Vehicle active noise reduction method, device, and storage medium

Abstract

The present invention discloses a method and apparatus for active noise reduction in a vehicle. The active noise reduction method includes the steps of: generating a reference signal based on a target noise to be reduced, generating a control signal to be fed back to a sound reproduction device, filtering the reference signal, estimating a noise signal based on an error signal, and updating auxiliary control parameters, updating the error signal based on the filtered reference signal, the noise signal, and the auxiliary control parameters, and updating the control parameters based on the updated error signal and the auxiliary control parameters. The present invention can reduce noise pollution inside a vehicle and has a fast convergence speed.

Description

[Technical field]

[0001] This application claims priority to a Chinese patent application filed on December 31, 2021, application number CNCN2021116831221.

[0002] The present invention relates to the field of automobile noise control, and more particularly to a method and device for active noise reduction in a vehicle, and a storage medium. [Background technology]

[0003] With the development of modern industry, the problem of noise pollution has attracted more and more people's attention, and high-intensity noise signals also affect the comfort of listeners. Due to the sound masking effect, the volume needs to be increased to achieve a higher signal-to-noise ratio and a clearer listening effect. The long-term high sound pressure caused by this will cause irreparable damage to hearing. As the vehicle becomes more intelligent, drivers and passengers have increasingly strict requirements for the acoustic environment inside the car. Noise inside the car reduces the comfort of the driver and passengers, causes irritation and fatigue of passengers inside the car, affects the clarity of AC conversations, and even affects the driver's perception of signal sounds outside the car, increasing the traffic list. NVH (Noise, Vibration, Harshness) of automobiles is an important issue that automobile manufacturers are concerned about. Methods of reducing noise by changing the structural design, adding vibration-damping materials, using devices such as shock absorber springs, etc. are collectively called passive noise control, which can achieve relatively good noise reduction effects for medium and high frequency noise. However, this method has a relatively poor effect on low frequencies, especially the engine noise in the cabin is often concentrated at low frequencies. In addition, passive noise control requires a long adjustment time and is difficult to control costs. The active noise reduction method uses the car audio system to build an inverse signal of the noise signal, and forms a secondary sound wave to offset the noise in the target area, reducing noise pollution and improving subjective listening comfort, but adds little additional weight to the car, contributes to reducing exhaust gas, and is an environmentally friendly and energy-saving solution.

[0004] The LMS algorithm is a traditional solution for car active noise reduction, but its convergence speed is slow. Then, a momentum-based FxLMS (Filtered-x, Least Mean Square) algorithm is presented, in which a moment term is added to the traditional LMS algorithm by increasing the weight coefficient. The momentum-based FxLMS algorithm improves the convergence speed of the traditional LMS algorithm, but the convergence speed of this method is still slow. Summary of the Invention [Problem to be solved by the invention]

[0005] SUMMARY OF THE PRESENTLY PREFERRED EMBODIMENTS An object of the present invention is to provide an active noise reduction method for a vehicle, which can perform active noise reduction for the noise of a vehicle engine, reduce interior noise pollution, and has a fast convergence speed.

[0006] Another object of the present invention is to provide a vehicle active noise reduction device using the above active noise reduction method.

[0007] A third object of the present invention is to provide a computer-readable storage medium storing a program capable of implementing the above-mentioned active noise reduction method. [Means for solving the problem]

[0008] The first aspect of the present invention is Angular frequency ω of the target noise to be reduced 0 Based on two reference signals x 1 (n) and x 2 Step S1 of generating (n), where n represents a time; A step S2 of generating a control signal y(n) according to the following formula (1) and feeding it back to the sound reproducing device,

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[0009] In this specification, the reference signal is the angular frequency ω of the target noise to be reduced based on the rotation speed of the vehicle engine in actual physics. 0 e(n) refers to the harmonic signal generated by calculating e(n), where the control signal is amplified by a power amplifier device and then sent to a sound reproduction device (e.g., a voice coil of a speaker) to perform electro-acoustic conversion and form a secondary sound wave to cancel noise, and e(n) represents the error signal in the sense of signal processing, which is actually a signal collected by a sound collection device (e.g., a microphone) in the noise reduction area within the compartment in physical terms.

[0010] "Filter length" refers to the number of filtering times, where it is the zero point number of the filter. The higher the number of filtering times, the higher the frequency resolution, the higher the accuracy and the better the effect.

[0011] In one embodiment, in step S1, two reference signals x are calculated according to a function method. 1 (n) and x 2(n) are generated and shown in the following formulas. x 1 (n)=sin(ω 0 n) x 2 (n)=cos(ω 0 n)

[0012] In one embodiment, in step S2, the sound reproduction device is a car speaker.

[0013] In one embodiment, in step S4, the error signal e(n) is collected and acquired by a microphone.

[0014] In this specification, the target noise to be reduced is the noise from the vehicle engine. The above-mentioned car speaker is disposed in the vehicle compartment or at least radiates sound to the vehicle compartment, including but not limited to headrest speaker, ceiling speaker, door panel speaker, etc., and the above-mentioned microphone is disposed in the vehicle compartment or at least can collect sound signals in the vehicle compartment.

[0015] A second aspect of the present invention provides an active noise reduction device comprising a memory, a processor, and a computer program stored in the memory and executable by the processor, the computer program implementing the active noise reduction method described above when the processor executes the program.

[0016] In one embodiment, the active noise reduction device further comprises a sound reproducer for performing electro-acoustic conversion based on the control signal y(n).

[0017] In one embodiment, the sound reproduction device comprises a car speaker, which is located within or at least radiates sound into the vehicle compartment, including, but not limited to, headrest speakers, ceiling speakers, door panel speakers, etc.

[0018] In one embodiment, the active noise reduction device further comprises a microphone for collecting the error signal, the microphone being located within a vehicle compartment or at least capable of collecting audio signals within the vehicle compartment.

[0019] In a third aspect of the present invention, there is provided a computer readable storage medium having a computer program stored thereon which, when executed by a processor, implements the active noise reduction method as described above. Effect of the Invention

[0020] With the above solution, the present invention has the following advantages over the prior art: In the vehicle active noise reduction method for vehicle engine noise of the present invention, in updating the control parameters, an auxiliary control parameter

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[0021] In order to more clearly describe the technical solutions of the present invention, the following briefly introduces the necessary drawings used in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without the need for creative work. [Brief description of the drawings]

[0022] [Figure 1] 2 is a flowchart of an active noise reduction method according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an algorithm block diagram of an active noise reduction method according to an embodiment of the present invention. [Diagram 3] 1 is a block diagram of an active noise reduction device according to an embodiment of the present invention; [Figure 4] FIG. 11 is a comparative diagram showing the change in noise energy depending on the number of iterations. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] In order to facilitate understanding of the advantages and features of the present invention by those skilled in the art, preferred embodiments of the present invention will be described in detail below with reference to the drawings. Note that the description of these embodiments contributes to understanding the present invention, but does not constitute a limitation on the present invention.

[0024] Unlike passive noise control, the traditional LMS algorithm uses the car audio system to build an inverse signal of the noise signal, forming a secondary sound wave to offset the noise in the target area, reducing noise pollution and improving subjective listening comfort, while adding almost no additional weight to the car, contributing to reducing exhaust gas, and is an environmentally friendly and energy-saving solution. However, the convergence speed of the traditional LMS algorithm is slow, and more than 4000 iterations per month are required to achieve the target amount of noise reduction. Therefore, the momentum-based FxLMS algorithm is further provided, which adds a momentum item by increasing the weight coefficient to the traditional LMS algorithm, and the formula for this momentum item is given. w(n+1)=w(n)-2u w f(n)x(n)+α[w(n)-w(n-1)]

[0025] The last term in this formula is the momentum term. However, the convergence speed of such momentum-based FxLMS algorithm is still slow. In this embodiment, an improved car active noise reduction method based on momentum terms is provided, which further improves the convergence speed of the algorithm, and has faster convergence than the conventional FxLMS algorithm and faster convergence than the momentum-based FxLMS algorithm. Figure 1 shows a flow chart of the method, and Figure 2 shows a block diagram of the improved momentum-based FxLMS algorithm. The active noise reduction method will be described in detail below with reference to Figures 1 and 2.

[0026] (1) Reference signal generation: At each sampling time, the angular frequency ω of the target noise to be reduced is 0 The target noise to be reduced is the noise in the compartment due to the vehicle engine. In this embodiment, the reference signal is generated by the function method. x 1 (n)=sin(ω 0 n) x 2 (n)=cos(ω 0 n) Generate.

[0027] (2) Generation of control signal: Parameter w at the current time i Based on (n) and the reference signal obtained in the previous step, generate a control signal y(n) and feed it back to a sound reproduction unit, such as a speaker of a car audio system, which is a car speaker located in the vehicle compartment, for reproducing secondary sound waves into the compartment so as to cancel the noise in the compartment caused by the engine.

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[0028] (4) Generating the reference signal after filtering: The most important step in the FxLMS algorithm is to filter the reference signal. In general, the transfer function of the secondary channel includes the digital control signal y(n) passing through the transmission path of the DAC module, analog filter, power amplifier module, speaker, sound wave propagation in space, microphone, analog filter, and ADC module. The transfer function S of the secondary channel is obtained by online or offline system identification method and expressed as S′, which is a digital filter of length N, where S′=[s 0 ,s 2 ,…s N-1 The calculated sampled reference signal is:

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[0029] (5) Estimate the noise signal. Based on the error signal e(n) collected by the microphone, together with an estimate of the secondary channel transfer function, the actual noise field signal

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[0030] (6) Auxiliary control parameters

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[0031] (7) New auxiliary control parameters

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[0032] (8) Control parameter w i (n). This formula is similar to the formula for updating the control parameters of the conventional FxLMS algorithm. The difference is that the auxiliary control parameters

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[0033] As shown in Fig. 3, the active noise reduction device for a vehicle of this embodiment includes a memory 102, a processor 101, and a computer program stored in the memory and executable by the processor 101, and when the processor 101 executes the program, the above-mentioned active noise reduction method is realized. The memory 102 and the processor 101 are components of a car audio system, that is, the active noise reduction device performs active noise control using the car audio system. The active noise reduction device further includes a sound reproduction device 103 for performing electroacoustic conversion based on the control signal y(n), and specifically, the car speakers of the car audio system include, but are not limited to, headrest speakers, ceiling speakers, door panel speakers, etc. The active noise reduction device further includes a microphone 104 arranged in the area of ​​the compartment to be subjected to noise reduction, for collecting error signals. Simulation Example

[0034] The convergence performance of the algorithm is simulated. In the simulation test, the target noise is a single-frequency signal with a frequency of 167Hz, which is a frequency within the general control band of active noise control, especially car active noise control. Considering a practical noise environment, the environmental noise is set to white noise. The signal-to-noise ratio of the entire noise signal is 10dB. The active noise control is simulated using the conventional FxLMS (Filtered-x Least Mean Square) algorithm, the momentum-based FxLMS algorithm, and the improved MFxLMS algorithm of this embodiment. Figure 4 shows the relationship of the change in the energy of the remaining noise according to the number of iterations of the adaptive control algorithm. As can be seen from FIG. 4, the conventional FxLMS algorithm can effectively reduce noise, but the convergence of the algorithm is relatively slow, requiring 4000 iterations to achieve 7 dB noise reduction; whereas the momentum-based FxLMS algorithm can achieve noise reduction equivalent to that of the conventional FxLMS algorithm, but the convergence speed is faster, requiring only 2500 iterations to achieve convergence; whereas the improved momentum-based MFxLMS algorithm presented in this embodiment has an even faster convergence speed, requiring only 1800 iterations to achieve convergence.

[0035] Those skilled in the art will understand that the singular forms "a," "one," "said," and "this," as used herein, may also include the plural, unless otherwise indicated. Furthermore, it should be understood that the term "comprising," as used in the specification of this application, refers to the presence of features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0036] The above examples are merely for illustrating the technical ideas and features of the present invention, and are preferred embodiments, with the aim that those skilled in the art can understand the contents of the present invention and practice it, but they do not limit the scope of protection of the present invention. Any equivalent changes or modifications made substantially according to the idea of ​​the present invention shall be included in the scope of protection of the present invention.

Claims

1. Angular frequency ω of the target noise to be reduced ０ Based on the two reference signals x １ (n) and x ２ (n), where n represents a time; Step S2 of generating a control signal y(n) according to the following formula (1) and feeding it back to the sound reproducing device, [0010] W ｉ Step S2, where (n) represents the control filter coefficient at the current time; The reference signal obtained in step S1 is filtered to obtain a filtered reference signal shown in the following formula (2): [0025] Step S3 of obtaining [0030] k=0, 1, . . . N-1, where N is the length of the filter and s ｋ represents the coefficients of the transfer function model filter of the secondary channel, the transfer function of the secondary channel being a mathematical model of the transfer path from the sound reproducer to the sound signal collector, and x ｉ Step S3, where (n−k) represents the k-th sampling time value after the i-th reference signal; The noise signal is calculated by the following equation (3): [0045] A step S4 of estimating [0050] and step S4, in which e(n) represents an error signal in signal processing and y(n-k) represents numerical values ​​at the first k sampling times of a control signal fed back to the sound reproduction device, The active noise reduction method includes: The auxiliary control parameter is calculated by the following formula (4). [006] Step S5 of updating [0070] λ represents the constraint factor, and w ｉ Step S5, in which (n-1) represents the control filter coefficient at the last sampling time; The error signal based on the new auxiliary control parameters is expressed by the following equation (5): [0080] Step S6 of calculating [0097] Step S7 of updating the control parameters according to the following formula (6): [0010] μ represents the convergence factor, and w ｉ Step S7, where (n+1) represents the control filter coefficient for the first sampling time in the future. A method for active noise reduction in a vehicle.

2. In step S1, two reference signals x １ (n) and x ２ (n) is represented by the following formula, + １ (n) = sin (ω) ０ n) + ２ (n) = cos (ω) ０ n) 2. The active noise reduction method according to claim 1,

3. In step S2, the sound reproduction device is a car speaker.

2. The active noise reduction method according to claim 1,

4. The car speaker includes at least one of a headrest speaker, a ceiling speaker, and a door panel speaker.

4. The active noise reduction method according to claim 3.

5. In step S4, the error signal e(n) is collected and acquired by a microphone.

2. The active noise reduction method according to claim 1,

6. The target noise to be reduced is the noise from the vehicle engine.

2. The active noise reduction method according to claim 1,

7. 1. An active noise reduction device for a vehicle, comprising: a memory; a processor; and a computer program stored in the memory and executable by the processor, When the processor executes the program, the processor realizes the active noise reduction method according to any one of claims 1 to 6. An active noise reduction device for a vehicle.

8. The active noise reduction device further includes a sound reproducer for performing electroacoustic conversion based on the control signal y(n).

8. An active noise reduction device according to claim 7.

9. The sound reproduction device includes a car speaker disposed within a vehicle compartment.

9. An active noise reduction device according to claim 8.

10. The car speaker includes at least one of a headrest speaker, a ceiling speaker, and a door panel speaker.

10. An active noise reduction device according to claim 9.

11. The active noise reduction device further includes a microphone disposed within a vehicle compartment for collecting the error signal.

8. An active noise reduction device according to claim 7.

12. A computer program is stored which, when executed by a processor, implements the active noise reduction method according to any one of claims 1 to 6. A computer-readable storage medium comprising:

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