A semi-coupled active noise reduction method and system

Abstract

The present invention discloses a semi-coupled active noise reduction method and system; the method comprises: establishing a typical model of far-field noise reduction based on the Rayleigh-Sommerfeld diffraction formula; designing a filter executed in an active noise reduction controller in combination with the typical model of far-field noise reduction; receiving noise source sound waves in real time by means of multiple active noise reduction controllers installed on a sound barrier, and calculating and obtaining sound wave signals of the noise source orientation; filtering the sound wave signals by means of a filter, and calculating an equivalent secondary sound source driving signal; the active noise reduction controller emits a cancelling sound wave according to the secondary sound source driving signal, and forms a sound cancellation with the noise source sound wave behind the sound barrier, thereby achieving active noise reduction. The method takes into account the advantages of both decentralized and centralized noise reduction methods, and improves the effect of active noise reduction.

Description

Technical Field

[0001] The present invention belongs to the technical field of noise control, and in particular relates to a semi-coupled active noise reduction method and system. Background Art

[0002] Noise pollution exists in a variety of settings, including outdoor environments, workplaces, and homes. It is a significant source of pollution that has a significant impact on the human body. Numerous studies have shown that prolonged exposure to noise not only reduces work efficiency but can also harm hearing and physical and mental health. Using sound-insulating panels to isolate the path of sound propagation is a common protective measure. Generally, it's impossible to completely enclose and isolate the sound source, so sound insulation measures typically take the form of barriers. Since sound waves have the ability to diffract, sound barriers cannot completely eliminate noise within the sound shadow zone. Consequently, many approaches have been devised to improve the noise reduction capabilities of sound barriers, and adding active noise reduction technology to sound barriers is one such approach.

[0003] By artificially creating a controlled sound source (secondary sound source) on the sound barrier, the sound it emits has the same amplitude but opposite phase to the noise radiated by the original traffic noise source (primary sound source). This creates a sound cancellation behind the sound barrier, thereby "actively" reducing the impact of traffic noise. While active noise reduction is theoretically feasible, it presents numerous challenges in practice.

[0004] Based on current research, active noise reduction technology is primarily applied to sound barriers in two forms: centralized and decentralized system designs. Centralized designs employ a multi-channel centralized system, with a unified processing unit processing all channels and combining near-field and / or far-field error sensor signals to implement noise reduction within a designated area. This approach typically achieves a certain optimization strategy, but suffers from system complexity and is limited by the number of channels. As the number of channels increases, system complexity increases dramatically, making large-scale deployment impractical. Decentralized designs, on the other hand, decompose the centralized computation of a single controller into multiple controllers, each running independently. Typically, a series of single-channel controllers are used to control the sound field at localized near-field points, creating a soft boundary effect at the top of the sound barrier to suppress diffracted sound. Because decentralized designs employ only localized noise reduction strategies, their noise reduction effectiveness in the target area is often lower than that of centralized systems, failing to achieve the desired noise reduction effect.

[0005] Both the centralized design and the decentralized design of multi-channel active noise reduction have their advantages and disadvantages. Therefore, how to combine the advantages of the two, avoid their disadvantages, and further improve the active noise reduction effect of the sound barrier has become a key issue in current research. Summary of the Invention

[0006] In view of the above problems, the present invention provides a semi-coupled active noise reduction method and system that solves at least some of the above technical problems. This method takes into account the advantages of both decentralized and centralized noise reduction methods, and improves the effect of active noise reduction. The system has a simple structure and is easy to install. It is composed of a series of independent active noise reduction controllers. When a problem occurs in a single active noise reduction controller, it will not affect the overall operation and is also easy to replace. At the same time, using this method can make the noise reduction system operate in the optimal state, and also improve the noise reduction performance.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In a first aspect, an embodiment of the present invention provides a semi-coupled active noise reduction method, comprising the following steps:

[0009] S1. Establish a typical model of far-field noise reduction based on the Rayleigh-Sommerfeld diffraction formula;

[0010] S2. Designing a filter implemented in an active noise reduction controller based on the typical model of far-field noise reduction;

[0011] S3, using multiple active noise reduction controllers installed on the sound barrier to receive noise source sound waves in real time and calculate and obtain sound wave signals indicating the direction of the noise source;

[0012] S4, filtering the sound wave signal using the filter to calculate an equivalent secondary sound source driving signal;

[0013] S5. The active noise reduction controller emits a cancelling sound wave according to the secondary sound source driving signal, which cancels out the sound wave of the noise source behind the sound barrier to achieve active noise reduction.

[0014] Furthermore, in step S1, the typical far-field noise reduction model is:

[0015]

[0016] Among them, z P is the vertical distance from the receiving point behind the barrier to the barrier, k is the wave number, defined as 2π / λ, λ is the wavelength, and j is the imaginary unit.

[0017] Furthermore, in step S2, before designing the filter, a test system is established to perform testing to obtain the response function of the active noise reduction controller. The specific steps are:

[0018] Set a signal source to generate a voltage signal;

[0019] The signal source is connected between the reference microphone and the DSP processor in the active noise reduction controller to provide the signal to the DSP processor;

[0020] The DSP processor works in a direct-through mode, providing a signal to the control sound source, which radiates sound energy and is received by the error microphone;

[0021] Through testing, the response function of the active noise reduction controller is obtained as Hs=H / Hq, where H is the signal transfer function between the test source and the error microphone; and Hq is the sound transfer function between the control sound source and the error microphone.

[0022] Furthermore, in step S2, the filter is:

[0023] Hf=Φ(z P )*Hq / H

[0024] Where H is the signal transfer function between the test source and the error microphone; Hq is the acoustic transfer function between the control sound source and the error microphone.

[0025] Furthermore, in step S3, the active noise reduction controller is installed at the top of the sound barrier at a preset interval.

[0026] Furthermore, the active noise reduction controller is provided with a receiving microphone array, which receives the noise source sound waves in real time, uses a time delay estimation algorithm to determine the noise source orientation, and uses a beamforming algorithm to calculate and obtain the sound wave signal of the noise source orientation.

[0027] Furthermore, the delay estimation algorithm is:

[0028]

[0029] Δl=Δs*v

[0030] Among them, θ is the azimuth of the sound source, Δl is the distance of signal delay, Δd is the distance between channels, v is the speed of sound wave propagation in air, and Δs is the time delay.

[0031] In a second aspect, an embodiment of the present invention further provides an active noise reduction system, which applies the above-mentioned semi-coupled active noise reduction method to achieve active noise reduction. The system includes:

[0032] Sound barriers and multiple active noise reduction controllers, among which,

[0033] Multiple active noise reduction controllers are installed on the top of the sound barrier at a preset interval. The multiple active noise reduction controllers are used to receive noise source sound waves in real time, and emit canceling sound waves based on the noise source sound waves, forming sound cancellation with the noise source sound waves behind the sound barrier to achieve active noise reduction.

[0034] Furthermore, the active noise reduction controller includes: a housing, an upper cover, a reference microphone, a DSP processor, a speaker, an error microphone, and a receiving microphone array; wherein:

[0035] The reference microphone, the loudspeaker, the error microphone and the receiving microphone are respectively connected to the DSP processor;

[0036] The reference microphone, DSP processor, speaker, error microphone and receiving microphone array are installed inside the shell; the receiving microphone array is set at the position of the reference microphone and is used to identify the direction of the noise source sound wave.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. The present invention takes into account the advantages of both decentralized and centralized noise reduction methods, and improves the active noise reduction effect of the sound barrier. The method of the present invention can make the noise reduction system operate in the best state and also improve the noise reduction performance.

[0039] 2. The system structure of the present invention is simple and easy to install. It is composed of a series of independent controllers. When a single controller has a problem, it will not affect the overall operation and is also easy to replace.

[0040] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings.

[0041] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0043] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0044] Figure 1 A flowchart of a semi-coupled active noise reduction method provided by an embodiment of the present invention;

[0045] Figure 2A schematic diagram of the diffraction of a sound barrier provided in an embodiment of the present invention;

[0046] Figure 3 A schematic diagram of a test system provided by an embodiment of the present invention;

[0047] Figure 4 A schematic diagram of sound source identification and positioning provided by an embodiment of the present invention;

[0048] Figure 5 A schematic diagram of simulation results using a common distributed noise reduction method provided by an embodiment of the present invention;

[0049] Figure 6 A schematic diagram of simulation results using the noise reduction method of the present invention provided in an embodiment of the present invention;

[0050] Figure 7 A schematic structural diagram of an active noise reduction system provided by an embodiment of the present invention;

[0051] Figure 8 This is a structural diagram of the active noise reduction controller provided by an embodiment of the present invention;

[0052] Figure 9 A diagram showing the internal structure of the housing of the active noise reduction controller provided by an embodiment of the present invention;

[0053] Figure 10 This is an exploded view of the active noise reduction controller provided by an embodiment of the present invention.

[0054] in, Figure 7 and Figure 10 Middle: 1-active noise reduction controller, 2-sound barrier, 11-reference microphone, 12-DSP processor, 13-speaker, 14-error microphone. DETAILED DESCRIPTION

[0055] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0056] In some processes described in the specification and claims of this application and the above-mentioned drawings, multiple operations appearing in a specific order are included, but it should be clearly understood that these operations may not be performed in the order in which they appear in this document or may be performed in parallel.

[0057] In the description of the invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," "the other end," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0058] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0059] Example 1:

[0060] like Figure 1 As shown, an embodiment of the present invention provides a semi-coupled active noise reduction method, which specifically includes:

[0061] S1. Establish a typical model of far-field noise reduction based on the Rayleigh-Sommerfeld diffraction formula;

[0062] S2. Designing a filter implemented in an active noise reduction controller based on the typical model of far-field noise reduction;

[0063] S3, using multiple active noise reduction controllers installed on the sound barrier to receive noise source sound waves in real time and calculate and obtain sound wave signals indicating the direction of the noise source;

[0064] S4, filtering the sound wave signal using the filter to calculate an equivalent secondary sound source driving signal;

[0065] S5. The active noise reduction controller emits a cancelling sound wave according to the secondary sound source driving signal, which cancels out the sound wave of the noise source behind the sound barrier to achieve active noise reduction.

[0066] The following is a detailed description of the above steps:

[0067] In the above step S1, see Figure 2 As shown, the embodiment of the present invention starts from the sound barrier diffraction theory, based on the rigorous analytical solution of the Rayleigh-Sommerfeld diffraction formula for the sound wave scattering of the half-space sound barrier, and derives it under the condition of far-field propagation to obtain the barrier surface line integral form of sound wave scattering, which is used as a guide for the design of active sound barrier parameters.

[0068] For plane wave incidence, the incident angle is θ, and the sound wave intensity evaluation quantity incident on the sound barrier plane at each position above the sound barrier is set to U(Q). Then the sound wave intensity U(P) at any point behind the sound barrier is calculated according to the Rayleigh-Sommerfeld diffraction formula:

[0069]

[0070] Where λ is the wavelength of the sound wave, k is the wave number, and r is the distance from each point above the sound barrier plane to the receiving point. represents the normal direction of the plane above the sound barrier, Indicates the vector direction from each point above the sound barrier plane to the receiving point, is the cosine of the angle between the vector from each point above the sound barrier plane to the receiving point and the plane normal, Σ is the plane above the sound barrier, j represents the imaginary unit, e jkr It represents the phase delay caused by sound propagation, and dS represents the plane microelement area above the sound barrier.

[0071] Furthermore, rewriting the above formula into a line integral form, if the controllers are arranged linearly on top of the sound barrier, it can be theoretically equivalent to achieving the effect of surface integral; then it can be expressed as:

[0072]

[0073] Where V(l) is the linear offset sound wave intensity emitted by the controller at the top of the sound barrier, z P is the vertical distance from the receiving point behind the barrier to the barrier, l represents the position coordinate at the top line of the sound barrier, and B represents the top boundary of the sound barrier.

[0074] Under the condition of far-field propagation, it can be derived that:

[0075] V(l)=Φ(l,z P )U(l,h)

[0076] Where U(l,h) is the sound wave intensity evaluation value incident on each controller position on the top of the sound barrier, which is also the sound signal received by the controller reference microphone. h represents the height of the sound barrier. Φ(l,z P ) is the function that the controller needs to implement. This parameter is related to l and z P related.

[0077] Φ(l,z P ) can be further simplified to accommodate rapid controller design calculations and can be simplified to:

[0078]

[0079] Where D(z P) is a constant related to the distance from the receiving point, Represents the change in the phase of the sound wave.

[0080] The typical model for far-field noise reduction is further established as follows:

[0081]

[0082] Among them, Φ(z P ) and distance z P The choice of is also related to the frequency, so when using this formula for calculation, it is necessary to pre-set the approximate optimal design distance. The secondary sound of the controller is assigned the value according to the formula derived by the present invention, which can achieve an optimized effect. P ) is expressed as a frequency response function. According to this frequency response function, the corresponding filtering curve is designed, which can theoretically achieve an optimized noise reduction in the far field area.

[0083] If we further consider not arranging the controllers at unit distances, but assuming that they are evenly distributed at intervals d, the frequency response function needs to be further modified as follows:

[0084]

[0085] In step S2 above, before designing the filter, the embodiment of the present invention further establishes a test system for testing to obtain the active noise reduction controller's own response function; and then, in combination with the above-mentioned typical model of far-field noise reduction, designs the filter executed in the active noise reduction controller, specifically:

[0086] Build a test system. The test can be conducted in an anechoic chamber or outdoors in an open area protected from external noise. The test also requires an additional signal source to generate voltage or acoustic signals and a multi-channel test system to determine the signal transfer function of the two channels.

[0087] When the reference microphone and the error microphone are of the same model and have the same sensitivity, a simplified measurement method is given as an example. Figure 3 As shown, the signal source is connected between the reference microphone and the DSP signal and provides the DSP processor with signal s. During the measurement phase, the DSP processor first operates in a direct-through mode, providing signal q to the control sound source (including the power amplifier). The control sound source radiates acoustic energy, which is received by the error microphone at the error microphone position and converted into an electrical signal p. The radiation from the control sound source can be considered as point source radiation during testing, so the signal transmission path between the radiation and the error microphone can be calculated using the acoustic radiation formula to obtain Hq. Simultaneously, the signal transfer function between the signal source and the error microphone can also be obtained: H = p / s. Through testing, the controller system's self-response function, Hs = H / Hq, was obtained.

[0088] According to the frequency response function Φ(z P ), so the filter design is required in the controller DSP, and the filter is designed according to the transfer function Hf=Φ(z P )*Hq / H for design.

[0089] In the above step S3, multiple active noise reduction controllers are installed on the sound barrier to receive the sound waves of the noise source in real time. In specific implementation, the active noise reduction controllers are installed at the top of the sound barrier at a preset interval. The active noise reduction controllers are provided with a receiving microphone array. The receiving microphone array receives the sound waves of the noise source in real time, and then the controller calculates and obtains the sound wave signal of the noise source direction; specifically:

[0090] When noise reduction is turned on, the incident source monitoring sensor array (i.e., receiving microphone array) is used to analyze the direction of the noise source in real time and extract the sound source intensity and direction information. The main purpose of using the sensor array is to filter out the influence of the speaker of the other controller (the speaker of the own controller or the speaker of other controllers) on the controller to solve the problem of secondary sound feedback. This process can be implemented using a time delay estimation method to estimate the arrival time delay of the sound source signal between each sensor, use the time delay to determine the direction of the sound source, and use the beamforming algorithm to extract the sound wave signal of the direction of the sound source. The time delay estimation method used in this process is only an example of this embodiment, and other algorithms can also be used. The problem of sound source direction estimation usually uses a group of microphones placed in a certain geometric position to determine the spatial position of the sound source. According to the positioning principle, it can be roughly divided into three categories: (1) controllable beamforming technology based on maximum output power; (2) technology based on arrival time difference TDOA; (3) positioning technology based on high-resolution spectrum estimation. The time delay estimation positioning algorithm used in this embodiment is only an implementation method of the embodiment of the present invention and does not limit it.

[0091] The present invention requires azimuth estimation of the target signal and extraction of the time-domain signals of each channel through denoising. Therefore, the most effective approach is to identify the direction of arrival using high-resolution spectral estimation and extract the ambient sound source signals in that direction using spatial filtering. However, to facilitate real-time operation on embedded platforms, it is more practical to use the less computationally intensive correlation delay estimation method to achieve azimuth estimation of the external sound source signal and filter signal extraction.

[0092] For the convenience of analysis, we take the far-field model as an example. The far-field model is a plane wave before reaching the microphone array element, such as Figure 4 As shown, the direction angles of the sound source arriving at the microphone array are the same;

[0093] It is known that the propagation speed of sound waves in air is v. If the time delay between any two channels is Δs, then the distance of signal delay Δl = Δs*v. Taking adjacent channels as an example, the azimuth angle θ of the sound source can be calculated in this way:

[0094]

[0095] The delay of each channel signal can be estimated, and the corresponding delay compensation is made and the average value of each channel is calculated to obtain the instantaneous average value of the sound wave intensity evaluation. and the azimuth average

[0096] The sound wave intensity evaluation value U(l,h) at the controller position is calculated using the formula:

[0097]

[0098] Furthermore, by filtering the above-designed filter on the above-mentioned sound wave signal, the equivalent secondary sound source (control sound source) driving signal can be calculated;

[0099] Furthermore, the active noise reduction controller emits a cancelling sound wave according to the secondary sound source driving signal, which cancels out the noise source sound wave behind the sound barrier (at the position of the equivalent sound source evaluation surface), thereby achieving active noise reduction.

[0100] In the embodiment of the present invention, since only the reference microphone and the control sound source are involved in the noise reduction phase, the main tasks are divided into two parts: first, real-time detection and calculation of the sound source position and extraction of sound source information; second, the transfer function Hf between the incident sound monitoring sensor and the receiving point is calculated to generate the real-time driving vector of the equivalent sound source (secondary sound source array) to drive the secondary sound source array to operate and implement noise reduction. Since the transfer function Hf between the incident sound monitoring sensor and the equivalent sound source has been obtained, the noise reduction work only requires filtering the signal with a filter designed according to this function, that is, calculating the output signal of the equivalent sound source. The above processing achieves decoupling between the unit and the system. That is, a single controller only needs to perform processing according to a predetermined program, independent of other controllers, and can therefore be easily deployed and replaced. The operation of each processor automatically forms an optimized noise reduction effect at the system level. That is, the method of the present invention retains the systematic nature of the design and the decentralized nature of the execution level, forming a semi-coupled design, which improves the active noise reduction effect and noise reduction performance.

[0101] Furthermore, in the embodiment of the present invention, numerical simulation experiments were carried out on the common distributed noise reduction method and the method of the present invention, and the simulation results are as follows: Figure 5 and Figure 6 As shown; after the simulation analysis, Figure 5 and Figure 6By comparison, it can be seen that the method of the present invention achieves an additional noise reduction effect of more than 3dB.

[0102] Example 2:

[0103] like Figure 7 As shown, an embodiment of the present invention further provides an active noise reduction system, which is applied to a semi-coupled active noise reduction method of the above embodiment to achieve active noise reduction; the system is mainly composed of multiple active noise reduction controllers 1 and sound barriers 2, wherein,

[0104] In this embodiment, referring to Figures 8-10 As shown, the active noise reduction controller 1 mainly includes: a reference microphone 11, a DSP processor 12 (i.e., a digital signal control unit), a speaker 13, and an error microphone 14. A receiving microphone array is designed at the position of the reference microphone to identify the azimuth of the incoming wave. Figure 7 As shown, the active noise reduction controller 1 is installed at a certain interval on the top of the sound barrier 2. The active noise reduction controller 1 is used to receive the sound waves of the noise source in real time, and emit a canceling sound wave according to the sound waves of the noise source, forming a sound cancellation with the sound waves of the noise source behind the sound barrier 2 to achieve active noise reduction; its specific working principle can be found in the implementation part of the above method, which will not be repeated here.

[0105] From the above description of the embodiments, it can be seen that the present invention provides an active noise reduction system with a simple hardware structure, easy use and installation, strong adaptability and application promotion value.

[0106] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0107] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A semi-coupled active noise reduction method, characterized in that: The following steps are involved: S1. Establish a typical model of far-field noise reduction based on the Rayleigh-Sommerfeld diffraction formula; For plane wave incidence, the incident angle is θ, and the sound wave intensity evaluation quantity incident on the sound barrier plane at each position above the sound barrier is set to U(Q). Then the sound wave intensity U(P) at any point behind the sound barrier is calculated according to the Rayleigh-Sommerfeld diffraction formula: Where λ is the wavelength of the sound wave, k is the wave number, and r is the distance from each point above the sound barrier plane to the receiving point. represents the normal direction of the plane above the sound barrier, Indicates the vector direction from each point above the sound barrier plane to the receiving point, is the cosine of the angle between the vector from each point above the sound barrier plane to the receiving point and the plane normal, Σ is the plane above the sound barrier, j represents the imaginary unit, e jkr represents the phase delay caused by sound propagation, and dS represents the plane microelement area above the sound barrier; Rewrite the above formula into line integral form, expressed as: Where V(l) is the linear offset sound wave intensity emitted by the controller at the top of the sound barrier, z P is the vertical distance from the receiving point behind the barrier to the barrier, l represents the coordinate of the position on the top line of the sound barrier, and B represents the top boundary of the sound barrier; Under the condition of far-field propagation, it is derived that: V(l)=Φ(l,z P )U(l,h) Among them, U(l,h) is the sound wave intensity evaluation value incident on each controller position on the top of the sound barrier, which is also the sound signal received by the controller reference microphone. h represents the height of the sound barrier; Φ(l,z P ) is the function that the controller needs to implement. This parameter is related to l and z P related; Φ(l,z P ) is simplified to accommodate the rapid design calculation of the controller and is simplified to: Among them, D(z P ) is a constant related to the distance from the receiving point, Indicates the change in the phase of the sound wave; The typical model for far-field noise reduction is: Among them, Φ(z P ) is the frequency response function, z P is the vertical distance from the receiving point behind the barrier to the barrier, k is the wave number, defined as 2π / λ, λ is the wavelength, and j is the imaginary unit; S2. Designing a filter implemented in an active noise reduction controller based on the typical model of far-field noise reduction; S3, using multiple active noise reduction controllers installed on the sound barrier to receive noise source sound waves in real time and calculate and obtain sound wave signals indicating the direction of the noise source; S4, filtering the sound wave signal using the filter to calculate an equivalent secondary sound source driving signal; S5. The active noise reduction controller emits a cancelling sound wave according to the secondary sound source driving signal, which cancels out the sound wave of the noise source behind the sound barrier to achieve active noise reduction.

2. A semi-coupled active noise reduction method according to claim 1, characterized in that: In step S2, before designing the filter, a test system is established to perform testing and obtain the response function of the active noise reduction controller. The specific steps are as follows: Set a signal source to generate a voltage signal; The signal source is connected between the reference microphone and the DSP processor in the active noise reduction controller to provide the signal to the DSP processor; The DSP processor works in a direct-through mode, providing a signal to the control sound source, which radiates sound energy and is received by the error microphone; Through testing, the response function of the active noise reduction controller is obtained as Hs=H / Hq, where H is the signal transfer function between the test source and the error microphone, and Hq is the sound transfer function at the position of the control sound source and the error microphone.

3. The semi-coupled active noise reduction method according to claim 1, characterized in that: In step S2, the filter is: Hf=φ(z P )*Hq / H Where H is the signal transfer function between the test source and the error microphone; Hq is the acoustic transfer function between the control sound source and the error microphone.

4. The semi-coupled active noise reduction method according to claim 1, characterized in that: In step S3, the active noise reduction controller is installed at the top of the sound barrier at a preset interval.

5. The semi-coupled active noise reduction method according to claim 4, characterized in that: The active noise reduction controller is provided with a receiving microphone array, which receives the noise source sound waves in real time, adopts a time delay estimation algorithm to determine the noise source direction, and uses a beamforming algorithm to calculate and obtain the sound wave signal of the noise source direction.

6. The semi-coupled active noise reduction method according to claim 5, characterized in that: The delay estimation algorithm is: Δl=Δs*v Among them, θ is the azimuth of the sound source, Δl is the distance of signal delay, Δd is the distance between channels, v is the speed of sound wave propagation in air, and Δs is the time delay.

7. An active noise reduction system, characterized in that: A semi-coupled active noise reduction method according to any one of claims 1 to 6 is applied to achieve active noise reduction.

8. The active noise reduction system according to claim 7, characterized in that: The system includes: multiple active noise reduction controllers and sound barriers, wherein, Multiple active noise reduction controllers are installed on the top of the sound barrier at a preset interval. The multiple active noise reduction controllers are used to receive noise source sound waves in real time, and emit canceling sound waves based on the noise source sound waves, forming sound cancellation with the noise source sound waves behind the sound barrier to achieve active noise reduction.

9. The active noise reduction system according to claim 8, characterized in that: The active noise reduction controller includes: a housing, an upper cover, a reference microphone, a DSP processor, a speaker, an error microphone, and a receiving microphone array; wherein: The reference microphone, the loudspeaker, the error microphone and the receiving microphone are respectively connected to the DSP processor; The reference microphone, DSP processor, speaker, error microphone and receiving microphone array are installed inside the shell; and the receiving microphone array is set at the position of the reference microphone for identifying the direction of the noise source sound wave.

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