Active attenuation system with increased dynamic range

In an acoustic system having an input for receiving an input acoustic wave and an output for radiating an output acoustic wave, active attenuation apparatus for attenuating undesirable said output acoustic wave by introducing a cancelling acoustic wave from an output transducer, comprising:

• an input transducer sensing said input acoustic wave and providing an input signal;
• an error transducer sensing the combined said output acoustic wave and said cancelling acoustic wave from said output transducer and providing an error signal;
• an adaptive filter model adaptively modeling said acoustic system on-line and having a model input from said input transducer and an error input from said error transducer and outputting a correction signal to said output transducer to introduce the cancelling acoustic wave such that said error signal approaches a given value;
• means for increasing the dynamic range of said system comprising calibration means for adjusting the amplitude of said correction signal;
• wherein said calibration means comprises digital to analog converter means operated in an analog to analog mode having an analog input from said correction signal and an analog output to said output transducer.

In an acoustic system having an input for receiving an input acoustic ware and an output for radiating anoutput acoustic wave, an active attenuation method for attenuating undesirable said output acoustic wave by introducing a cancelling acoustic wave from an output transducer, comprising:

• sensing said input acoustic wave with an input transducer and providing an input signal;
• sensing the combined said output acoustic wave and said cancelling acoustic wave from said output transducer with an error transducer and providing an error signal;
• modeling said acoustic system with an adaptive filter model having a model input from said input transducer and an error input from said error transducer and outputting a correction signal to said output transducer to introduce the cancelling acoustic wave such that said error signal approaches a given value;
• increasing the dynamic range of said modeling by adjusting the amplitude of said input signal at said model input;
• also increasing said dynamic range of said modeling by adjusting the amplitude of said error signal at said error input to said model.

In an acoustic system having an input for receiving an input acoustic wave and an output for ratiating an output acoustic wave, an active attenuation method for attenuating undesirable said output acoustic wave by introducing a cancelling acoustic wave from an output transducer, comprising:

• sensing said input acoustic wave with an input transducer and providing an input signal;
• sensing the combined said output acoustic wave and said cancelling acoustic save from said output transducer with an error transducer and providing an error signal;
• modeling said acoustic system with an adaptive filter model having a model input from said input transducer and an error input from said error transducer and outputting a correction signal to said output transducer to introduce the cancelling acoustic wave such that said error signal approaches a given value;
• increasing the dynamic range of said system by adjusting the amplitude of said correction signal;
• providing a digital to analog converter and operating it in an analog to analog mode with an analog input from said correction signal and an analog output to said output transducer.

In an acoustic system having an input for receiving an input acoustic wave and an output for radiating an output acoustic wave, active attenuation apparatus for attenuating undesirable said output acoustic wave by introducing a cancelling acoustic wave from an output transducer, comprising:

• an input transducer sensing said input acoustic wave and providing an input signal;
• an error transducer sensing the combined said output acoustic wave and said cancelling acoustic wave from said output transducer and providing an error signal;
• an adaptive filter model adaptively modeling said acoustic system on-line and having a model input from said input transducer and an error input from said error transducer and outputting a correction signal to said output transducer to introduce the cancelling acoustic wave such that said error signal approaches a given value;
• means for increasing the dynamic range of said model comprising means for sensing the amplitude of said input signal and calibration means responsive thereto for adjusting the amplitude of said input signal.