An active noise reduction method, device, and storage medium for a vehicle

Abstract

The present invention discloses an active noise reduction method and device for a vehicle. The active noise reduction method includes: generating a reference signal according to a target noise to be reduced, and generating a control signal fed to a sound reproduction device; filtering the reference signal, calculating a noise signal based on an error signal, and updating an auxiliary control parameter; updating the error signal according to the filtered reference signal, the noise signal, and the auxiliary control parameter; and updating the control parameter according to the updated error signal and the auxiliary control parameter. The present invention can reduce the in-vehicle noise pollution and has a relatively fast convergence speed.

Description

Technical Field

[0001] The present invention belongs to the field of vehicle noise control, and relates to an active noise reduction method and device for a vehicle, and a storage medium. Background Art

[0002] With the development of modern industry, the problem of noise pollution has attracted more and more attention, and high-intensity noise signals also affect the comfort of listeners. Due to the effect of acoustic masking, it is necessary to increase the volume to obtain a higher signal-to-noise ratio for a clear listening effect. The long-term continuous high sound pressure brought about in this way will cause irreversible damage to hearing. With the improvement of vehicle intelligence, the requirements of passengers and drivers for the in-vehicle acoustic environment are becoming increasingly strict. In-vehicle noise will reduce the comfort of passengers and drivers, cause irritability and fatigue of vehicle occupants; it will also affect the clarity of communication calls, and even affect the driver's perception of external signal sounds of the vehicle, increasing traffic hazards. Automotive NVH (Noise, Vibration, Harshness) is an important issue that vehicle manufacturers are concerned about. Modifying the structural design, adding damping materials or using shock-absorbing springs and other devices to reduce noise are collectively referred to as passive noise control; this method has a relatively good noise reduction effect on medium and high-frequency noises. However, this method has a relatively poor effect on low frequencies, especially the noise of the engine in the vehicle compartment, which often concentrates on low frequencies. In addition, passive noise control requires a long tuning time and is difficult to control costs. The active noise reduction solution uses the in-vehicle audio system to construct an anti-signal of the noise signal, form a secondary sound wave, cancel the noise in the target area, reduce noise pollution, improve the subjective listening comfort, but hardly adds extra weight to the vehicle, which helps to reduce exhaust emissions and is a green and energy-saving solution.

[0003] The LMS algorithm is a traditional in-vehicle active noise reduction solution, but its convergence speed is slow. Subsequently, a FxLMS (Filtered-x, Least Mean Square) algorithm based on momentum was proposed, which adds a momentum term due to the increase of the weight coefficient in the traditional LMS algorithm. Although the FxLMS algorithm based on momentum improves the convergence speed of the traditional LMS algorithm, the convergence speed of this method is still slow. Summary of the Invention

[0004] The purpose of the present invention is to provide an active noise reduction method for a vehicle, which can actively reduce the noise of the vehicle engine, reduce in-vehicle noise pollution and has a fast convergence speed.

[0005] Another purpose of the present invention is to provide an active noise reduction device for a vehicle that adopts the above active noise reduction method.

[0006] The 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.

[0007] According to the first aspect of the present invention, an active noise reduction method for a vehicle includes the following steps:

[0008] A. Generate two reference signals x 0 (n) and x 1 (n), where n represents the time; 2 (n), where n represents the time;

[0009] B. Generate a control signal y(n) according to the following formula (1) and feed it to the sound reproduction device,

[0010]

[0011] where w i (n) represents the control filter coefficient at the current time, and this coefficient is adaptively updated, which is described in detail in step E;

[0012] C. Filter the reference signal obtained in step A to obtain the filtered reference signal as shown in the following formula (2)

[0013]

[0014] where k = 0, 1,... N-1, N represents the length of the filter, s k represents the coefficient of the transfer function model filter of the secondary channel; the transfer function of the secondary channel is the mathematical model of the transfer path from the sound reproduction device (loudspeaker) to the sound signal acquisition device (microphone), x i (n-k) represents the values of the first k sampling times of the i-th reference signal;

[0015] D. Deduce the noise signal according to the following formula (3)

[0016]

[0017] where e(n) represents the error signal in the sense of signal processing, and physically it is the signal collected by the microphone, and y(n-k) represents the values of the first k sampling times of the control signal fed to the loudspeaker;

[0018] The active noise reduction method further includes the following steps:

[0019] E. Update the auxiliary control parameters according to the following formula (4)

[0020]

[0021] Among them, λ represents a constraint factor, which is a relatively small constant, and w i (n - 1) represents the control filter coefficients at the previous sampling time;

[0022] F. Calculate the error signal based on the new auxiliary control parameter according to the following formula (5)

[0023]

[0024] G. Update the control parameter according to the following formula (6),

[0025]

[0026] Among them, μ represents a convergence factor, and w i (n + 1) represents the control filter coefficients at the next sampling time.

[0027] In one embodiment, in step A, two reference signals x 1 (n) and x 2 (n) are generated according to the function method as shown in the following formulas respectively,

[0028] x 1 (n) = sin(ω 0 n)

[0029] x 2 (n) = cos(ω 0 n).

[0030] In one embodiment, in step B, the sound reproduction device is a vehicle-mounted speaker.

[0031] In one embodiment, in step D, the error signal e(n) is collected by a microphone.

[0032] In this article, the target noise to be reduced is the noise caused by the vehicle engine. The above-mentioned vehicle-mounted speakers are placed in the vehicle compartment or at least radiate sound towards the vehicle compartment, including but not limited to: headrest speakers, ceiling speakers, door panel speakers, etc.; the above-mentioned microphones are placed in the vehicle compartment or at least can collect the sound signals in the vehicle compartment.

[0033] According to the second aspect of the present invention, an active noise reduction device for a vehicle includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, the above-mentioned active noise reduction method is implemented.

[0034] In one embodiment, the active noise reduction device further includes a sound reproduction device for electro-acoustic conversion according to the control signal y(n).

[0035] In one embodiment, the sound reproduction device includes an in-vehicle speaker. The in-vehicle speaker is disposed inside the vehicle compartment or at least radiates sound towards the vehicle compartment, including but not limited to: headrest speakers, ceiling speakers, door panel speakers, etc.

[0036] In one embodiment, the active noise reduction device further includes a microphone for collecting the error signal. The microphone is disposed inside the vehicle compartment or at least capable of collecting sound signals inside the vehicle compartment.

[0037] According to the third aspect of the present invention, a computer-readable storage medium has a computer program stored thereon, and when the program is executed by a processor, it implements the active noise reduction method described above.

[0038] The present invention adopts the above solutions and has the following advantages compared with the prior art:

[0039] In the vehicle active noise reduction method for vehicle engine noise of the present invention, during the process of updating the control parameters, auxiliary control parameters are used. As the basis for iteration, and the error signal selected is the error signal obtained based on the auxiliary control parameters. The improvement of the control parameters by momentum is advanced, and the algorithm can converge at a relatively fast speed; at the same time, by using the in-vehicle audio system, an anti-signal of the noise signal is established to form a secondary sound wave to cancel the noise in the target area, reduce noise pollution, and improve the subjective listening comfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0041] Figure 1 It is a flowchart of the active noise reduction method according to an embodiment of the present invention.

[0042] Figure 2 It is a block diagram of the algorithm of the active noise reduction method according to an embodiment of the present invention.

[0043] Figure 3 It is a comparison chart of the change of noise energy with the number of iterations. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted here that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation on the present invention.

[0045] Different from passive noise control, the traditional LMS algorithm can utilize the in-vehicle audio system to construct the anti-signal of the noise signal, form a secondary sound wave, cancel the noise in the target area, reduce noise pollution, improve the subjective listening comfort, but hardly adds extra weight to the vehicle, which helps to reduce exhaust emissions and is a green and energy-saving solution. However, the convergence speed of the traditional LMS algorithm is relatively slow, and it needs to be iterated more than 4000 times to achieve the target noise reduction amount. Based on this, the FxLMS algorithm based on momentum is proposed. A momentum term due to the increase of the weight coefficient is added to the traditional LMS algorithm, and the expression of this momentum term is given:

[0046] w(n + 1) = w(n) - 2u w f(n)x(n) + α[w(n) - w(n - 1)]

[0047] The last term of this expression is the momentum term. However, the convergence speed of this FxLMS algorithm based on momentum is still relatively slow.

[0048] This embodiment provides an improved in-vehicle active noise reduction method based on the momentum term, which further improves the convergence speed of the algorithm, making it converge faster than the traditional FxLMS algorithm and faster than the FxLMS algorithm based on momentum. Figure 1 The flowchart of this method is shown, Figure 2 The block diagram of the improved FxLMS algorithm based on momentum is shown. In combination with Figure 1 and Figure 2 The specific description of this active noise reduction method is as follows.

[0049] (1) Reference signal generation: At each sampling moment, according to the angular frequency ω of the target noise to be reduced 0 generate reference signals, that is, sine signals and cosine signals. The target noise to be reduced is the noise caused by the vehicle engine in the carriage.

[0050] This embodiment uses the function method to generate reference signals

[0051] x 1 (n) = sin(ω 0 n)

[0052] x 2 (n) = cos(ω 0n)

[0053] (2) Control signal generation: Based on the parameter w i (n) at the current moment and the reference signal obtained in the previous step, generate a control signal y(n), and feed it to sound reproduction units such as the speakers of the in-vehicle audio system. The speaker is an in-vehicle speaker placed in the vehicle compartment, which is used to play infrasound waves into the compartment in order to cancel out the noise caused by the engine in the compartment.

[0054]

[0055] (4) Generate the filtered reference signal: An important step in the FxLMS algorithm is to filter the reference signal. Generally, it is considered that the transfer function of the secondary channel includes the transfer path of the digital control signal y(n) through the DAC module, analog filter, power amplifier module, speaker, spatial propagation of sound waves, microphone, analog filter, and ADC module. The transfer function S of the secondary channel is obtained through on-line and off-line system identification methods, denoted as S′, which is a digital filter of length N, expressed as S′ = [s 0 , s 2 , … s N-1 . The calculated filtered reference signal is

[0056]

[0057] (5) Estimate the noise signal. Based on the error signal e(n) collected by the microphone and combined with the estimation of the transfer function of the secondary channel, the actual noise field signal can be deduced The microphone is specifically a microphone placed in the compartment, which collects the sound signal in the compartment at the current moment, and then deduces the current actual noise field signal.

[0058] Here, the structure of the MFxLMS algorithm is applied, and the noise signal needs to be re-estimated, specifically expressed as

[0059]

[0060] (6) Update the auxiliary control parameters It is the coefficient combined with the parameter w i (n) at the previous moment and the momentum term

[0061]

[0062] (7) Calculate based on the new auxiliary control parameters The error signal. It is applied to the estimated noise signal, the filtered reference signal, and the auxiliary control parameters. If the transfer function of the secondary channel is accurately estimated and considered to be the same as that of the real physical channel, it can be considered that the estimated noise signal and the filtered reference signal are no different from the real situation. In this case, the difference between the error signal and the error signal e(n) picked up by the microphone is the control parameter and the difference between w i (n). And the difference between the two is the momentum term. That is, the improved momentum term in our algorithm is different from the traditional momentum-based FxLMS algorithm in one aspect. The momentum term improves the control parameter earlier, so the algorithm converges faster. The specific calculation expression is

[0063]

[0064] (8) updates the control parameter w i (n). This expression is similar to the update expression of the control parameter in the traditional FxLMS algorithm. The difference is that here the auxiliary control parameter is used as the basis for iteration, and the error signal selected is the error signal obtained based on the auxiliary control parameter instead of the error signal e(n) directly collected from the microphone. The specific expression is

[0065]

[0066] According to the active noise reduction device of the vehicle in this embodiment, it includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, it implements the active noise reduction method as described above. The memory and the processor are components of the vehicle audio system, that is, the active noise reduction device uses the vehicle audio system for active noise control. The active noise reduction device further includes an acoustic playback device for electro-acoustic conversion according to the control signal y(n), specifically the vehicle speakers of the vehicle audio system, including but not limited to: headrest speakers, ceiling speakers, door panel speakers, etc. The active noise reduction device further includes a microphone for collecting the error signal, which is placed in the area of the carriage that needs noise reduction.

[0067] Simulation example

[0068] The convergence performance of the algorithm was simulated. In the simulation experiment, the target noise was a single-frequency signal with a frequency of 167 Hz, which was a frequency within the typical control frequency band encountered in active noise control, especially vehicle-mounted active noise control. Considering the actual noise environment, the ambient noise was set as white noise. The signal-to-noise ratio of the entire noise signal was 10 dB. The active noise control simulations were respectively carried out using the traditional FxLMS (Filtered-x Least Mean Square) algorithm, the FxLMS algorithm based on momentum, and the improved MFxLMS algorithm of this embodiment. Figure 3 The relationship between the energy of the residual noise and the number of iterations of the adaptive control algorithm was given. From Figure 3 it can be seen that the traditional FxLMS algorithm can effectively reduce noise, but the algorithm converges relatively slowly, and a noise reduction of 7 dB is achieved after 4000 iterations; the FxLMS algorithm based on momentum can achieve a noise reduction equivalent to that of the traditional FxLMS algorithm, but the convergence speed is faster, and convergence is achieved after 2500 iterations; while the improved MFxLMS algorithm based on momentum proposed in this embodiment has a faster convergence speed and achieves convergence after 1800 iterations.

[0069] Those skilled in the art of this technology can understand that unless specifically stated, the singular forms "a", "an", "the", and "said" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the specification of this application means 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.

[0070] The above embodiments are only for illustrating the technical concept and features of the present invention, and are a preferred embodiment. The purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. An active noise reduction method for a vehicle, comprising the following steps: A. According to the angular frequency ω of the target noise to be denoised 0 generate two reference signals x 1 (n) and x 2 (n), Wherein, n represents the time; B. Generate a control signal y(n) according to the following formula (1) and feed it to the sound reproduction device, where, w i (n) represents the control filter coefficients at the current moment; C. Filter the reference signal obtained in step A to obtain a filtered reference signal as shown in the following formula (2). where k = 0, 1, … N - 1, N represents 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 is a mathematical model of the transfer path from the sound reproduction device to the sound signal acquisition device, and x i (n - k) represents the values of the first k sampling moments of the i-th reference signal; D. Calculate the noise signal according to the following formula (3) Wherein, e(n) represents the error signal in the sense of signal processing, and y(n-k) represents the values of the control signal fed to the speaker at the previous k sampling times; The active noise reduction method is characterized in that it further comprises the following steps: E. Update the auxiliary control parameter according to the following formula (4) where λ represents the constraint factor, w i (n - 1) represents the control filter coefficients at the previous sampling time; F. Calculate the error signal based on the new auxiliary control parameter according to the following formula (5) G. Update the control parameters according to the following formula (6), where μ represents the convergence factor, and w i (n + 1) represents the control filter coefficients at the next sampling instant.

2. The active noise reduction method according to claim 1, Characterized in that, In step A, two reference signals x 1 (n) and x 2 (n) are respectively shown as follows: x 1 (n) = sin(ω 0 n) x 2 (n) = cos(ω 0 n).

3. The active noise reduction method according to claim 1, Characterized in that, In step B, the sound reproduction device is an in-vehicle speaker.

4. The active noise reduction method according to claim 1, Characterized in that, In step D, the error signal e(n) is collected by a microphone.

5. The active noise reduction method according to claim 1, Characterized in that, The target noise to be reduced is the noise caused by the vehicle engine.

6. An active noise reduction device for a vehicle, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, Characterized in that, When the processor executes the program, it implements the active noise reduction method according to any one of claims 1 to 5.

7. The active noise reduction device according to claim 6, Characterized in that, The active noise reduction device further comprises a sound reproduction device for electroacoustic conversion according to the control signal y(n).

8. The active noise reduction device according to claim 7, Characterized in that, The sound reproduction device includes an in-vehicle speaker, and the in-vehicle speaker is arranged in the vehicle compartment.

9. The active noise reduction device according to claim 6, Characterized in that, The active noise reduction device further comprises a microphone for collecting the error signal, and the microphone is arranged in the vehicle compartment.

10. A computer-readable storage medium, Characterized in that, A computer program is stored on the computer-readable storage medium, and when the program is executed by a processor, it implements the active noise reduction method according to any one of claims 1 to 5.

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