Alps Alpine Co., Ltd.

Katsuhiko Egami

Yuji Saito

Hiroyuki Taguchi

Hiroki Toita

In implementations of an audio system, when overheating of a speaker is detected, a controller controls first and second selectors to input an audio signal output by an audio source device to a cooling processing section and cause output of the cooling processing section to be output to the speaker. In the cooling processing section, a mixer mixes an audio signal obtained by removing a low-frequency component from the input audio signal by a high-pass filter with a cooling signal at an infrasonic frequency generated by a cooling signal generator and adjusted with a gain by a gain adjuster. An audio signal obtained by mixing the audio signal with the cooling signal is output from the cooling processing section via a nonlinear inverse filter. A gain setting section sets the gain such that power of the cooling signal matches power of the low-frequency component extracted by a low-pass filter.

Audio system

A speaker has a magnetic angle sensor that detects the displacement of the vibration system of the speaker. A non-linearity compensation filter compensates for output distortion due to a non-linear parameter of the speaker. A transfer function of a linear inverse filter is applied so that output distortion is eliminated from the displacement, detected by the magnetic angle sensor, of the vibration system. A controller drives the speaker by using a test signal, and measures a response from the detected displacement of the vibration system. If error between the measured response and the theoretical value, theoretically determined from the design specifications, of the response is small, the controller uses the theoretical value, theoretically determined from the design specifications, of the non-linear parameter as an active non-linear parameter and sets, in the non-linearity compensation filter, a transfer function that compensates for distortion in an output due to the active non-linear parameter.

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Fukushima, Japan

Katsuhiko Egami