EP0814456A2 - Aktives Lärm- oder Schwingungskontrollesystem und -anordnung mit verstarkten Referenzsignalen - Google Patents

Aktives Lärm- oder Schwingungskontrollesystem und -anordnung mit verstarkten Referenzsignalen Download PDF

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Publication number
EP0814456A2
EP0814456A2 EP97302679A EP97302679A EP0814456A2 EP 0814456 A2 EP0814456 A2 EP 0814456A2 EP 97302679 A EP97302679 A EP 97302679A EP 97302679 A EP97302679 A EP 97302679A EP 0814456 A2 EP0814456 A2 EP 0814456A2
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Prior art keywords
ale
adaptive
filter
signal
noise
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English (en)
French (fr)
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EP0814456A3 (de
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Steve C. Southward
Lane R. Miller
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Lord Corp
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Lord Corp
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
    • G10K11/1787—General system configurations
    • G10K11/17879—General system configurations using both a reference signal and an error signal
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
    • G10K11/1781—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions
    • G10K11/17813—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions characterised by the analysis of the acoustic paths, e.g. estimating, calibrating or testing of transfer functions or cross-terms
    • G10K11/17817—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions characterised by the analysis of the acoustic paths, e.g. estimating, calibrating or testing of transfer functions or cross-terms between the output signals and the error signals, i.e. secondary path
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
    • G10K11/1781—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions
    • G10K11/17821—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions characterised by the analysis of the input signals only
    • G10K11/17823—Reference signals, e.g. ambient acoustic environment
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
    • G10K11/1785—Methods, e.g. algorithms; Devices
    • G10K11/17853—Methods, e.g. algorithms; Devices of the filter
    • G10K11/17854—Methods, e.g. algorithms; Devices of the filter the filter being an adaptive filter
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
    • G10K11/1787—General system configurations
    • G10K11/17879—General system configurations using both a reference signal and an error signal
    • G10K11/17881—General system configurations using both a reference signal and an error signal the reference signal being an acoustic signal, e.g. recorded with a microphone
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/10—Applications
    • G10K2210/129—Vibration, e.g. instead of, or in addition to, acoustic noise
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30—Means
    • G10K2210/301—Computational
    • G10K2210/3027—Feedforward
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30—Means
    • G10K2210/301—Computational
    • G10K2210/3028—Filtering, e.g. Kalman filters or special analogue or digital filters

Definitions

  • the invention relates to the area of active noise and vibration control. Specifically, the invention relates to a feedforward active noise and vibration control system using a reference input.
  • ANVC Active noise and vibration control
  • input or reference sensors which provide signals indicative of the source of disturbance (noise or vibration)
  • error sensors which provide signals indicative of residual noise or vibration to be canceled
  • adaptive processing of the input and error signals in order to arrive at output signals.
  • These output signals drive output transducers thereby producing antinoise or antivibration with the result of reducing the residuals at the error sensors, thereby reducing the noise or vibration thereat.
  • SISO Single-Input Single-Output
  • MIMO Multi-Input Multi-Output
  • Adaptive line enhancement (ALE) methods are known for separating a signal into a periodic component signal and a random component signal.
  • ALE techniques are for canceling the maternal heartbeat in fetal electrocardiography as described in Adaptive Signal Processing, pp. 334-337, by Widrow and Stearns, 1985.
  • Another known example application of ALE techniques is for removing periodic interference from training noise in an ANVC system identification process as described in Investigations in Active Line Enhancer Techniques by Shawn Steenhagen, MS Thesis, Univ. of Wisconsin, Madison, 1993.
  • Prior Art Fig. 1 describes one conventional prior art ALE implementation.
  • the conventional Finite Impulse Response (FIR) ALE 20a processes an ALE input signal s+n, 21a, containing the periodic component signal s plus the random component signal n with the objective of separating the periodic component signal from the random component signal.
  • the ALE input signal s+n is delayed ⁇ >0 samples by the delay operator 28a to produce the delayed input signal 29a .
  • the delayed input signal is processed by an FIR filter 25a to produce an estimate s' for the periodic component signal 22a .
  • the periodic component signal estimate is subtracted from the input signal by the error summation block 24a to produce an estimate n' for the random component signal 23a .
  • One or both of these component estimates may be used depending on the requirements of the application.
  • Prior Art Fig. 2 describes a second conventional prior art ALE implementation.
  • the conventional Infinite Impulse Response (IIR) ALE 30b processes an ALE input signal s+n, 21b, containing the periodic component signal s plus the random component signal n with the objective of separating the periodic component signal from the random component signal.
  • the ALE input signal s+n is delayed ⁇ >0 samples by the delay operator 35b to produce the delayed input signal 36b .
  • the delayed input signal is processed by an FIR A-filter Ak, 31b, to produce an output 39b.
  • the estimate s' for the periodic component signal 22b is processed by an FIR B-filter Bk, 32b, to produce an output 40b .
  • the A-filter output is combined with the B-filter output in the path summation block 41b to generate the periodic component signal estimate 22b .
  • the periodic signal component estimate is given by
  • the periodic component signal estimate is subtracted from the ALE input signal by the error summation block 24b to produce an estimate n' for the broadband component signal 23b .
  • One or both of these component estimates may be used depending on the requirements of the application.
  • the ALE input signal 21b and the broadband component estimate signal n' are convolved by an A-filter correlator block 33b which is used in the LMS gradient descent method to provide A-filter adjustments 34b to the FIR A-filter 31b .
  • the periodic component signal estimate s' and the broadband component estimate signal n' are convolved by a B-filter correlator block 37b which is used in the LMS gradient descent method to provide B-filter adjustments 38b to the FIR B-filter 32b .
  • the present invention in one aspect thereof, is directed to a method and means for reducing unwanted background noise that is present in a reference (input) signal in a feedforward-type ANVC system.
  • the present invention is directed to adaptive gradient descent means for reducing the noise present in the reference (input) signal of an ANVC system.
  • an Adaptive Line Enhancer ALE is preferably placed in the input path of the ANVC system.
  • the adaptive means for enhancing the reference signal can reduce broadband noise from the input signal if there are one or more dominant tones therein to be controlled, or conversely, tones may be reduced if a broadband input is required for the input to the ANVC system.
  • the ALE may include IIR, FIR, parametric or adaptive inverse implementations, or the like.
  • the ALEs may be adaptively controlled via any of the known gradient descent algorithms.
  • the use of ALEs in the input path is beneficial to any of the known ANVC systems, including Active Noise Control (ANC), Active Structural Control (ASC), and Active Isolation Control (AIC).
  • ANC Active Noise Control
  • ASC Active Structural Control
  • AIC Active Isolation Control
  • the ALE enhanced reference signal described herein can be used with any of the known ANV control processes, such as those including FIR and IIR adaptive filters.
  • multiple ALEs may be used in parallel or cascaded relationship to provide, for example, a reference signal with contributions from multiple tones.
  • the enhanced reference signal provided by the ALE may be used as an input to auxiliary components, such as an Engine Vibration Monitor (EVM) which is used for monitoring, and/or, displaying the vibration of aircraft engines.
  • EVM Engine Vibration Monitor
  • the main advantage of the invention is that it provides a reference (input) signal to the ANVC system that has substantially higher Signal-To-Noise (SNR) ratio.
  • an ANC system 50c comprising an input sensor 52c for providing a reference signal indicative of the disturbance acoustic noise or vibration causing the disturbing acoustic noise.
  • the disturbance may be an acoustic noise emanating from a noise source, such as an aircraft engine or the like.
  • the reference signal generally will include some unwanted noise therein.
  • noise what is referred to is background noise which is uncorrelated with the disturbance which is sought to be canceled.
  • adaptive means are provided for reducing the noise present in the reference signal.
  • an Adaptive Line Enhancer (ALE) 54c which includes an adaptive filter and update means for updating the coefficients or weights of the adaptive filter, is preferably is used.
  • An error sensor 62c is provided for generating an error signal indicative of the residual acoustic noise at the point adjacent where a quiet zone is desired.
  • the means for processing the error signal and the reference signal and producing an output signal is provided in the control process 58c, in this case, ANC control, which includes a filter taking the form of a IIR or FIR filter structure with adaptive feedforward control.
  • An output transducer 60c in this case, a loudspeaker, is dynamically driven responsive to the output signal.
  • the output transducer 60c produces antinoise which preferably minimizes the noise at the point of interest to produce a quiet zone.
  • the controller 56c includes both the adaptive means, such as ALE 54c , for reducing the unwanted noise on the input signal and the control process 58c therewithin.
  • the reference enhancement means is based upon an adaptive gradient descent method and is generally implemented within the software. It should also be understood that there may be an optional filtering/conditioning step before the reference signal is provided to the ALE 54c .
  • Fig. 4 represents another ANC system 50d which is identical to the system of Fig. 3 except that the reference sensor is an accelerometer 52d .
  • One ANC system for which the ALE used within the input path as described herein may be useful is discussed in commonly assigned US Application Serial No. 08/553,227 to G. Billoud entitled “Active Noise Control System for Closed Spaces Such As Aircraft Cabins” filed Sept. 25, 1995.
  • Other ANC systems are described in US Pat. No. 4,562,589 to Warnaka et al. entitled “Active Attenuation of Noise in a Closed Structure” and US Pat. No. 4,473,906 to Warnaka et al. entitled “Active Acoustic Attenuator.”
  • Fig. 5 represents another ANVC system, and in particular, an ASC system 50e which is identical to the system of Fig. 4 except that the output transducer is an AVA 60e .
  • Active systems including AVAs are described in PCT Patent Application Serial No. PCT/US95/13610 entitled “Active Systems and Devices Including Active Vibration Absorbers (AVAs)" and US Pat. No. 4,715,559 to Fuller entitled “Apparatus and Method For Global Noise Reduction.”
  • AVAs are attached directly to the interior surface of the aircraft's fuselage and dynamically shake the fuselage wall to generate canceling noise in the aircraft's cabin.
  • Fig. 6 represents another ANVC system, and in particular, an AIC system 50f which is identical to the system of Fig. 5 except that the output transducer is an active mount 60f .
  • Active mounts are taught in commonly assigned US Pat. No. 5,174,552 to Hodgson et al. entitled “Fluid Mount with Active Control” and US Pat. App. Serial No. 08/260,945 entitled “Active Mounts for Aircraft Engines.” Further descriptions may be found in a Lord paper entitled “Frequency-Shaped Control of Active Isolators" by D. A. Hodgson. Active mounts 60f attach between an engine and the structure the engine is attached to and are dynamically actuated (driven) to control vibration therebetween or noise at a remote location.
  • Fig. 7 represents a detailed block diagram of a tonal ANVC system 50g including a reference sensor 52g , an optional band pass filter 53g , an ALE 54g , and output transducer 60g , and error sensor 62g and an adaptive control process 58g which may include system identification, hereinafter referred to as ID 42g .
  • ID 42g may be accomplished in an on-line or off-line fashion. Further, filtering or other signal conditioning is commonly used on the output signal and error signal paths, however, they are not shown for the sake of clarity in all figures described herein.
  • the ALE 54g herein includes a FIR filter structure as is described fully with reference to Fig. 1 .
  • the reference signal 51g from reference sensor 52g is preferably band-pass filtered and received at the ALE input 21g .
  • the output of the ALE 22g is provided to the control process 58g for the ANVC system 50g .
  • the ALE output 22g is comprised of the periodic component of the reference signal 51g , i.e., the one or more tones that are indicative of the noise or vibration 49g generated by the source of disturbance 48g .
  • control process 58g is achieved by an FIR filter 59g including update means, such as filtered-x LMS, or the like.
  • update means such as filtered-x LMS, or the like.
  • SISO Single-Input Single-Output
  • MIMO Multiple-Input Multiple-Output
  • the ALE output 22g is filtered through an error path model 63g (sometimes referred to as the X filter) representative of the transfer function between each output transducer 60g and error sensor 62g pair.
  • the filtered ALE output is referred to as the filtered regressor 65g .
  • Error information in line 64g represents the error signal 55g and any filtered training noise from training block 42g .
  • Error information 64g and the filtered regressor 65g are inputted to an update method and means 61g , such as Filtered-x LMS, for determining the new filter weights to be passed to the FIR control filter 59g .
  • the output 22g from the ALE 54g is filtered by the control filter 59g to arrive at the output signal 57g used to drive the output transducer 60g , e.g. a loudspeaker, AVA, active mount or the like.
  • the output signal 57g to the output transducer 60g is also cleaner and the ANVC system 50g will do a better job at cancellation of the noise or vibration.
  • Fig. 8 represents another tonal feedforward ANVC system 50h including a reference sensor 52h , an adaptive gradient descent means for reducing the uncorrelated noise present in the reference signal 51h , such as an ALE 54h , an adaptive control process 58h including an FIR filter 59h which may include system identification 42h , an output transducer 60h , and an error sensor 62h .
  • the ALE 54h used herein is fully described with reference to Fig. 2 and represents a IIR filter ALE. Again, the output 22h from the IIR ALE 54h is used as an input to the control process 58h which is identical to that described with reference to Fig. 7 .
  • Fig. 9 represents another tonal feedforward ANVC system 50j including identical elements as described with reference to Fig. 8 except that the control process 58j includes a IIR filter instead of a FIR filter. Therefore, the ANVC system 50j is a combination of a IIR control filter process 58j and a IIR ALE 54j .
  • Control process 58j may include system ID 42j which may be implemented in an on-line or off-line fashion.
  • IIR control filter structures are described in US Pat. No. 4,677,676 to Eriksson entitled "Active Attenuation System with On-Line Modeling of Speaker, Error Path, and Feedback Path" and US Pat. No. 4,677,677 to Eriksson entitled "Active Sound Attenuation System with On-Line Adaptive Feedback Cancellation.”
  • Fig. 10 is a schematic showing one embodiment of a parametric IIR ALE.
  • the adaptive filter is a IIR filter similar to the prior art Fig. 2 ; however, the parametric IIR ALE described herein does not require a delay operation as in 35b , and the filter coefficient update process is greatly simplified with a constrained adaptation process due to the parametization.
  • the parametric IIR ALE 69m processes an ALE input signal s+n, 21m, containing the periodic component signal s plus the random component signal n with the objective of separating the periodic component signal from the random component signal.
  • the ALE input signal is processed by an FIR A-filter A ( ⁇ k), 31m , to produce an output 39m .
  • the estimate s' for the periodic component signal 22m is processed by a FIR B-filter B ( ⁇ k), 32m , to produce an output 40m .
  • the A-filter output is combined with the B-filter output in the path summation block 41m to generate the periodic component signal estimate 22m .
  • the periodic component signal estimate is subtracted from the ALE input signal by the error summation block 24m to produce an estimate n' for the broadband component signal 23m .
  • One or both of these component estimates may be used depending on the requirements of the application.
  • Each of the IIR filter coefficients in A ( ⁇ k) and B ( ⁇ h) are explicitly parametized by the center frequency ⁇ k. This parametization is accomplished by first selecting a desired frequency response for the IIR filter.
  • a preferred response is a second-order band-pass filter which is given by The filter bandwidth ( BW ) and the sharpness of resonance ( Q ) are given by where ⁇ is the damping ratio, and ⁇ o is the center frequency.
  • BW filter bandwidth
  • Q sharpness of resonance
  • the three non-zero digital filter coefficients may be analytically expressed in terms of the center frequency and bandwidth. This parametization is given by where T is the sample period, and ⁇ k is the time varying center frequency. For a constant bandwidth, the digital filter coefficients are parametized by center frequency only.
  • the derivatives are also analytically available for the second-order band-pass filter response, and are given by
  • the parametric FIR filter coefficients 31m and 32m are updated with each new estimate of the center frequency 77m .
  • the center frequency is updated by the center frequency update 76m wherein the gradient estimate 75m is added to the previous center frequency value.
  • the gradient estimate is the output of a gradient summation block 74m which sums the A-filter gradient contribution 71m and the B-filter gradient contribution 73m .
  • the ALE input signal is convolved with n' in the A-filter correlator block 33m which produces an A-filter convolution vector 78m .
  • the A-filter convolution vector is multiplied by the gradient of the A-filter coefficients with respect to center frequency, in the A-filter parametric gradient product block 70m , which produces the output A-filter gradient contribution 71m .
  • the periodic component signal estimate s' is convolved with n' in the B-filter correlator block 37m which produces a B-filter convolution vector 79m .
  • the B-filter convolution vector is multiplied by the gradient of the B-filter coefficients with respect to center frequency, in the B-filter parametric gradient product block 72m , which produces the output B-filter gradient contribution 73m .
  • the parametric IIR ALE may be further simplified in several ways.
  • One improvement to the invention is to restrict the operational range of the center frequency, which is easily accomplished when the center frequency is adapted explicitly. The restriction is accomplished by not allowing the adaptation process to select a center frequency outside of some prescribed range.
  • the restriction is accomplished by not allowing the adaptation process to select a center frequency outside of some prescribed range.
  • Upon inspection of the partial derivatives of the filter coefficients with respect to center frequency it may be observed that some of the derivatives are several orders of magnitude smaller than the others. These small derivatives may be assumed zero and the corresponding parameter values may be assumed constant over the restricted frequency range.
  • the transcendental parametric expressions for the coefficients whose derivatives are not negligible may also be preferably replaced with polynomial curve fit, or other expressions which are simpler to evaluate in real time.
  • Fig. 11 is a schematic showing one embodiment for an adaptive inverse ALE.
  • the adaptive filter is an FIR filter similar to the prior art Fig. 1 ; however, the adaptive inverse ALE uses the adaptive filter coefficients in a novel way for separating the periodic component signal from the random component signal.
  • the adaptive inverse ALE, 80p processes an ALE input signal 21p where reference numerals 21p, 28p, 29p, 34p, 33p, 25p, and 24p are exactly as described in reference to Fig. 1 .
  • Signal 81p is an auxiliary periodic component signal and signal 82p is an auxiliary random component signal which are only used in the adaptation of the FIR A-filter Ak .
  • the ALE input signal is further processed by a IIR filter which is constructed from the modified FIR filter coefficients Ak , and an additional filter Gk as described below.
  • the LMS gradient descent update described above will drive the A-filter coefficients toward the optimal values given above.
  • the ALE input signal is input to a FIR feedforward filter Gk, 31p, which produces a G-filter output 83p .
  • the periodic component signal estimate 22p is produced from the path summation 41p whose inputs are the G-filter output and the modified A-filter output 84p .
  • the G-filter is a single coefficient which appropriately scales the ALE input signal.
  • the signal s' is delayed by the delay block 28p' to produce the delayed output 29p' which is input to the modified A-filter 85p .
  • the modified A-filter produces the modified A-filter output 84p .
  • the resulting digital IIR filter would have undamped poles at the frequency of the input excitation. In practice, damping is added to the poles.
  • the G-filter must generally be selected such that the resulting IIR filter has the appropriate gain at the center frequency.
  • the estimate s' for the periodic component signal 22p is subtracted from the ALE input 21p in the error summation 24p' to produce an estimate for the random component signal 23p .
  • One or both of these component estimates may be used depending on the requirements of the application.
  • One improvement to this aspect of the invention is to restrict the operational range of the center frequency, which is easily accomplished when the center frequency is adapted explicitly. The restriction is accomplished by not allowing the adaptation process to select a center frequency outside of some prescribed range. When the operating frequency range is restricted, the transcendental parametric expressions for A[1] and the G-filter coefficient may be preferably replaced with polynomial curve fit or other expressions which are simpler to evaluate in real time.
  • Fig. 12 represents another tonal feedforward ANVC system 50m including a reference sensor 52m , adaptive gradient descent means for reducing the uncorrelated noise present in the reference signal 51m , such as ALE 54m , an adaptive control process 58m including a FIR filter 59m which may include system identification 42m , an output transducer 60m, and an error sensor 62m .
  • the ALE 54m used herein receives its ALE input 21m in the form of the band-pass-filtered reference signal.
  • the ALE output 22m which represents a more refined tonal signal, as compared to the reference signal 51m and the band-pass-filtered reference signal, is provided to the control process 58m .
  • the ALE 54m is fully described with reference to Fig.
  • Fig. 13 represents another tonal feedforward ANVC system 50p identical to that described with reference to Fig. 12 except that the ALE 54p is an adaptive inverse ALE.
  • the ALE 54p used herein is fully described with reference to Fig. 11 and represents an adaptive inverse FIR ALE. It should be understood that although a FIR control process 58p is shown, a IIR control process as described with reference to Fig. 9 could also be employed in combination with the adaptive inverse ALE 54p .
  • the ALE includes its ALE input 21p and ALE output 22p within the reference path and is used to provide a refined tonal signal with the broadband uncorrelated noise reduced.
  • Fig. 14 represents a broadband feedforward ANVC system 50r including an ALE 54r .
  • the ANVC system is identical to that described with reference to Fig. 7 except that the ALE 54r is used to reduce unwanted uncorrelated periodic noise (tones) in the reference signal path and leave only the broadband noise, which is desired to be controlled. Since broadband noise is desired to be reduced by the broadband control process, then any uncorrelated tones present in the reference signal will detract from the effectiveness of the broadband control.
  • the ALE 54r used herein is fully described with reference to Fig. 1 and represents a conventional FIR ALE. It should be understood that although a FIR control process 58r and conventional FIR ALE 54r are shown, that other combinations are possible.
  • the output from the conventional IIR ALE 30b in Fig. 2 at 23b may be used as a broadband input to any ANV control such as the FIR ANV Control described with reference to Fig. 8 .
  • the broadband output from the parametric ALE 69m described in Fig. 10 may be the broadband input to an FIR control similar to that described with reference to Fig. 12 .
  • the broadband output from the adaptive inverse ALE 80p at 23p (Fig. 10) may be used as an input to an ANV control, such as the control process described with reference to Fig. 13 .
  • Fig. 15 represents a tonal feedforward ANVC system 50t including multiple ALEs 54t and 54t' providing multiple signals to the ANV control.
  • the ANVC system 50t generally represents a MIMO system for controlling multiple tones emanating from the source 58t which produce unwanted noise or vibration at a point of interest, for example within an aircraft cabin.
  • the reference sensor 52t picks up the disturbance signal containing therein the multiple tones to be controlled.
  • the signal is band-pass filtered to separate into two frequency ranges, fr1 and fr2 , the signals containing the tones of interest. For example, BPF 53t passes the lower range of frequencies and BPF 53t' passes only the upper range of frequencies.
  • the ALEs 54t and 54t' in this embodiment are IIR ALEs as described with reference to Fig. 8 and are arranged in a parallel relationship.
  • the ALEs 54t and 54t' may also be low-order IIR, FIR, parametric, or adaptive inverse ALEs. Low-order implies they each have only a low number of taps.
  • ALE 54t passes a lower frequency tone, for example, a signal indicative of the N1 engine rotation frequency of an aircraft engine to the ANV control 58t .
  • ALE 54t' passes a higher frequency tone, for example, a signal indicative of the N2 engine rotation frequency of an aircraft engine to the ANV control 58t .
  • the ANV control process 58t then drives output transducer(s) 60t responsive to the error signals from the error sensor(s) 62t to preferably cancel the unwanted tones present at the point of interest that are caused by the source 48t . It should be understood that in the tonal case, the ALEs 54t and 54t' reject the uncorrelated broadband noise within each frequency range of operation fr1 and fr2 and thereby provide an enhanced signal representative of the tones of interest to the ANV control 58t .
  • Fig. 16 represents a tonal feedforward ANVC system 50v including a high-order FIR ALE 54v providing a signal to the ANV control 58v .
  • high-order it is meant that the FIR filter therein has a high number of taps.
  • Fig. 17 represents a tonal feedforward ANVC system 50w including a pair of cascaded ALEs 54w and 54w' providing reference signals to the ANV control 58w .
  • the first ALE 54w is used to enhance only the first tone of interest, while the second tone is enhanced by the second ALE 54w' .
  • Fig. 18 represents a tonal feedforward ANVC system 50z including an ALE 54z for providing a clean signal to the ANV control 58z .
  • the output from the ALE 54z is also used as an input to an auxiliary component 90z .
  • the output from the ALE 54z may be used in an auxiliary component 90z such as an Engine Vibration Monitor (EVM) including a peak detect 92z , signal processing means 94z , and display means 96z .
  • EVM Engine Vibration Monitor
  • Fig. 19 and Fig. 20 represent the raw reference signal 51m from the reference sensor 52m and the filtered output from the BPF 53m , i.e., the ALE input 21m , and the tonal-enhanced ALE output 22m from the ALE 54m for the parametric embodiment of Fig. 12 .
  • the raw reference signal 51m provided from the reference sensor 52m is indicative of a reference signal (vibration) that is picked up by an accelerometer mounted on a jet engine.
  • the engine has multiple vibrations, for example, at N1 and N2 , which produce tonal noise within the aircraft's cabin.
  • Present in the reference signal 51m is unwanted broadband background and some periodic noise 66m .
  • the ALE input 21m represents the reference signal once it has been filtered through the band pass filter 53m .
  • the range of the band pass filter 53m is centered around the nominal of N1 and rejects broadband noise below and above its operating range.
  • the ALE 54m further enhances the input signal 21m and produces an ALE output signal 22m which is significantly more indicative of the tone of interest, in this case N1 .
  • N1 the tone of interest
  • Similar results may be obtained for the conventional FIR ALE of Fig. 1 , the conventional IIR ALE of Fig. 2 and the adaptive inverse ALE of Fig. 11 .
  • Similar results can be achieved if one desires to remove the tones and leave the broadband noise as is described with reference to Fig. 14 . This may be desirable for a system where the input is from a road wheel in a vehicle and broadband road noise is being controlled in the vehicle compartment or cabin.
  • the present invention is directed to a method and means for reducing unwanted background noise present in a reference (input) signal of a feedforward-type ANVC system.
  • an Adaptive Line Enhancer ALE
  • ALE Adaptive Line Enhancer
  • the ALE may include IIR, FIR, parametric or adaptive inverse implementations, or the like.
  • the use of ALEs in the input path is beneficial to Active Noise Control (ANC), Active Structural Control (ASC), and Active Isolation Control (AIC) systems.
  • ALEs may be used in parallel or cascaded relationship and, further, the ALE output may be used as an input to auxiliary components, such as Engine Vibration Monitors (EVMs).
  • EVMs are described in SAE paper 871732 entitled “The V-22 Vibration, Structural Life, and Engine Diagnostic System, VSLED" by M. J. Augustin and J. D. Phillips.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
  • Vibration Prevention Devices (AREA)
EP97302679A 1996-06-17 1997-04-18 Aktives Lärm- oder Schwingungskontrollesystem und -anordnung mit verstarkten Referenzsignalen Withdrawn EP0814456A3 (de)

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ES2143952A1 (es) * 1998-05-20 2000-05-16 Univ Madrid Politecnica Atenuador activo de ruido acustico mediante algoritmo adaptativo genetico.
EP1107225A2 (de) * 1999-12-01 2001-06-13 Digisonix, Llc Aktive Schalldämmungsanordnung, in welcher der Regressionsfilter von einem Gesamtsystem-Testmodel bestimmt wird
US6487524B1 (en) * 2000-06-08 2002-11-26 Bbnt Solutions Llc Methods and apparatus for designing a system using the tensor convolution block toeplitz-preconditioned conjugate gradient (TCBT-PCG) method
EP1703878A1 (de) * 2003-11-26 2006-09-27 The Regents of the University of California Aktives geräuschkontrollverfahren und gerät mit feedforward- und feedbackward-reglern
WO2010131154A1 (en) * 2009-05-11 2010-11-18 Koninklijke Philips Electronics N.V. Audio noise cancelling
CN101231846B (zh) * 2007-12-27 2011-02-02 中国农业大学 利用声波干涉方式的主动噪声控制系统及噪声控制方法
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US10885896B2 (en) 2018-05-18 2021-01-05 Bose Corporation Real-time detection of feedforward instability

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ES2143952A1 (es) * 1998-05-20 2000-05-16 Univ Madrid Politecnica Atenuador activo de ruido acustico mediante algoritmo adaptativo genetico.
EP1107225A2 (de) * 1999-12-01 2001-06-13 Digisonix, Llc Aktive Schalldämmungsanordnung, in welcher der Regressionsfilter von einem Gesamtsystem-Testmodel bestimmt wird
EP1107225A3 (de) * 1999-12-01 2003-05-02 Digisonix, Llc Aktive Schalldämmungsanordnung, in welcher der Regressionsfilter von einem Gesamtsystem-Testmodel bestimmt wird
US6487524B1 (en) * 2000-06-08 2002-11-26 Bbnt Solutions Llc Methods and apparatus for designing a system using the tensor convolution block toeplitz-preconditioned conjugate gradient (TCBT-PCG) method
EP1703878A1 (de) * 2003-11-26 2006-09-27 The Regents of the University of California Aktives geräuschkontrollverfahren und gerät mit feedforward- und feedbackward-reglern
EP1703878A4 (de) * 2003-11-26 2009-08-26 Univ California Aktives geräuschkontrollverfahren und gerät mit feedforward- und feedbackward-reglern
US7688984B2 (en) 2003-11-26 2010-03-30 The Regents Of The University Of California Active noise control method and apparatus including feedforward and feedback controllers
CN101231846B (zh) * 2007-12-27 2011-02-02 中国农业大学 利用声波干涉方式的主动噪声控制系统及噪声控制方法
US9165549B2 (en) 2009-05-11 2015-10-20 Koninklijke Philips N.V. Audio noise cancelling
WO2010131154A1 (en) * 2009-05-11 2010-11-18 Koninklijke Philips Electronics N.V. Audio noise cancelling
CN102422346A (zh) * 2009-05-11 2012-04-18 皇家飞利浦电子股份有限公司 音频噪声消除
CN101709733B (zh) * 2009-10-19 2012-09-05 大连海事大学 一种电液伺服系统实时波形再现控制方法
CN104684485A (zh) * 2012-05-11 2015-06-03 3M创新有限公司 带噪声振动控制的生物声学传感器
WO2013170018A1 (en) * 2012-05-11 2013-11-14 3M Innovative Properties Company Bioacoustic sensor with noise vibration control
US9462994B2 (en) 2012-05-11 2016-10-11 3M Innovative Properties Company Bioacoustic sensor with active noise correction
WO2017223077A1 (en) * 2016-06-20 2017-12-28 Bose Corporation Mitigation of unstable conditions in an active noise control system
US9922636B2 (en) 2016-06-20 2018-03-20 Bose Corporation Mitigation of unstable conditions in an active noise control system
CN109313889A (zh) * 2016-06-20 2019-02-05 伯斯有限公司 缓解主动噪声控制系统中的不稳定状况
JP2019519819A (ja) * 2016-06-20 2019-07-11 ボーズ・コーポレーションＢｏｓｅ Ｃｏｒｐｏｒａｔｉｏｎ 能動型ノイズ制御システムにおける不安定状態の緩和
CN109313889B (zh) * 2016-06-20 2023-10-24 伯斯有限公司 缓解主动噪声控制系统中的不稳定状况
US10885896B2 (en) 2018-05-18 2021-01-05 Bose Corporation Real-time detection of feedforward instability
US10244306B1 (en) 2018-05-24 2019-03-26 Bose Corporation Real-time detection of feedback instability

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