Patent ID: 7760888

Claim:
A howling suppression device for suppressing howling, which occurs when amplifying a target sound collected by a first microphone through an amplification section and outputting the amplified sound as an intensified sound from a loudspeaker, the howling suppression device comprising: a first power spectrum information producing section for producing a first power spectrum according to a first acoustic signal output, as an electric signal, from the first microphone that collects a sound and converts the sound into the electric signal; second acoustic signal obtaining means for obtaining a second acoustic signal that is an electric signal of a sound including the intensified sound and not including the target sound; a second power spectrum information producing section for producing a second power spectrum according to the second acoustic signal; a learning control section for, based on the first acoustic signal and the second acoustic signal, detecting a period in which (i) the first microphone is not collecting the target sound, and (ii) the second acoustic signal is indicating the intensified sound or a reverberating sound of the intensified sound, and for outputting a control signal indicating the detected period; a ratio storing section for storing a ratio of the second power spectrum with respect to the first power spectrum; a spectrum ratio estimating section for calculating the ratio of the second power spectrum with respect to the first power spectrum when the control signal indicates the detected period, and updating the ratio stored in the ratio storing section according to a predetermined method using the calculated ratio; and a suppression filter section for (i) estimating a sound component, other than the target sound, that has been mixed in the first acoustic signal, the sound component that has been mixed in the first acoustic signal being estimated by using the first power spectrum, the second power spectrum, and the ratio stored in the ratio storing section, and (ii) suppressing the sound component in the first acoustic signal so as to output only an acoustic signal of the target sound to the amplification section.