the calculated gain is greater than or equal to a predetermined gain, output the calculated gain; and when the calculated gain is smaller than the predetermined gain, output the predetermined gain; and calculate the gain by calculating a ratio as the second power divided by the first power, and subtracting the calculated ratio from 1; when the calculated gain is greater than or equal to a predetermined gain, output the calculated gain; and when the calculated gain is smaller than the predetermined gain, output the predetermined gain; and a noise suppression unit arranged to suppress noise of the input signals by multiplying the input signals by the gain output by the gain calculator . <EOS>