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 frequency that vary in relation to the time rate of change of engine angular rotational position in an engine operating cycle, the system comprising:

• means for sensing the engine angular rotational position in the operating cycle;
• means for deriving engine rotational speed by determining the time rate of change of the angular rotational position of the engine in the operating cycle;
• means responsive to said engine rotational speed for generating a generator output signal containing at least one sinusoidal signal component, where each sinusoidal signal component has a predetermined constant amplitude, and a frequency corresponding to the frequency of a respective sinusoidal noise component, wherein the generator output signal is derived from predetermined schedule of values based upon the sensed angular rotational position of the engine in the operating cycle;
• means for producing a control signal having a varying amplitude that is obtained from a look up table based upon the derived engine rotational speed;
• means for multiplying the generator output signal with the control signal to produce a filter input signal;
• an adaptive filter having adjustable filtering characteristics for filtering the filter input signal to produce a filter output signal;
• actuator means for generating noise canceling waves in response to the filter 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 based upon the error signal 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 speed;
• signal generating means responsive to said engine rotational speed for producing a plurality of generator output signals, where each generator output signal contains at least one sinusoidal signal component with each sinusoidal signal component having a predetermined constant amplitude and a frequency corresponding to a respective one of the sinusoidal noise components;
• means for producing a plurality of control signals each control signal having a varying amplitude determined in accordance with a respective predetermined function based upon the sensed engine rotational speed;
• means for multiplying each generator output signal with a respective one of the control signals to produce a corresponding filter input signal;
• a plurality of adaptive filters, each adaptive filter having adjustable filtering characteristics for filtering a respective one of the filter input signals to produce a corresponding filter output signal;
• summing means for adding one 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 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 having amplitudes and frequencies that vary in relation to the time rate of change of engine angular rotation position in an engine operating cycle, the system comprising;

• means for sensing the engine angular rotational position in the engine operating cycle;
• means for sensing the engine angular rotational position in the engine operating cycle;
• means for deriving engine rotational speed by determining the time rate of change of the sensed angular rotational position of the engine in the operating cycle;
• means for producing a plurality of generator output signals, where each generator output signal contains at least one sinusoidal signal component, with at least one generator output signal containing multiple sinusoidal signal components, and each sinusoidal signal component having a constant predetermined amplitude and a frequency corresponding to the frequency of a respective one of the sinusoidal noise component, and with each generator output signal being derived from respective predetermined schedule of values based upon the sensed angular rotational position of the engine in the operating cycle;
• means for producing a plurality of control signals, each control signal having a varying amplitude determined in accordance with a respective predetermined function based upon the derived rotational speed of the engine;
• means for multiplying each generator output signal with a respective one of the control signals to produce a corresponding filter input signal;
• a plurality of adaptive filters, each adaptive filter having adjustable filtering characteristics for filtering a respective one of the filter input 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 to reduce the sensed level of residual noise.