Abstract: A method for operating an active noise reduction system that is designed to reduce the harmonic or sinusoidal noise emanating from a rotating device, where there is an active noise reduction system input signal that is related to the frequency of the noise to be reduced, and where the active noise reduction system comprises one or more adaptive filters that output a generally sinusoidal noise reduction signal that is used to drive one or more transducers with their outputs directed to reduce the noise. Distortions of the noise reduction signal are detected. A distortion is based at least in part on differences between the frequency of the noise reduction signal and the frequency of the harmonic noise. The noise reduction signal is altered based on the detected distortion.

Abstract: A device and method that is configured to operate an active noise reduction system for a motor vehicle, where there is an active noise reduction system input signal that is related to the vehicle engine operation, and where the active noise reduction system comprises one or more adaptive filters that output noise reduction signals that are used to drive one or more transducers with their outputs directed to reduce engine noise. The engine harmonic noise level is estimated from the input signal that is related to the vehicle engine operation, and the output of the transducers is limited based on the estimate of the engine harmonic noise level.

Abstract: A method for operating an active noise reduction system that is designed to reduce sinusoidal noise, where there is an active noise reduction system input signal that is related to the frequency of the noise to be reduced, and where the active noise reduction system comprises one or more adaptive filters that output a generally sinusoidal noise reduction signal that is used to drive one or more transducers with their outputs directed to reduce the noise. Distortions of the noise reduction signal are detected. A distortion is based at least in part on differences between the frequency of the noise reduction signal and the frequency of the sinusoidal noise. The noise reduction signal is altered based on the detected distortion.

Abstract: A method for operating an active noise reduction system that is designed to reduce the harmonic or sinusoidal noise emanating from a rotating device, where there is an active noise reduction system input signal that is related to the frequency of the noise to be reduced, and where the active noise reduction system comprises one or more adaptive filters that output a generally sinusoidal noise reduction signal that is used to drive one or more transducers with their outputs directed to reduce the noise. Distortions of the noise reduction signal are detected. A distortion is based at least in part on differences between the frequency of the noise reduction signal and the frequency of the harmonic noise. The noise reduction signal is altered based on the detected distortion.

Abstract: A system and method for reducing harmonic noise caused by two or more noise sources by causing one or more loudspeakers to produce sounds that are at about the same frequencies as the noise and of substantially opposite phase. There is a noise canceller associated with each noise source. Each noise canceller includes a harmonic sine wave generator that generates an output sine wave. Each noise canceller also has an adaptive filter that uses a sine wave to create a noise reduction signal that is used to drive one or more transducers with their outputs directed to reduce noise caused by the noise sources. There is an overlap detector that compares the harmonic frequencies and, based on their proximity, alters the operation of one or more adaptive filters.

Abstract: A system and method for reducing noise caused by two or more rotating devices by taking in input signals with frequencies that are related to the rotation rates of the rotating devices, and causing one or more loudspeakers to produce sounds that are at about the same frequencies as the noise and of substantially opposite phase. There is a noise canceller associated with each rotating device. Each noise canceller includes a harmonic frequency computer that computes a harmonic frequency and provides the harmonic frequency to a harmonic sine wave generator that generates an output sine wave. Each nose canceller also has an adaptive filter that uses a sine wave to create a noise reduction signal that is used to drive one or more transducers with their outputs directed to reduce noise caused by the rotating devices. There is an overlap detector that compares the harmonic frequencies and, based on their proximity, alters the operation of one or more adaptive filters.

Abstract: A device and method that is configured to operate an active noise reduction system for a motor vehicle, where there is an active noise reduction system input signal that is related to the vehicle engine operation, and where the active noise reduction system comprises one or more adaptive filters that output noise reduction signals that are used to drive one or more transducers with their outputs directed to reduce engine noise. The engine harmonic noise level is estimated from the input signal that is related to the vehicle engine operation, and the output of the transducers is limited based on the estimate of the engine harmonic noise level.

Abstract: A system for correcting erroneous microphone readings in a vehicle engine harmonic cancellation (EHC) system. A method for operating an engine harmonic cancelling system, includes receiving, from a first microphone at a first location in a vehicle cabin, a signal representative of noise in the vehicle cabin; receiving, from a second microphone at a second location in the vehicle cabin, a signal representative of noise in the vehicle cabin; and correlating the signal from the first microphone with the signal from the second microphone.

Abstract: A system for correcting erroneous microphone readings in a vehicle engine harmonic cancellation (EHC) system. A method for operating an engine harmonic cancelling system, includes receiving, from a first microphone at a first location in a vehicle cabin, a signal representative of noise in the vehicle cabin; receiving, from a second microphone at a second location in the vehicle cabin, a signal representative of noise in the vehicle cabin; and correlating the signal from the first microphone with the signal from the second microphone.