Alps Alpine Co., Ltd.

A School Corporation Kansai University

Yuji Saito

Hiroyuki Taguchi

Ryosuke Tachi

Hiroki Toita

Katsuhiko Egami

Yoshinobu Kajikawa

Tatsuya Mashiko

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.

Speaker distortion compensation device and speaker unit

In a speaker distortion correction device, an input signal passes through a nonlinear-portion correction filter and is input into a linear inverse filter. An output signal from the linear inverse filter is output into a speaker through an amplifier. For the nonlinear-portion correction filter, transfer characteristics (filter coefficients) are set that eliminate distortion due to nonlinear characteristics of the speaker. With a difference, as an error, between vibration of the speaker without distortion relative to an input signal and vibration of a vibration system of the speaker measured by a vibration measurement unit, an adaptive-algorithm execution unit performs an adaptive operation that adaptively updates filter coefficients of the linear inverse filter. When the amplitude of vibration of the vibration system of the speaker measured by the vibration measurement unit deviates from a range that normal relative to an input voltage input into the speaker, a control unit stops the adaptive operation of the adaptive-algorithm execution unit.

Speaker distortion correction device

In a first system signal processing unit, a first system auxiliary filter generates a correction signal for correcting an error signal from a noise signal, a first system subtractor subtracts the correction signal from an output of a first microphone to obtain an error signal, an adaptive filter performs an adaptive operation using the error signal to generate a cancel sound output from a first speaker, and a DMS detects a position of a user's ear. When the position of the user's ear moves, the controller stops the adaptive operation, updates the transfer function of the first system auxiliary filter to the transfer function corresponding to the noise cancel position matching the position of the user's ear, gradually changes the transfer function of the adaptive filter to the transfer function corresponding to the matching noise cancel position, and resumes the adaptive operation after the change is completed.

Growing community of inventors

Iwaki, Japan

Yuji Saito