Signal processing device

A signal processing method, comprising:

• a generation step of generating, using a generation circuit, a second signal from a first signal that is obtained by downmixing two signals;
• a mixing coefficient determination step of determining, based on a value L and a value θ, a mixing degree for mixing the first signal and the second signal and using a mixing coefficient determination circuit, the value L indicating a level ratio between the two signals, and the value θ indicating a phase difference between the two signals;
• and
• a mixing step of mixing, using a mixing circuit, the first signal and the second signal based on the mixing degree determined in the mixing coefficient determination step,
• wherein the generation step includes:
• a first filter step of generating, using a first filter circuit, a low frequency band signal in the second signal, from a low frequency band signal in the first signal;
• and
• a second filter step of generating, a second filter circuit, a high frequency band signal in the second signal, from a high frequency band signal in the first signal,
• the first filter step includes generating the low frequency band signal in the second signal by, using a delay step and an all pass filter step, (i) decorrelating a complex-number signal and (ii) adding a reverberation component to the complex-number signal, the complex-number signal being the low frequency band signal in the first signal, and
• the second filter step is different from the first filter step and includes generating the high frequency band signal in the second signal by, using an all pass filter, (i) decorrelating a real-number signal and (ii) adding a reverberation component to the real-number signal, the real-number signal being the high frequency band signal in the first signal.