Audio Signal Control Circuit, Audio System, and Method of Controlling Audio Signal

An audio signal control circuit includes an impedance calculator, a suppression value setter, a level detector, and a level controller. The impedance calculator is configured to calculate impedance of a speaker from voltage and current of an audio signal to be outputted to the speaker. The suppression value setter is configured to set a suppression value of the audio signal, using the impedance. The level detector is configured to perform level detection using: i) the voltage when the impedance is equal to or more than a switching threshold value, and ii) the current when the impedance is less than the switching threshold value. The level controller is configured to perform level control of the audio signal using: i) a level of a detection signal that has been detected by the level detector, and ii) the suppression value.