Classifications

• • 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
• • 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
  • G10K11/1787—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
  • 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
  • G10K2210/3012—Algorithms
• • 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
  • G10K2210/3017—Copy, i.e. whereby an estimated transfer function in one functional block is copied to another block
• • 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
  • G10K2210/3022—Error paths
• • 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
  • G10K2210/3023—Estimation of noise, e.g. on error signals
  • G10K2210/30232—Transfer functions, e.g. impulse response
• • 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
  • G10K2210/3025—Determination of spectrum characteristics, e.g. FFT

Definitions

• the present invention relates to a method for reproducing a secondary path in an active noise reduction system, comprising a transmission path, an adaptively adjustable filter and an addition unit, wherein the adaptively adjustable filter is adjusted in response to an output signal of the addition unit, and a method for operating a active noise reduction system.
• Noise sources are increasingly perceived as an environmental impact and are considered to reduce the quality of life.
• noise reduction methods based on the principle of wave cancellation have already been proposed.
• ANC Active Noise Canceling
• the principle of Active Noise Canceling is based on the cancellation of sound waves due to interference. These interferences are generated by one or more electro-acoustic transducers, such as loudspeakers.
• the signal radiated by the electro-acoustic transducers is calculated by means of a suitable algorithm and continuously corrected.
• the basis for the calculation of the signal to be radiated by the electro-acoustic transducers are those of one or more sensors -? -
• An active noise reduction algorithm requires information from at least one sensor (for example, a microphone) that determines the residual error.
• another sensor is provided that provides information about the nature of the signal to be minimized.
• an adaptive noise reduction system requires one or more actuators (for example in the form of loudspeakers) to output the correction signal.
• the information from the sensors must be converted by an analog / digital converter into a suitable format. After processing by the algorithm, the signal is reconverted from a digital to analog converter and transmitted to the actuators.
• offline modeling of the secondary path (component influence).
• the known method for determining the secondary path is referred to as “offline modeling", since the properties of the secondary path are determined in advance, that is, while the system is not in operation.
• This method of determining the secondary path has in common the property that the time delay which occurs between the actuator and the sensor is taken into account for the calculation of the component influence (secondary path) independently of the frequency response.
• this time delay is an essential property of the secondary path, neglecting this time delay in the modeling of secondary influence affects the efficiency and stability of the whole system.
• the environmental parameters such as the air pressure or the temperature
• the duration of the signal changes. If the running time of the signal becomes smaller, the algorithm is characterized by that in the model of the secondary path given delay too slow to deliver a satisfactory result. As a result, poorer damping properties and, in extreme cases, an unstable system can arise.
• the idea with this method is to add a signal in addition to the noise that is to be canceled and to determine the properties of the secondary path (component influence) due to the change of this signal.
• the additional signal is filtered out again before the "Antinoise signal" is output via the actuator, in this case a loudspeaker.
• the disadvantage of this method is that this signal is always present.
• ANC uses a model of the secondary path (component influence)
• its properties are automatically included in the calculation of the "anti-noise”.
• the model of the secondary path contains a time delay, as is the case in the usual models, the system is limited by the fact that a change in the delay of the signal can no longer be compensated. This is especially the case when the duration of the signal decreases.
• the present invention is therefore based on the object to provide a method which does not have the disadvantages mentioned above.
• the invention firstly relates to a method for simulating a secondary path in an active noise reduction system comprising a transmission path, an adaptively adjustable filter and an addition unit, wherein the adaptively adjustable filter is set in dependence on an output signal of the addition unit.
• the method according to the invention comprises the following steps:
• a known signal is supplied to the transmission link and to the adaptively adjustable filter having an adjustable transfer function
• the adaptive filter or its transfer function is set in such a way that the output signal of the addition unit is minimal;
• a delay time of a signal through the transmission path is or is eliminated in the transfer function of the adaptively adjustable filter to produce the replica of the secondary path.
• the delay time is determined, for which purpose a method based on the peak search method is used in particular.
• a method based on the peak search method is used in particular.
• the adaptively adjustable filter operates in the frequency domain.
• white noise is supplied as a known signal to the transmission path and to the adaptively adjustable filter.
• the known signal is transformed by means of a transformation from a time domain to a frequency domain before the known signal is fed to the adaptively adjustable filter, and that an output signal of the transmission path is transformed by means of a transformation from the time domain. in the frequency domain is transformed before the output signal of the transmission path of the addition unit is supplied.
• the adaptively adjustable filter is supplied with a known signal having a constant amplitude spectrum, and that an output signal of the transmission path is transformed by means of a transformation from the time domain to the frequency domain before the output signal of the Transmission line of the addition unit is supplied.
• the phase spectrum of the known signal is no longer used. This achieves a further simplification.
• a method for operating an active noise reduction system comprising a transmission path, an adaptively adjustable filter and an addition unit, wherein the adaptively adjustable filter is adjusted in response to an output signal of the addition unit and wherein a simulated secondary-path acts on the adaptive filter such that secondary-path influences are taken into account, wherein the replica of the secondary-path has been carried out according to the method described above.
• the present invention is based on
• FIG. 1 is a simplified block diagram of a known method for determining the secondary path according to the "Offline Modeling" method
• Fig. 2 is a simplified block diagram of a
• FIG. 3 is another simplified block diagram of a known method for determining the properties of the secondary path
• Fig. 5 is a further simplified representation of
• FIG. 6 shows a further simplified block diagram of a method according to the invention, _. , _ . , _ "_
• Fig. 7 is a block diagram of another
• Fig. 8 shows an example of a waveform
• Fig. 9 shows another example of a waveform.
• Fig. 1 consists of a noise generator unit 1, the transmission path 2 with the transfer function H (z) whose properties are to be replicated, and a filter 3 in which a model H (z) of the actual transfer function H (z) is included and is controlled by an adaptive unit 4, in which an adaptive algorithm is processed.
• the model H (z) is thus the replica of the transfer function H (z) in the transmission path 2.
• the transmission path 2, the filter 3 and the adaptive unit 4 are supplied with a randomly generated by the noise generator unit 1 signal (Random Noise Generator). From the signals d (n), y (n) resulting at the output of the transmission path 2 and the filter 3, a sum is formed in an addition unit 5, wherein the output signal y (n) of the filter 3 is inverted before the addition.
• the noise generator unit 1 signal Random Noise Generator
• the resulting residual signal e (n) 6 is supplied to the adaptive unit 4.
• the one in the adaptive unit 4 processed algorithm sets the filter 3 so that the residual signal e (n) is minimized.
• An optimal adjustment of the overall system is achieved when the residual signal e (n) 6 is equal to zero. In this case, the transfer function H (z) coincides with the model H (z).
• a transmission path is formed of an amplification unit 8, an actuator 9 (for example a loudspeaker), a sensor 10 (for example a microphone) and a sensor amplifier 11.
• a noise generator unit 7 supplies this transmission path, the filter 13 and the white noise adaptive unit 15.
• the filter 13 is adjusted by the adaptive algorithm, which is executed in the adaptive unit 15, so that the result of the addition unit 14 is minimized, wherein one of the two summands must be inverted.
• time delays attributed to the secondary path (component influence) flow into the calculation of the filter 13.
• the secondary path (component influence) here consists of the specific influence of the amplifiers 8, 11, the actuator 9, the sensor 10 and the transmission medium between the actuator 9 and the sensor 10.
• a secondary path can be.
• a speaker and a microphone other actuators and sensors may be used.
• the microphone amplifier 11 may also include a filter under certain circumstances.
• the present invention consists in the fact that the influence of the signal propagation times occurring in the secondary path is canceled out by the fact that the signals are transformed from the time domain into the frequency domain. This will be illustrated with reference to the embodiment of the invention shown in FIG.
• the noise generator unit 7 supplies the secondary path with white noise.
• the noise is supplied to a transformation unit 12, which carries out a transformation from the time domain to the frequency domain.
• Another transformation unit 16 transforms the signal into the frequency domain at the end of the secondary path.
• the adaptive algorithm used in the unit 15 adjusts the filter 13 so that the sum formed in the adding unit 14 is minimized, inverting the signal resulting from the filter 13 before the summation.
• the temporal change of the maturity is excluded by a majority. It has been found that certain signal components, which are offset by a multiple of 2 * ⁇ , can not be excluded.
• the filter 13 thus only represents the properties of the secondary path (component influence) in the frequency domain.
• the difference from the method shown in FIG. 3 is the transformations carried out in the transformation units 12 and 16 from the time domain to the frequency domain.
• FIG. 8 A further embodiment variant of the method according to the invention is explained with reference to FIG. 8, with which the time delay T can be determined.
• the time delay T required for the suppression is determined.
• the component contained in the impulse response H (t) which occurs before a first maximum 31 of the impulse response H (t) is erased, for example by means of a known peak search method, by a certain number in the information contained in the impulse response Samples are looked back.
• a curve as shown in FIG. 9 is obtained.
• Fig. 4 shows the frequency spectrum of white noise. On the abscissa the frequency is 20, on the ordinate the amplitude 19 is plotted. The spectrum shows a constant course of the amplitude 17.
• Fig. 5 shows the frequency spectrum after the white noise according to Fig. 4 has passed the secondary path.
• the abscissa again has the frequency 20, and the ordinate the amplitude 19.
• the spectrum no longer shows a constant amplitude spectrum but a frequency spectrum that varies with the frequency.
• This amplitude spectrum shows a possible output signal in the frequency range of a secondary path, after it has been excited with the course of FIG.
• the amplitude 18 is no longer the same size at each frequency, as shown in FIG. 5 can be seen.
• Fig. 6 shows a block diagram, with the two noise generators 21 and 22, in which white noise is generated.
• a constant value is used at the input of the filter 13 and at the adaptive unit 15.
• the use of a number - in this case a constant value instead of a complex one Signals - is another simplification in the modeling of the secondary path.
• a simple ANC system is shown.
• the operation of an ANC system whose secondary path has been determined in the frequency domain is explained below.
• Blocks 25 and 26 deserve special attention.
• the secondary path (component influence) is identified, and at 26 an estimate of the secondary path (component influence) is indicated.
• the parameters are stored which were previously determined by means of the methods described in FIGS. 2 and 3.
• the parameters determined in the filter 13 must first be transformed back into the time domain from the frequency domain by means of an inverse transformation, before they are stored in the model of the secondary path (block 26).
• the block 26 thus describes the frequency characteristics of the secondary path 25.
• a sum is formed after the signal x (n) to be minimized has been influenced on the one hand by the transmission path 23, and on the other hand by the filter 24 and the secondary Path 25 was edited.
• the adaptive unit 27 in which an adaptive algorithm is executed, controls the filter 24 such that the residual signal e (n) 29 is as small as possible, ie minimal.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Multimedia (AREA)
• Soundproofing, Sound Blocking, And Sound Damping (AREA)
• Filters That Use Time-Delay Elements (AREA)

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• 2006
  • 2006-04-21 JP JP2008506901A patent/JP2008538420A/ja active Pending
  • 2006-04-21 WO PCT/CH2006/000219 patent/WO2006111039A1/de active Application Filing
  • 2006-04-21 KR KR1020077027123A patent/KR20080003914A/ko not_active Application Discontinuation
  • 2006-04-21 CN CNA2006800221493A patent/CN101203905A/zh active Pending
  • 2006-04-21 US US11/912,197 patent/US20080317256A1/en not_active Abandoned
  • 2006-04-21 EP EP06721921A patent/EP1872360A1/de active Pending

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