Method for delay estimation, method for echo cancellation and signal processing device utilizing the same

A signal processing device includes an echo estimation device, a captured signal buffer device and a delay estimation device. The echo estimation device is configured to generate an echo estimation signal according to a reference signal and a set of reflect path simulation coefficients and compensate for a first delay on the echo estimation signal to generate a compensated echo estimation signal. The captured signal buffer device is configured to buffer a captured signal captured by a microphone device and output the captured signal according to a second delay to generate a compensated captured signal. The delay estimation device is coupled to the echo estimation device and the captured signal buffer device and is configured to estimate an amount of delay adjustment according to the compensated echo estimation signal and the compensated captured signal and adjust the first delay or the second delay according to the amount of delay adjustment. A difference between an upper bound and a lower bound of the first