Active noise control system for attenuating engine generated noise

A system for attenuating undesirable noise generated by an internal combustion engine, wherein the undesirable noise contains at least one sinusoidal noise component having an amplitude and a frequency that vary in accordance with engine rotational speed, the system comprising:

• means for generating an input signal containing at least one sinusoidal signal component having a frequency corresponding to the frequency of a respective sinusoidal noise component;
• means for sensing engine rotational speed;
• means for sensing engine rotational acceleration;
• an adaptive filter having adjustable filtering characteristics for filtering the input signal to produce an output signal;
• actuator means for generating noise canceling waves in response to the output signal and for superimposing the generated noise canceling waves with the undesirable noise;
• means for sensing a residual noise level resulting from the superposition of the noise canceling waves and the undesirable noise and for developing an error signal representative of the residual noise level;
• and
• means for adaptively adjusting the filtering characteristics of the adaptive filter in accordance with the error signal and the sensed engine rotational speed and acceleration to reduce the sensed residual noise level.

A system for attenuating undesirable noise generated by an internal combustion engine, wherein the undesirable noise contains multiple sinusoidal noise components each having an amplitude and a frequency that vary in accordance with engine rotational speed, the system comprising:

• means for sensing engine rotational acceleration;
• signal generating means for producing a plurality of generator output signals, each generator output signal containing at least one sinusoidal signal component having a frequency corresponding to a respective one of the sinusoidal noise components;
• a plurality of adaptive filters, each adaptive filter having adjustable filtering characteristics for filtering a respective one of the generator output signals to produce a corresponding filter output signal;
• summing means for adding each filter output signal to produce an output canceling signal;
• actuator means for generating noise canceling waves in response to the output canceling signal and for superimposing the canceling waves with the undesirable noise;
• means for sensing a residual noise level resulting from the superposition of the canceling waves and the undesirable noise and for developing an error signal indicative of the residual noise level;
• and
• means for adaptively adjusting the filtering characteristics of each one of the adaptive filters in accordance with the error signal and the sensed rotational acceleration of the engine to reduce the sensed level of residual noise.

A system for attenuating undesirable noise generated by an internal combustion engine, wherein the undesirable noise contains multiple sinusoidal noise components each having an amplitude and a frequency that vary in accordance with engine rotational speed, the system comprising:

• means for sensing engine rotational speed;
• means for sensing engine rotational acceleration;
• signal generating means for producing a plurality of generator output signals, each generator output signal containing at least one sinusoidal signal component having a frequency corresponding to a respective one of the sinusoidal noise components;
• a plurality of adaptive filters, each adaptive filter having adjustable filtering characteristics for filtering a respective one of the generator output signals to produce a corresponding filter output signal;
• summing means for adding each filter output signal to produce an output canceling signal;
• actuator means for generating noise canceling waves in response to the output canceling signal and for superimposing the canceling waves with the undesirable noise;
• means for sensing a residual noise level resulting from the superposition of the canceling waves and the undesirable noise and for developing an error signal indicative of the residual noise level;
• and
• means for adaptively adjusting the filtering characteristics of each one of the adaptive filters in accordance with the error signal and the sensed rotational speed and acceleration of the engine to reduce the sensed level of residual noise.