Noise controller

A noise controller which generates a cancelling sound having a phase opposite to and a sound pressure equal to those of a noise, comprising:

• an adaptive filter which inputs a standard signal based on a type of said noise, varies a filter coefficient to cancel said noise, and outputs a cancelling signal for generating said cancelling sound;
• coefficient updating means which updates the filter coefficient of the adaptive filter in order to minimize a level of an error sound remaining after the noise is cancelled by the cancelling sound;
• simulated transfer characteristics compensation means which inputs the standard signal and outputs an initial equalization signal to the coefficient updating means for simulating transfer characteristics of a transmission path between an output of the adaptive filter and an input of the coefficient updating means, the transmission path including a space in which the noise is cancelled, and which provides initial equalization for the standard signal which is input to the adaptive filter;
• a speaker which inputs the cancelling signal and generates the cancelling sound;
• a microphone which detects the error sound and generates an error signal;
• storage noise generating means for inputting and storing a noise signal output by the microphone, the microphone detecting the noise and outputting the noise signal when said cancelling sound is not generated by the speaker, and for outputting the stored noise signal as a test signal for checking said initial equalization;
• and
• initial equalization judging means which evaluates and judges an accuracy of the initial equalization signal based on a ratio of an error signal, which corresponds to the error sound remaining in said space when said stored noise signal is said cancelling signal, and a reproduced reference signal, which is obtained by synthesizing the cancelling signal output by said adaptive filter and said error signal when said stored noise signal is said standard signal.

A noise controller which generates a cancelling sound having a phase opposite to and a sound pressure equal to those of a noise, comprising:

• an adaptive filter which inputs a standard signal based on a type of said noise, varies a filter coefficient to cancel said noise, and outputs a cancelling signal for generating said cancelling sound;
• coefficient updating means which updates the filter coefficient of the adaptive filter in order to minimize a level of an error sound remaining after the noise is cancelled by the cancelling sound;
• simulated transfer characteristics compensation means which inputs the standard signal and outputs an initial equalization signal to the coefficient updating means for simulating transfer characteristics of a transmission path between an output of the adaptive filter and an input of the coefficient updating means, the transmission path including a space in which the noise is cancelled, and which provides initial equalization for the standard signal which is input to the adaptive filter;
• white noise generating means for generating a white noise signal as a test signal for checking said initial equalization;
• initial equalization judging means which evaluates and judges an accuracy of the initial equalization signal based on a ratio of an error signal, which corresponds to the error sound remaining in said space, when said white noise signal is said cancelling signal, and a reproduced reference signal, which is obtained by synthesizing the output signal of said adaptive filter and said error signal when said white noise signal is said standard signal;
• a speaker which inputs the cancelling signal and generates the cancelling sound;
• a microphone which detects the error sound and generates an error signal;
• noise level detector means for detecting a level of said error signal;
• and
• variable amplifier means, which inputs said white noise signal, for variably amplifying an output level of said white noise signal based on the detected level of said error signal.

A noise controller which generates a cancelling sound having a phase opposite to and a sound pressure equal to those of a noise infiltrating into a closed space, comprising:

• an adaptive filter which inputs a standard signal based on a type of said noise, varies a filter coefficient to cancel said noise, and outputs a cancelling signal for generating said cancelling sound;
• coefficient updating means which updates the filter coefficient of the adaptive filter based on an error sound remaining after the noise has been cancelled by the cancelling sound;
• first simulated transfer characteristics compensation means which inputs the standard signal and outputs a first initial equalization signal to the coefficient updating means for simulating transfer characteristics of a transmission path between an output of the adaptive filter and an input of the coefficient updating means, the transmission path including a space in which the noise is cancelled, and which provides first initial equalization for the standard signal which is input to the adaptive filter;
• second simulated transfer characteristics compensation means which inputs the cancelling signal output by the adaptive filter and outputs a second initial equalization signal for simulating transfer characteristics of a transmission path between an output of the adaptive filter and an input of the coefficient updating means, the transmission path including a space in which the noise is cancelled, to form a reproduced reference signal, which is obtained by synthesizing the second initial equalization signal and an error signal corresponding to the error sound, the reproduced reference signal being input to the first simulated transfer characteristics compensation means;
• initial equalization conditions change detector means for detecting a change in conditions of the closed space, said first and second simulated transfer characteristics compensation means determining the first and second initial equalizations based on the conditions of the closed space;
• and
• initial equalization judging means for judging an accuracy of the first and second initial equalizations based upon the detected change in the conditions of the closed space.