Active and passive fusion noise reduction method and system for air-cooled low-frequency noise

Abstract

The application discloses a kind of active and passive fusion noise reduction method and system for air-cooled low-frequency noise, belong to electronic equipment noise control technical field.The method includes: obtaining air-cooled low-frequency noise, air-cooled low-frequency noise is emitted to passive sound absorption component, air-cooled low-frequency noise is preprocessed by micro-perforated coupling disc winding cavity sound absorption structure, and composite noise is obtained, composite noise is emitted to active noise control component, and reference signal and residual noise error signal in target area of composite noise are collected by reference sensor and error sensor;Reference signal and residual noise error signal are emitted to controller, and reference signal is operated by wideband control branch and narrowband control branch, and total control signal is obtained, and total control signal is emitted to secondary sound source, so that secondary sound source generates control sound that is offset with air-cooled low-frequency noise, and the synergistic inhibition to air-cooled low-frequency noise is realized.The method realizes the efficient control to air-cooled composite noise.

Description

Technical Field

[0001] This invention belongs to the field of electronic equipment noise control technology, and in particular relates to an active and passive fusion noise reduction method and system for low-frequency noise from air-cooled equipment. Background Technology

[0002] Existing research indicates that the noise in air-cooled heat dissipation systems primarily originates from axial fans, and in the low-frequency range, it typically exhibits a composite characteristic of continuous broadband background noise and discrete narrowband peak noise. For this type of noise, traditional passive noise reduction methods often require thick sound-absorbing structures, making it difficult to balance ventilation, heat dissipation, dimensional constraints, and engineering reliability. On the other hand, active noise reduction methods suffer from problems such as heavy control burden, high causality requirements, significant acoustic feedback, and limited structural layout.

[0003] On the other hand, passive noise reduction structures such as micro-perforated coupled coiled cavities can achieve high absorption efficiency with subwavelength thickness and have good thermal stability, mechanical stability, and environmental adaptability, making them suitable for placement in the air outlet channel or sound propagation path of air-cooled systems. However, such passive structures still struggle to completely suppress residual broadband noise and discrete narrowband peaks under complex operating conditions.

[0004] Existing technologies have technical problems in addressing low-frequency composite noise in air-cooled heat dissipation systems, making it difficult to simultaneously achieve noise reduction effect, structural compactness, ventilation and heat dissipation performance, and engineering reliability. Therefore, there is an urgent need to propose an active-passive fusion noise reduction design method that combines an ultra-thin passive sound-absorbing structure with active noise control technology suitable for open sound fields, so as to achieve efficient suppression of low-frequency composite noise without significantly affecting heat dissipation performance and structural size. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes an active-passive fusion noise reduction method and system for low-frequency noise in air-cooled systems. By combining low-frequency passive sound absorption technology with wide- and narrow-band fusion active noise control technology, the passive noise reduction part is used for front-end preprocessing and absorption of the target low-frequency noise, while the active noise reduction part is used for synergistic suppression of residual continuous broadband noise and discrete narrow-band peak noise, thereby achieving efficient control of air-cooled composite noise.

[0006] In a first aspect, the present invention provides an active-passive fusion noise reduction method for low-frequency noise from air-cooled systems, the method comprising: Low-frequency air-cooled noise is acquired and emitted into a passive sound-absorbing component. The low-frequency air-cooled noise is pre-processed through a micro-perforated coupled coiled cavity sound-absorbing structure to obtain composite noise. The micro-perforated coupled coiled cavity sound-absorbing structure includes a micro-perforated plate, a coiled cavity, and a base plate. Multiple micro-holes are formed on the micro-perforated plate. The low-frequency air-cooled noise passes through the micro-holes and enters the coiled cavity. The composite noise includes broadband noise and narrowband noise. The composite noise is transmitted to the active noise control component, and the reference signal of the composite noise and the residual noise error signal in the target area are acquired by the reference sensor and the error sensor. The reference signal and residual noise error signal are transmitted to the controller, which controls the broadband control branch and the narrowband control branch to perform calculations on the reference signal to obtain the total control signal. The controller is used to control the broadband control branch and the narrowband control branch. The residual noise error signal is used to update the parameters of the broadband control branch and the narrowband control branch. The broadband control branch is used to suppress continuous broadband background noise, and the narrowband control branch is used to suppress discrete narrowband peak noise. The main control signal is transmitted to the secondary sound source, which generates a control sound that cancels out the low-frequency noise of the air-cooled system, thus achieving synergistic suppression of the low-frequency noise of the air-cooled system. The active noise control component includes a reference sensor, an error sensor, a controller, and a secondary sound source.

[0007] According to one embodiment of the present invention, the step of transmitting air-cooled low-frequency noise into a passive sound-absorbing component and pre-processing the air-cooled low-frequency noise through a micro-perforated coupled coiled cavity sound-absorbing structure to obtain composite noise includes: The air-cooled low-frequency noise is emitted onto the micro-perforated plate, allowing the air-cooled low-frequency noise to enter the coiled cavity through the micro-perforations on the micro-perforated plate. The sound-absorbing structure formed by coupling the micro-perforated plate with the coiled cavity absorbs the low-frequency noise of air cooling, resulting in composite noise; The micro-perforated coupled coiled cavity sound-absorbing structure is constructed based on an electro-acoustic analogy method to build an equivalent impedance model. The air column in the micro-perforation is equivalent to acoustic mass, the thermal viscous loss of the micro-perforation wall and the inner wall of the coiled cavity is equivalent to acoustic resistance, and the closed back cavity is equivalent to acoustic capacitance. The total impedance of the micro-perforated coupled coiled cavity sound-absorbing structure meets the impedance matching requirements near the target frequency. The real part of the total impedance is close to the characteristic impedance of air, and the imaginary part is close to zero.

[0008] According to one embodiment of the present invention, the passive sound absorption component is disposed on the sound propagation path of the air outlet, the active noise control component is disposed in the open sound field of the air outlet, and the controller adopts a feedforward, multi-channel, wide and narrow band fusion control structure, and prioritizes noise control for the open sound field of a single air outlet.

[0009] According to one embodiment of the present invention, transmitting the reference signal and the residual noise error signal to the controller, and controlling the broadband control branch and the narrowband control branch to perform calculations on the reference signal to obtain the total control signal, includes: The reference signal and residual noise error signal are transmitted to the controller. The narrowband control branch uses the frequency self-tracking notch filter FxLMS algorithm to calculate the reference signal, track the discrete narrowband peak components in the reference signal, and obtain the narrowband control output and the dominant frequency estimation result. The reference signal and the dominant frequency estimation results are used as inputs to the broadband control branch. The variable step size normalized FxLMS algorithm with acoustic feedback cancellation is used to calculate the reference signal and the dominant frequency estimation results to obtain the broadband control output. The narrowband control output and the wideband control output are superimposed and fused in the time domain to obtain the total control signal.

[0010] According to one embodiment of the present invention, the step of using the frequency self-tracking notch filter FxLMS algorithm to operate on the reference signal, tracking the discrete narrowband peak components in the reference signal, and obtaining the narrowband control output and the dominant frequency estimation result includes: Obtain the short-time spectrum of the reference signal and construct a narrow-band search interval; Instantaneous main frequency estimation is performed within the search interval to obtain the instantaneous main frequency estimation result; The instantaneous dominant frequency estimation results are smoothed, and harmonic components are constructed. The orthogonal reference signal of the narrowband control branch is constructed based on the instantaneous main frequency estimation result and the harmonic components; The orthogonal narrowband reference signal is transmitted to the narrowband control filter for filtering to obtain the narrowband control output and the dominant frequency estimation result. The weight update of the narrowband control filter includes: The orthogonal reference signal of the narrowband control branch is transmitted to the secondary path estimation model for pre-filtering to obtain the narrowband filter reference vector; Using a fixed step size, the weights of the narrowband control filter are iteratively updated based on the residual noise error signal and the narrowband filter reference vector.

[0011] According to one embodiment of the present invention, the step-size normalized FxLMS algorithm with acoustic feedback cancellation is used to calculate the reference signal and the dominant frequency estimation results to obtain a broadband control output, including: The net reference signal is obtained by subtracting the feedback component from the reference signal, wherein the feedback component is estimated based on the acoustic feedback path model; Based on the dominant frequency estimation results, the corresponding spectral line components in the net reference signal are suppressed to obtain the broadband branch-specific reference signal; The broadband branch-specific reference signal is transmitted to the broadband control filter for filtering to obtain the broadband control output.

[0012] According to one embodiment of the present invention, the method further includes: The broadband tributary-specific reference signal is transmitted to the secondary path estimation model for pre-filtering to obtain the broadband filtered reference vector; The step size is normalized based on the instantaneous energy of the broadband filter reference vector to obtain the normalized step size. The power of the residual noise error signal is smoothed and estimated to obtain the error power estimation result; The step size is adaptively adjusted based on the error power estimation results to obtain a variable step size. The weights of the broadband controlled filter are iteratively updated based on the variable step size, residual noise error signal, and broadband filter reference vector.

[0013] Secondly, the present invention provides an active-passive fusion noise reduction system for low-frequency noise from air-cooled systems, the system comprising: The acquisition module is used to acquire air-cooled low-frequency noise and transmit it to a passive sound-absorbing component. The air-cooled low-frequency noise is pre-processed through a micro-perforated coupled coiled cavity sound-absorbing structure to obtain composite noise. The micro-perforated coupled coiled cavity sound-absorbing structure includes a micro-perforated plate, a coiled cavity, and a base plate. Multiple micro-holes are formed on the micro-perforated plate, through which the air-cooled low-frequency noise passes into the coiled cavity. The composite noise includes broadband noise and narrowband noise. The first processing module is used to transmit the composite noise to the active noise control component and acquire the reference signal of the composite noise and the residual noise error signal in the target area through the reference sensor and the error sensor. The second processing module is used to transmit the reference signal and the residual noise error signal to the controller, and control the broadband control branch and the narrowband control branch to perform calculations on the reference signal to obtain the total control signal. The controller is used to control the broadband control branch and the narrowband control branch. The residual noise error signal is used to update the parameters of the broadband control branch and the narrowband control branch. The broadband control branch is used to suppress continuous broadband background noise, and the narrowband control branch is used to suppress discrete narrowband peak noise. The third processing module is used to transmit the main control signal to the secondary sound source, so that the secondary sound source generates control sound that cancels out the low-frequency noise of the air-cooled system, thereby achieving synergistic suppression of the low-frequency noise of the air-cooled system. The active noise control component includes a reference sensor, an error sensor, a controller, and a secondary sound source.

[0014] Thirdly, the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the active-passive fusion noise reduction method for air-cooled low-frequency noise as described in the first aspect above.

[0015] Fourthly, the present invention provides a non-transitory computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the active-passive fusion noise reduction method for air-cooled low-frequency noise as described in the first aspect above.

[0016] Fifthly, the present invention provides a chip including a processor and a communication interface, the communication interface being coupled to the processor, the processor being used to run programs or instructions to implement the active-passive fusion noise reduction method for air-cooled low-frequency noise as described in the first aspect.

[0017] In a sixth aspect, the present invention provides a computer program product, including a computer program that, when executed by a processor, implements the active-passive fusion noise reduction method for low-frequency air-cooled noise as described in the first aspect above.

[0018] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

[0019] The present invention provides an active-passive fusion noise reduction method for low-frequency noise from air-cooled systems, which has the following advantages over existing technologies: 1. In the passive noise reduction section, the present invention adopts a micro-perforated coupled coiled cavity sound absorption structure, and combines it with an equivalent impedance model based on electro-acoustic analogy and a parameterized design method, which can achieve efficient absorption of target low-frequency noise under the constraints of limited space and limited thickness, thereby taking into account the noise reduction effect, structural compactness and ventilation and heat dissipation requirements.

[0020] 2. In the active noise reduction section, the present invention adopts a wide and narrow band fusion control architecture. Through the coordinated work of the wide band control branch and the narrow band control branch, continuous wide band background noise and discrete narrow band peak noise are suppressed respectively. Combined with the dynamic notch separation at the reference end, the shared error signal update and the time domain superposition output strategy, the overall control capability of composite noise is improved.

[0021] 3. This invention organically combines passive sound absorption with active control. The passive noise reduction part first weakens the target low-frequency noise and reduces the burden of active control. Then, the active noise reduction part finely suppresses the residual noise. Thus, while ensuring system stability and engineering feasibility, it achieves efficient active and passive noise reduction for wind-cooled composite noise. Attached Figure Description

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a flowchart illustrating the active and passive fusion noise reduction method for low-frequency air-cooled noise provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the working process of the active noise control component provided in an embodiment of the present invention; Figure 3 This is a flowchart of the wideband and narrowband fusion control algorithm provided in an embodiment of the present invention; Figure 4 This is a flowchart illustrating the overall design of the active noise control software provided in this embodiment of the invention. Figure 5 This is a flowchart of the active and passive fusion noise reduction method provided in the embodiments of the present invention; Figure 6 This is a schematic diagram of the active and passive fusion noise reduction system for air-cooled low-frequency noise provided in an embodiment of the present invention; Figure 7 This is a schematic diagram of the structure of the electronic device provided in an embodiment of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0024] The terms "first," "second," etc., used in the specification and claims of this invention are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0025] The active and passive fusion noise reduction method for air-cooled low-frequency noise, the active and passive fusion noise reduction system for air-cooled low-frequency noise, the electronic device, and the readable storage medium provided by the present invention will be described in detail below with reference to the accompanying drawings and through specific embodiments and application scenarios.

[0026] Among them, the active and passive fusion noise reduction method for low-frequency noise from air cooling can be applied to the terminal, and can be executed by the hardware or software in the terminal.

[0027] The terminal includes, but is not limited to, portable communication devices such as mobile phones or tablets with touch-sensitive surfaces (e.g., touchscreen displays and / or touchpads). It should also be understood that, in some embodiments, the terminal may not be a portable communication device, but rather a desktop computer with touch-sensitive surfaces (e.g., touchscreen displays and / or touchpads).

[0028] The following embodiments describe a terminal including a display and a touch-sensitive surface. However, it should be understood that the terminal may include one or more other physical user interface devices such as a physical keyboard, mouse, and joystick.

[0029] The active-passive fusion noise reduction method for air-cooled low-frequency noise provided in this embodiment of the invention can be executed by an electronic device or a functional module or entity in an electronic device that can implement the active-passive fusion noise reduction method for air-cooled low-frequency noise. The electronic devices mentioned in this embodiment of the invention include, but are not limited to, mobile phones, tablets, computers, cameras, and wearable devices. The active-passive fusion noise reduction method for air-cooled low-frequency noise provided in this embodiment of the invention will be described below using an electronic device as the execution subject.

[0030] Figure 1 This is a flowchart illustrating the active-passive fusion noise reduction method for low-frequency air-cooled noise provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the active and passive fusion noise reduction method for low-frequency noise from air cooling includes steps 110, 120, 130 and 140.

[0031] Step 110: Obtain the air-cooled low-frequency noise and transmit it into the passive sound-absorbing component. Preprocess the air-cooled low-frequency noise through the micro-perforated coupled coiled cavity sound-absorbing structure to obtain composite noise. The micro-perforated coupled coiled cavity sound-absorbing structure includes a micro-perforated plate, a coiled cavity, and a base plate. The micro-perforated plate has multiple micro-holes. The air-cooled low-frequency noise enters the coiled cavity after passing through the micro-holes. The composite noise includes broadband noise and narrowband noise. It is easy to understand that, for low-frequency noise, the passive noise reduction part adopts a micro-perforated coupled coiled cavity sound-absorbing structure. Through a parametric design method for low-frequency composite noise, the target frequency band and design constraints of the passive noise reduction are first determined. That is, based on the target frequency range of the noise to be suppressed, combined with the installation space, structural thickness, ventilation and heat dissipation requirements, and processing conditions, the design boundary of the passive noise reduction structure is determined. Then, based on the characteristics of low-frequency noise wavelength and the limited absorption efficiency of traditional thin sound-absorbing materials, a passive noise reduction base structure suitable for low-frequency absorption is selected, preferably a micro-perforated coupled coiled cavity structure, to improve the absorption capacity of target frequency noise within a limited thickness. Further, an acoustic design model of the base structure is established, and an equivalent impedance model of the coupling between the micro-perforated plate and the coiled cavity is constructed based on the electro-acoustic analogy method. On this basis, key design parameters such as the thickness of the micro-perforated plate, the micro-pore diameter, the cavity height, the cavity width, and the effective propagation length of the coiled channel are determined. By adjusting the key design parameters, the structure meets the impedance matching requirements near the target frequency, thereby improving the sound absorption efficiency in the target frequency band.

[0032] Furthermore, in the passive noise reduction section, the method for establishing the equivalent impedance model based on electro-acoustic analogy includes: performing acoustic equivalence on the micro-perforated plate, the coiled cavity, and the closed back cavity in the micro-perforated coupled coiled cavity structure; equivalence the air column in the micro-perforations to acoustic mass, equivalence the thermal viscous loss generated by the micro-perforation wall and the inner wall of the coiled cavity under the action of sound waves to acoustic resistance, and equivalence the closed back cavity to acoustic capacitance; establishing equivalent impedance models for the micro-perforated plate and the coiled cavity respectively, and coupling the equivalent impedance of the micro-perforated plate with the equivalent impedance of the coiled cavity to obtain the total equivalent impedance of the passive noise reduction structure; and establishing the correspondence between the structural surface impedance and sound absorption performance based on the relationship between the total equivalent impedance and the air characteristic impedance to characterize the sound absorption characteristics of the passive noise reduction structure in the target frequency band.

[0033] Furthermore, in the passive noise reduction section, the method for adjusting key design parameters to ensure the structure meets impedance matching requirements near the target frequency includes: selecting the thickness of the micro-perforated plate, the diameter of the micro-pores, the cavity height, the cavity width, and the effective propagation length of the coiled channel as key design parameters under predetermined target noise reduction frequency band, total structural thickness constraints, and installation boundary conditions; calculating the surface impedance response of the passive noise reduction structure near the target frequency under different combinations of key design parameters based on the established equivalent impedance model; adjusting the key design parameters in combination to gradually bring the real part of the total impedance of the passive noise reduction structure closer to the characteristic impedance of air, and the imaginary part closer to zero, so that the structure meets impedance matching requirements near the target frequency; and determining the corresponding combination of key design parameters as the design result of the passive noise reduction structure after meeting the impedance matching requirements, thereby improving the sound absorption efficiency in the target frequency band.

[0034] Furthermore, the passive noise reduction section also includes a cell parameter optimization method based on a genetic algorithm. The method determines the parameters to be optimized for the passive noise reduction structure based on the target noise reduction frequency band, structural thickness constraints, and the established equivalent impedance model. These parameters are then encoded and an initial population is generated. The sound absorption performance of each parameter combination at the target frequency is calculated based on the equivalent impedance model, and the difference between the sound absorption coefficient at the target frequency and the preset target sound absorption coefficient is used as the fitness function. Selection, crossover, and mutation operations are performed on the population individuals according to the fitness function to obtain a new generation of parameter combinations. The fitness evaluation and population update process is repeated until a preset number of iterations is reached or the convergence condition is met. The cell structure parameters that optimize the sound absorption performance at the target frequency are output as the optimized design result of the passive noise reduction structure. Through this method, passive sound absorption structure parameters suitable for the target frequency band can be obtained under multi-parameter coupling and nonlinear constraints, improving the design efficiency and accuracy of the passive noise reduction section.

[0035] In one embodiment, the passive noise reduction section of the present invention employs a parametric design method for low-frequency noise, including the following steps: Step S1: Determine the target frequency band of the noise, and in combination with the installation space, structural thickness, ventilation and heat dissipation requirements and processing conditions in the actual application, determine the design boundary conditions of the passive noise reduction structure.

[0036] The target frequency band is preferably the low-frequency band that needs to be suppressed in the noise of the air-cooled system, so as to ensure that the subsequent structural design can effectively absorb the target frequency.

[0037] Step S2: Select a passive noise reduction base structure suitable for low-frequency absorption.

[0038] Preferably, the passive noise reduction base structure adopts a micro-perforated coupled coiled cavity structure, which allows incident sound waves to enter the internal coiled channel through the micro-perforations, extending the propagation path within a limited thickness and enhancing the low-frequency dissipation capability, thereby meeting the low-frequency sound absorption requirements.

[0039] The passive noise reduction section employs a parametric design method for low-frequency composite noise, including: Determine the target frequency band and design constraints for passive noise reduction; Select a passive noise reduction base structure suitable for low-frequency absorption based on the installation space, structural thickness, and ventilation and heat dissipation requirements; An acoustic design model for the basic structure was established, and an equivalent impedance model of the coupling between the micro-perforated plate and the coiled cavity was constructed based on the electro-acoustic analogy method. Key design parameters such as the thickness of the micro-perforated plate, the diameter of the micropores, the height of the cavity, the width of the cavity, and the effective propagation length of the coiled channel are determined. By adjusting the key design parameters, the structure meets the impedance matching requirements near the target frequency, thereby improving the sound absorption efficiency in the target frequency band.

[0040] Step S3: Establish the equivalent impedance model of the basic structure based on the electro-acoustic analogy method to obtain the correspondence between the surface impedance of the structure and the sound absorption performance.

[0041] In this study, the air column in the micro-perforation is equivalent to acoustic mass, the thermal viscous loss generated by the micro-perforation wall and the inner wall of the coiled cavity is equivalent to acoustic resistance, the closed back cavity is equivalent to acoustic capacitance, and the total equivalent impedance model of the entire passive noise reduction structure is established by coupling the impedance of the micro-perforated plate with the impedance of the coiled cavity.

[0042] Step S4: Determine the key design parameters of the passive noise reduction structure.

[0043] Key design parameters include the thickness of the micro-perforated plate, the diameter of the micropores, the cavity height, the cavity width, and the effective propagation length of the coiled channel. By adjusting these key design parameters, the structure meets impedance matching requirements near the target frequency, thereby improving the sound absorption efficiency within the target frequency band. Specifically, by analyzing the variation of the total impedance of the structure under different parameter combinations, the real part of the total impedance is gradually made to approach the characteristic impedance of air, and the imaginary part is gradually made to approach zero, in order to obtain a better sound absorption effect.

[0044] Step S5: Perform joint design of each key parameter to ensure that the parameters are matched with each other and avoid deviation in sound absorption performance caused by adjusting a single parameter.

[0045] Preferably, under the condition of satisfying the total structural thickness constraint, the relevant parameters of the micro-perforated plate, cavity and coiled channel are synergistically optimized so that the total structural impedance reaches an ideal matching state near the target frequency.

[0046] The method for adjusting key design parameters in a micro-perforated coupled disc-wound cavity sound-absorbing structure to ensure impedance matching requirements near the target frequency includes the following steps: Under the predetermined target noise reduction frequency band, total structural thickness constraints, and installation boundary conditions, the micro-perforated plate thickness, micro-pore diameter, cavity height, cavity width, and effective propagation length of the coiled channel are selected as key design parameters. Based on the established equivalent impedance model, the surface impedance response of the passive noise reduction structure near the target frequency is calculated under different combinations of key design parameters. By jointly adjusting key design parameters, the real part of the total impedance of the passive noise reduction structure gradually approaches the characteristic impedance of air, and the imaginary part gradually approaches zero, so that the structure meets the impedance matching requirements near the target frequency. After meeting the impedance matching requirements, the corresponding key design parameter combination is determined as the design result of the passive noise reduction structure to improve the sound absorption efficiency in the target frequency band.

[0047] A method for establishing an equivalent impedance model based on electro-acoustic analogy in a micro-perforated coupled disc-wound cavity sound-absorbing structure includes the following steps: The micro-perforated plate, the coiled cavity, and the closed back cavity in the micro-perforated coupled coiled cavity structure are acoustically equivalent. The air column in the micro-perforation is equivalent to the acoustic mass, the thermal viscous loss generated by the micro-perforation wall and the inner wall of the coiled cavity under the action of sound waves is equivalent to the acoustic resistance, and the closed back cavity is equivalent to the acoustic capacity. The equivalent impedance models of the micro-perforated plate and the coiled cavity are established respectively, and the equivalent impedance of the micro-perforated plate and the equivalent impedance of the coiled cavity are coupled to obtain the total equivalent impedance of the passive noise reduction structure. Based on the relationship between total equivalent impedance and air characteristic impedance, a correspondence between structural surface impedance and sound absorption performance is established to characterize the sound absorption characteristics of passive noise reduction structures in the target frequency band.

[0048] Step S6: Optimize the unit cell structural parameters using a genetic algorithm.

[0049] Specifically, to improve the efficiency and accuracy of parameter design, the parameters to be optimized are determined based on the target noise reduction frequency band, thickness constraints and equivalent impedance model. The parameters to be optimized are encoded to generate an initial population, and the sound absorption performance at the target frequency is used as the fitness evaluation basis. The population is continuously updated through selection, crossover and mutation operations until the optimal parameter combination that meets the preset conditions is obtained, which is the design result of the passive noise reduction structure.

[0050] The method for optimizing unit cell parameters based on genetic algorithm in the micro-perforated coupled disc-wound cavity sound-absorbing structure includes the following steps: Based on the target noise reduction frequency band, structural thickness constraints, and the established equivalent impedance model, the parameters to be optimized for the passive noise reduction structure are determined. The parameters to be optimized are encoded to generate an initial population; The sound absorption performance of each parameter combination at the target frequency is calculated based on the equivalent impedance model, and the difference between the sound absorption coefficient at the target frequency and the preset target sound absorption coefficient is used as the fitness function. Based on the fitness function, selection, crossover, and mutation operations are performed on individuals in the population to obtain a new generation of parameter combinations; Repeat the fitness assessment and population update process until the preset number of iterations is reached or the convergence condition is met; The output is the unit cell structure parameters that optimize the sound absorption performance at the target frequency, serving as the result of the optimized design of the passive noise reduction structure.

[0051] Step S7: Determine the arrangement of the passive noise reduction structure.

[0052] The arrangement should meet the requirement of prioritizing the reduction of noise components in the target frequency band, so that the passive noise reduction structure is arranged along the main sound propagation path, so that the original noise first passes through the passive noise reduction structure and achieves pre-absorption of the target frequency band during propagation, providing a low residual noise basis for subsequent active noise reduction.

[0053] Step 120: Transmit the composite noise to the active noise control component, and acquire the reference signal of the composite noise and the residual noise error signal in the target area through the reference sensor and the error sensor; In some embodiments, the passive sound-absorbing component is disposed on the sound propagation path of the air outlet, the active noise control component is disposed in the open sound field of the air outlet, and the controller adopts a feedforward, multi-channel, wide and narrow band fusion control structure, prioritizing noise control for the open sound field of a single air outlet.

[0054] The passive sound absorption component works in conjunction with the active noise control component. The passive sound absorption component is used to reduce the propagation energy of noise in the target frequency band and actively control the load, while the active noise control component is used to adaptively compensate and suppress the residual broadband noise and narrowband noise after passive sound absorption, thereby improving the overall noise reduction effect and reducing the output demand of secondary sound sources.

[0055] Step 130: The reference signal and residual noise error signal are transmitted to the controller, and the broadband control branch and the narrowband control branch are controlled to perform calculations on the reference signal to obtain the total control signal. The controller is used to control the broadband control branch and the narrowband control branch. The residual noise error signal is used to update the parameters of the broadband control branch and the narrowband control branch. The broadband control branch is used to suppress continuous broadband background noise, and the narrowband control branch is used to suppress discrete narrowband peak noise. Step 140: Transmit the main control signal to the secondary sound source, so that the secondary sound source generates a control sound that cancels out the low-frequency noise of the air-cooled system, thereby achieving synergistic suppression of the low-frequency noise of the air-cooled system. The active noise control component includes a reference sensor, an error sensor, a controller, and a secondary sound source.

[0056] In one implementation, the active noise reduction method employs a wide-band and narrow-band fusion active noise reduction method, including the following steps: S1. Acquire the reference signal of the original noise and the residual noise error signal in the target area; S2. Perform operations on the wideband control branch and the narrowband control branch in parallel on the reference signal, wherein the wideband control branch is used to suppress continuous wideband noise components and the narrowband control branch is used to suppress discrete narrowband noise components. S3. Based on the dominant frequency estimation results obtained from the narrowband control branch, suppress the components near the corresponding spectral lines in the reference signal to form a dedicated reference input for the broadband control branch. S4. Obtain the broadband control output and the narrowband control output respectively, and superimpose and fuse the two in the time domain to generate the total control signal; S5. Output the main control signal to the secondary sound source, so that the secondary sound source generates control sound that cancels out the original noise, thereby achieving synergistic suppression of wide and narrow band composite noise. S6. Update the parameters of the broadband control branch and the narrowband control branch according to the error signal to complete the broadband and narrowband fusion active noise reduction.

[0057] In another implementation, the active noise reduction component is designed as an active noise control assembly to address the composite noise. This assembly includes a reference sensor, an error sensor, a secondary sound source, a controller, an audio acquisition and output circuit, a secondary path model, and an acoustic feedback path model. The reference sensor acquires the original noise reference signal, the error sensor acquires the residual noise signal, and the controller outputs a control signal based on the reference and error signals to drive the secondary sound source to emit a control sound with the opposite phase to the original noise. The controller includes a broadband control branch and a narrowband control branch. The broadband control branch suppresses continuous broadband background noise, and the narrowband control branch suppresses discrete narrowband peak noise. The outputs of the two branches are superimposed to jointly drive the secondary sound source, thereby achieving active suppression of the wind-cooled composite noise.

[0058] In some embodiments, the variable step-size normalized FxLMS algorithm with acoustic feedback cancellation is used to calculate the reference signal and the dominant frequency estimation results to obtain a broadband control output, including: The net reference signal is obtained by subtracting the feedback component from the reference signal, wherein the feedback component is estimated based on the acoustic feedback path model; Based on the dominant frequency estimation results, the corresponding spectral line components in the net reference signal are suppressed to obtain the broadband branch-specific reference signal; The broadband branch-specific reference signal is transmitted to the broadband control filter for filtering to obtain the broadband control output.

[0059] In some embodiments, the method further includes: The broadband tributary-specific reference signal is transmitted to the secondary path estimation model for pre-filtering to obtain the broadband filtered reference vector; The step size is normalized based on the instantaneous energy of the broadband filter reference vector to obtain the normalized step size. The power of the residual noise error signal is smoothed and estimated to obtain the error power estimation result; The step size is adaptively adjusted based on the error power estimation results to obtain a variable step size. The weights of the broadband controlled filter are iteratively updated based on the variable step size, residual noise error signal, and broadband filter reference vector.

[0060] Furthermore, the broadband control branch preferably employs the variable step-size normalized FxLMS algorithm with acoustic feedback cancellation. This algorithm estimates the feedback component from the secondary sound source to the reference sensor based on the acoustic feedback path model and subtracts it from the reference signal to obtain the net reference signal; then, it pre-filters the net reference signal based on the secondary path model; the step size is normalized and adjusted according to the energy of the filtered reference signal; and the step size is adaptively adjusted according to the error energy change to balance the system convergence speed and steady-state error, thereby improving the control performance of the broadband control branch against continuous broadband background noise and the system stability.

[0061] In some embodiments, the step of using the frequency self-tracking notch filter FxLMS algorithm to operate on the reference signal, tracking the discrete narrowband peak components in the reference signal, and obtaining the narrowband control output and dominant frequency estimation results includes: Obtain the short-time spectrum of the reference signal and construct a narrow-band search interval; Instantaneous main frequency estimation is performed within the search interval to obtain the instantaneous main frequency estimation result; The instantaneous dominant frequency estimation results are smoothed, and harmonic components are constructed. The orthogonal reference signal of the narrowband control branch is constructed based on the instantaneous main frequency estimation result and the harmonic components; The orthogonal narrowband reference signal is transmitted to the narrowband control filter for filtering to obtain the narrowband control output and the dominant frequency estimation result. The weight update of the narrowband control filter includes: The orthogonal reference signal of the narrowband control branch is transmitted to the secondary path estimation model for pre-filtering to obtain the narrowband filter reference vector; Using a fixed step size, the weights of the narrowband control filter are iteratively updated based on the residual noise error signal and the narrowband filter reference vector.

[0062] Furthermore, the narrowband control branch preferably employs the frequency self-tracking notch filter FxLMS algorithm. This algorithm constructs a narrowband reference signal synchronized with the target discrete spectrum by performing online frequency tracking of the tonality components in the reference signal, and directionally suppresses discrete narrowband peak noise near the fundamental frequency and its harmonics, thereby improving the adaptability of the narrowband control branch under conditions of main frequency drift or operating condition changes.

[0063] Furthermore, a dynamic notch filtering strategy is employed at the reference end. Using the dominant frequency and harmonics estimated online by the narrowband control branch, narrowband components near corresponding frequencies in the net reference signal are suppressed, constructing a dedicated reference signal for the broadband control branch. Moreover, the broadband and narrowband control branches share the same error signal for parameter updates, and the outputs of the two branches are directly superimposed in the time domain to serve as the secondary sound source driving signal. Through this method, coordinated operation between the broadband and narrowband control branches can be achieved, avoiding mutual interference at the reference input, while simultaneously improving the synergistic control effect on continuous broadband noise and discrete narrowband peak noise.

[0064] In this invention, the passive noise reduction component and the active noise reduction component are not independent of each other, but rather form a combined active-passive noise reduction system. The passive noise reduction component prioritizes the absorption of target low-frequency noise, reducing the acoustic energy level of the target frequency band in the original noise and lessening the control burden on the active noise reduction component. The active noise reduction component then finely suppresses the residual broadband noise and narrowband peak noise that remain after passive absorption. Through the organic combination of these two components, the overall noise reduction effect can be improved without significantly affecting the ventilation and heat dissipation performance and structural dimensions of the air-cooled system, and the limitations of a single passive noise reduction method or a single active noise reduction method in engineering applications can be overcome.

[0065] Figure 2 is a schematic diagram of the operation process of the active noise control component provided in an embodiment of the present invention, as follows: Figure 2 As shown, it includes the following steps: Step S1: Reference Signal Acquisition The original noise reference signal is acquired using a reference microphone group located at the front end of the noise propagation. The reference microphone group includes a first reference microphone Ref1 and a second reference microphone Ref2. The acquired reference signal is amplified, filtered, and impedance matched by the front-end conditioning module before being input into the data acquisition and processing system.

[0066] Step S2: Error signal acquisition.

[0067] Residual noise error signals are collected using an error microphone group located near the target control area. The error microphone group includes a first error microphone Err1 and a second error microphone Err2. The error signals, along with the reference signals, are input into the data acquisition and processing system for subsequent control algorithm calculations and parameter updates.

[0068] Step S3: Calculate the control signal.

[0069] In the data acquisition and processing system, the analog-to-digital converter (ADC) converts the reference signal and the error signal into digital signals. The digital signal processor (DSP) calculates the inverse control signal in real time based on the reference signal, the error signal, and a preset active noise control algorithm. The digital-to-analog converter (DAC) converts the inverse control signal into an analog control signal for output.

[0070] Step S4: Output noise reduction signal.

[0071] The analog control signal output from the DAC is input to the power amplifier module, and after power amplification, it drives the noise-canceling speaker group to work. The noise-canceling speaker group includes a first noise-canceling speaker Spk1 and a second noise-canceling speaker Spk2. The noise-canceling speaker group emits a secondary sound wave that is out of phase with the original noise, so that it interferes with and cancels out the original noise in the target area.

[0072] Step S5: Feedback Update and Iterative Control.

[0073] The error microphone group detects the residual noise after active control in real time and feeds the detection results back to the digital signal processor (DSP). The DSP iteratively corrects the control parameters based on the updated error signal and continuously adjusts the output control signal to achieve stable active suppression of composite noise in the target area.

[0074] Preferably, by configuring dual reference microphones, dual error microphones, and dual noise-canceling speakers, the accuracy of reference signal acquisition, the accuracy of residual noise detection, and the control of sound field coverage can be improved, thereby enhancing the active noise reduction effect under open sound field conditions.

[0075] Figure 3 This is a flowchart of the broadband and narrowband fusion control algorithm provided in an embodiment of the present invention, as shown below. Figure 3 As shown, this embodiment also provides a broadband and narrowband integrated active noise control method, including a narrowband control branch, a broadband control branch, an acoustic feedback cancellation stage, and a secondary path compensation stage. The system input reference signal is x(n), which forms the target noise d(n) after passing through the primary path P(z). The control signal output by the secondary sound source propagates through the secondary path S(z) to form the secondary sound source. The residual error signal e(n) is then superimposed on the target noise at the error end. This residual error signal serves as the basis for updating the parameters of both the broadband and narrowband control branches, enabling coordinated control of the composite noise. The broadband-narrowband fusion active noise control method includes the following steps:

[0076] Step 101: Design a narrowband control branch to suppress discrete narrowband peak noise.

[0077] Unlike traditional narrowband control methods that rely on speed sensors or preset fixed notch frequencies, the narrowband branch in this embodiment uses the frequency self-tracking notch FxLMS algorithm. Instead of pre-fixing the target frequency, it performs online frequency estimation on the net reference signal collected by the reference microphone to obtain the actual frequency position of the dominant discrete spectral line under the current operating conditions.

[0078] Step 101 includes the following sub-steps: Step S11: Obtain the short-time spectrum of the reference signal and construct a narrowband search interval.

[0079] Let the short-time spectrum obtained from the reference microphone signal during the analysis of the k-th frame be... Based on the noise spectrum characteristics, the dominant narrowband peak is located around 400Hz, therefore the estimated dominant frequency from the previous frame can be used. Using this as the center, construct the narrowband search interval for the current frame:

[0080]

[0081] in, This represents the frequency search half-bandwidth.

[0082] Step S12: Complete the instantaneous main frequency estimation within the search interval.

[0083] Within the search interval, the frequency point with the largest short-time spectral amplitude is taken as the estimated instantaneous dominant frequency of the current frame, i.e.:

[0084] This step allows us to obtain the instantaneous frequency position of the dominant narrowband spectral line corresponding to the current operating conditions.

[0085] Step S13: Smooth the instantaneous dominant frequency estimation results and construct the harmonic components.

[0086] Considering that the instantaneous frequency estimation result may be affected by spectral fluctuations, in order to improve the stability of the subsequent control process, the instantaneous main frequency estimate is subjected to first-order smoothing to obtain the smoothed main frequency estimate:

[0087] in, This is the smoothing coefficient. Furthermore, its harmonic components can be constructed based on the obtained estimated dominant frequency:

[0088]

[0089] The above processing can reduce the adverse effects of frequency estimation jitter on narrowband control stability.

[0090] Step S14: Construct the quadrature reference signal of the narrowband control branch based on the main frequency and its harmonics.

[0091] In obtaining and Then, the orthogonal reference signal required to construct the narrowband control branch is specifically expressed as follows:

[0092] in, The sampling period is The sampling frequency is [value]. The above orthogonal signals can be further combined to form the reference input vector for the narrowband control branch:

[0093]

[0094] Step S15: Construct a narrowband control filter and calculate the narrowband branch output.

[0095] Let the weight vector of the narrowband controlled filter be:

[0096] The output of the narrowband control branch at time n can be expressed as:

[0097] When the narrowband subsystem operates alone, its error signal can be expressed as:

[0098] in, This represents the narrowband target noise component. This indicates the transitive characteristics of secondary paths.

[0099] Step S16: Perform secondary path pre-filtering on the narrowband reference vector.

[0100] Similar to the broadband control branch, to compensate for the impact of the secondary path on the control signal, the narrowband reference vector also needs to be processed by the secondary path estimation model before being used for weight updates. The pre-filtering process yields the narrowband filter reference vector:

[0101] This step allows the parameter updates of the narrowband control filter to more accurately reflect the actual secondary path characteristics.

[0102] Step S17: Iteratively update the weights of the narrowband control filter using a fixed step size.

[0103] Considering the low parameter dimension of narrowband branches and the relatively well-defined target frequency, this embodiment employs a small fixed step size to ensure update stability during frequency tracking. The weights of the narrowband control filter are iteratively updated, i.e.:

[0104] As shown in the above equation, the narrowband control branch can adjust the amplitude and phase of the control signal online by estimating the fundamental frequency in real time and constructing the corresponding orthogonal reference vector, thereby achieving directional suppression of discrete spectral lines near the fundamental frequency and its harmonics. Compared with the fixed-frequency notch control method, this method can better adapt to spectral drift caused by wind turbine speed fluctuations, thus improving the frequency tracking capability, control accuracy, and system stability of the narrowband control branch under varying operating conditions.

[0105] Step 102: Based on the standard FxLMS algorithm, an acoustic feedback cancellation module is introduced to design a variable step size normalized FxLMS algorithm with acoustic feedback cancellation.

[0106] Step 102 includes the following sub-steps: Step S21: Construct the actual signal acquired by the reference microphone and perform acoustic feedback component estimation.

[0107] Let the actual signal collected by the reference microphone be... It consists of a reference component related to the original noise. and the feedback component coupled back to the reference end from the secondary sound source. Superposition, that is:

[0108] Let the acoustic feedback path estimation model be... The output of the broadband controller is Then the estimated value of the feedback component can be expressed as:

[0109] The above feedback component estimation provides a basis for subsequent reference signal purification.

[0110] Step S22: Perform acoustic feedback cancellation on the reference signal to obtain a net reference signal.

[0111] Based on the estimated feedback components, the actual signal acquired by the reference microphone is subtracted to obtain the net reference signal actually used by the broadband control branch. :

[0112] in, This is the reference signal actually used in the broadband control branch. The net reference signal is further constructed into a reference input vector of length L:

[0113]

[0114] This step reduces the interference of secondary sound sources on the reference input and improves the correlation between the reference signal and the original broadband noise.

[0115] Step S23: Generate a wideband control output based on the net reference signal.

[0116] Let the weight vector of the broadband controlled filter be:

[0117] The output of the broadband control branch can then be expressed as:

[0118] The broadband control output Used to drive secondary sound sources to generate control sound that cancels out continuous broadband noise components.

[0119] Step S24: Pre-filter the net reference signal using the secondary path estimation model.

[0120] Considering that the secondary path S(z) affects the gradient direction, a secondary path estimation model needs to be introduced. The net reference signal is pre-filtered. Let the pre-filtered scalar signal be:

[0121]

[0122] And construct the filter reference vector:

[0123] Meanwhile, let the original broadband noise component at the error microphone be... Then the residual error signal of the broadband control branch is:

[0124] In the formula, the control sound component formed at the error point after the broadband control signal passes through the secondary path is:

[0125] The above pre-filtering process allows the weight update direction to more accurately reflect the actual secondary path characteristics.

[0126] Step S25: Introduce an input energy normalization mechanism to update the weights of the broadband control filter.

[0127] In the classic FxLMS algorithm, the weight update formula is:

[0128] in, The step size is fixed. Since a fixed step size makes it difficult to simultaneously ensure convergence speed and steady-state accuracy under different operating conditions, this embodiment further introduces an input energy normalization mechanism, resulting in the normalized FxLMS update formula:

[0129]

[0130] in, To prevent regularization terms with excessively small denominators, This represents the instantaneous energy of the filter reference vector. After normalization, the algorithm's sensitivity to changes in the reference signal amplitude is significantly reduced, which is beneficial for improving the stability and robustness of the broadband control branch under different operating conditions.

[0131] Step S26: Introduce an error energy-driven variable step size mechanism to complete the variable step size normalized FxLMS update.

[0132] To balance initial convergence speed and steady-state residuals, the error power is first estimated using exponential smoothing:

[0133] in, The smoothing coefficient is used. Then, a variable step size function is constructed based on the error energy:

[0134]

[0135] in, and These are the lower and upper limits of the step size, respectively, and c is a constant that adjusts the sensitivity of the step size change. When the error is large, Towards Approximating to accelerate convergence; after the system enters steady state, Automatic reduction is used to suppress steady-state fluctuations. Therefore, the final update formula for the variable step-size normalized FxLMS of the broadband branch is:

[0136]

[0137] Through the above steps, the broadband control branch simultaneously achieves acoustic feedback elimination, secondary path compensation, input energy normalization, and error energy-driven variable step size adjustment, which can better adapt to the amplitude fluctuations and time-varying characteristics of continuous broadband noise under actual operating conditions, thereby improving the system's convergence speed, steady-state control accuracy, and operational stability.

[0138] Step 103: Collaboratively suppress the continuous broadband noise floor and discrete narrowband peak in the composite noise. This embodiment provides a broadband-narrowband fusion control algorithm.

[0139] Step 103 includes the following sub-steps: Step S31: Construct the net reference signal and obtain the narrowband branch main frequency estimation results.

[0140] First, the original reference signal is acquired by the reference microphone, and then the net reference signal is obtained after acoustic feedback cancellation. Simultaneously, the narrowband branch performs online frequency estimation on the net reference signal to obtain the estimated main frequency value within the current analysis frame. and frequency doubling estimates The dominant frequency estimation result serves as the control parameter for subsequent dynamic notch separation, used to determine the positions of discrete spectral lines that need to be suppressed from the broadband reference.

[0141] Step S32: Perform dynamic notch separation at the reference end to construct a dedicated reference input for the broadband branch.

[0142] To reduce repetitive learning at discrete peak frequencies in the broadband branch, the dominant frequency and harmonics obtained from online estimation of the narrowband branch are used in the net reference signal. Introducing a dynamic notch operator {.}, suppressing narrowband components near the corresponding frequency, yields a dedicated reference signal for the broadband branch. , can be represented as:

[0143] in, This step establishes a narrowband suppression bandwidth. Through this process, the broadband branch is primarily driven by the continuous broadband noise floor, while the discrete narrowband peak is handled by the narrowband branch, thereby reducing parameter competition between the two branches near the target frequency.

[0144] Step S33: Construct the wideband branch input vector and perform filtered-x processing.

[0145] The broadband branch-specific reference signal Construct the input vector:

[0146] Then through the secondary path estimation model Pre-filtering yields the broadband filter reference vector:

[0147] Where L is the length of the broadband control filter. This step is used to compensate for the influence of secondary paths on the gradient direction, so as to ensure the effectiveness of broadband branch weight updates.

[0148] Step S34: Calculate the control outputs of the broadband branch and the narrowband branch respectively, and update the parameters by sharing the same error signal.

[0149] Within the fusion framework, both broadband and narrowband branches use the same error sensor output. As an evaluation metric and update basis, the broadband branch weight update formula is:

[0150]

[0151] in, For broadband branch variable step size, This is a regularization term. The corresponding broadband control output is:

[0152]

[0153] The narrowband branch still uses orthogonal reference signals to construct the control output, and its output can be expressed as:

[0154] And updated by the same error signal:

[0155] in, For narrowband reference vectors, This is the result of pre-filtering the narrowband reference vector using the secondary path estimation model. Fixed step size for narrowband branches.

[0156] Step S35: Perform time-domain superposition at the output to form the final control signal.

[0157] Broadband branch output and narrowband branch output The secondary speaker driving signal is obtained by directly superimposing the signals in the time domain. :

[0158] The driving signal, after being converted from digital to analog and amplified, drives the secondary sound source to emit a control sound, thereby simultaneously suppressing continuous broadband noise floor and discrete narrowband peaks.

[0159] Step S36: Calculate the residual error of the fusion control system and complete the closed-loop iteration.

[0160] Let the original composite noise at the error point be... The residual error of the fusion control system is:

[0161] Where S(z) is the secondary path transfer function. The residual error... On the one hand, it reflects the overall noise reduction effect after the coordinated control of the broadband and narrowband branches; on the other hand, it simultaneously feeds back to both branches as the basis for weight updates. Through the above steps, the fusion control system can combine the overall suppression capability of the broadband branch for continuous broadband background noise with the directional suppression capability of the narrowband branch for discrete spectral lines within the same single-channel feedforward control framework, thereby achieving coordinated control of broadband and narrowband composite noise.

[0162] Figure 4 This is a flowchart illustrating the overall design of the active noise control software provided in this embodiment of the invention. This embodiment also provides a system operation method based on an embedded digital signal processing platform, such as... Figure 4 As shown. The overall system consists of an initialization and configuration phase and a control algorithm execution phase. After system startup, the initialization and configuration phase begins first. This phase includes three parts: system initialization, audio link initialization, and control initialization. System initialization is used to configure the main control processor's clock, interrupts, and pin multiplexing settings to establish the basic hardware environment required for the control system's operation. Audio link initialization is used to configure the audio data acquisition and transmission channels, including the multi-channel audio serial port McASP, the direct memory access module DMA, and the audio codec AIC3106, enabling reference signals, error signals, and control signals to be transmitted in real time according to a predetermined sampling rate and data format. Control initialization is used to load the secondary path model, acoustic feedback path model, and initial parameters of the control filter, thereby providing initial conditions for the subsequent real-time operation of the active noise control algorithm.

[0163] After initial configuration is complete, the system enters the control algorithm execution phase. In this phase, the reference sensor first acquires the original noise reference signal in real time and sends it to the controller; the error sensor simultaneously acquires the residual noise signal within the target area and inputs it to the controller as an error signal. The controller executes a preset active noise control algorithm based on the reference signal and the error signal, calculates the anti-noise control signal in real time, and outputs the control signal to the secondary sound source. This causes the secondary sound source to emit a control sound with the opposite phase to the original noise, thus interfering with and canceling out the original noise within the target area. Simultaneously, the controller updates the control filter weights online based on the latest acquired error signal, enabling the control parameters to adaptively adjust according to changes in noise characteristics, thereby continuously maintaining the noise reduction effect.

[0164] Furthermore, during the cyclical operation of the control algorithm, the system also incorporates a divergence detection mechanism. This divergence detection is used to determine whether the current controller output and error signal changes exceed a preset stable range. When no divergence is detected, the system continues the cyclical process of reference signal acquisition, error signal acquisition, noise suppression signal output, and filter weight update. When algorithm divergence or control anomalies are detected, the system returns to the control initialization phase, reloading the secondary path, acoustic feedback path, and control filter parameters to restore stable system operation. Through these methods, the active noise control system can maintain good real-time performance, stability, and robustness under complex operating conditions.

[0165] In this embodiment, the initialization configuration section mainly ensures that the audio link and control parameters can be correctly established, while the control algorithm section mainly completes noise reference acquisition, residual error detection, adaptive control output, and parameter iterative update. The two work together to form a complete active noise control operation method. This method is applicable to active noise control of composite noise under air-cooled heat dissipation systems and open sound field conditions, and is especially suitable for embedded active noise cancellation scenarios that require long-term continuous operation and have high requirements for real-time performance and stability.

[0166] Figure 5 This is a flowchart of the active-passive fusion noise reduction method provided in an embodiment of the present invention, as follows: Figure 5 As shown, the initial composite noise is generated by a wind-cooled noise source. This initial composite noise contains both low-frequency broadband noise floor and discrete narrowband peaks. The noise propagates along its path and first enters a passive noise reduction section. This passive noise reduction section employs a micro-perforated coupled coiled cavity sound-absorbing structure to pre-absorb the target low-frequency noise components, thereby reducing the low-frequency sound energy in the initial noise and lessening the burden on subsequent active control. After passive noise reduction, a residual composite noise signal is formed and is sent to the reference signal acquisition terminal and the subsequent active noise control section, respectively.

[0167] The active noise reduction section includes a controller comprising a broadband control branch and a narrowband control branch. The broadband control branch suppresses continuous broadband noise floor, preferably using a variable step-size normalized FxLMS algorithm with acoustic feedback cancellation. The narrowband control branch suppresses discrete narrowband peaks, preferably using a frequency self-tracking notch filter FxLMS algorithm. The two branches perform calculations based on the reference signal and error signal respectively to obtain corresponding broadband and narrowband control outputs, which are then fused within the controller to form an active control signal. This active control signal drives a secondary sound source to emit a control sound with a phase opposite to the residual composite noise, causing the control sound and residual noise to interfere and cancel each other out in the target area. Simultaneously, an error sensor collects the residual noise after cancellation and feeds the error signal back to the controller to achieve online updates of the parameters of the two control branches.

[0168] The active-passive fusion noise reduction method for air-cooled low-frequency noise provided in this embodiment of the invention can be implemented by an active-passive fusion noise reduction system for air-cooled low-frequency noise. This embodiment of the invention uses the active-passive fusion noise reduction system for air-cooled low-frequency noise executing the active-passive fusion noise reduction method for air-cooled low-frequency noise as an example to illustrate the active-passive fusion noise reduction system for air-cooled low-frequency noise provided in this embodiment of the invention.

[0169] This invention also provides an active-passive fusion noise reduction system for low-frequency noise from air-cooled systems, such as... Figure 3 As shown, the active and passive fusion noise reduction system for low-frequency noise from air-cooled systems includes: an acquisition module 610, a first processing module 620, a second processing module 630, and a third processing module 640.

[0170] The acquisition module 610 is used to acquire air-cooled low-frequency noise, transmit the air-cooled low-frequency noise into a passive sound-absorbing component, and preprocess the air-cooled low-frequency noise through a micro-perforated coupled coiled cavity sound-absorbing structure to obtain composite noise. The micro-perforated coupled coiled cavity sound-absorbing structure includes a micro-perforated plate, a coiled cavity, and a base plate. The micro-perforated plate has multiple micro-holes. The air-cooled low-frequency noise enters the coiled cavity after passing through the micro-holes. The composite noise includes broadband noise and narrowband noise. The first processing module 620 is used to transmit the composite noise to the active noise control component and acquire the reference signal of the composite noise and the residual noise error signal in the target area through the reference sensor and the error sensor. The second processing module 630 is used to transmit the reference signal and the residual noise error signal to the controller, and control the broadband control branch and the narrowband control branch to perform calculations on the reference signal to obtain the total control signal. The controller is used to control the broadband control branch and the narrowband control branch. The residual noise error signal is used to update the parameters of the broadband control branch and the narrowband control branch. The broadband control branch is used to suppress continuous broadband background noise, and the narrowband control branch is used to suppress discrete narrowband peak noise. The third processing module 640 is used to transmit the main control signal to the secondary sound source, so that the secondary sound source generates control sound that cancels out the low-frequency noise of the air-cooled system, thereby achieving synergistic suppression of the low-frequency noise of the air-cooled system. The active noise control component includes a reference sensor, an error sensor, a controller, and a secondary sound source.

[0171] The active-passive fusion noise reduction system for low-frequency air-cooled noise provided in this embodiment of the invention can achieve... Figures 1 to 5 The various processes implemented in the embodiment of the active and passive fusion noise reduction method for low-frequency noise in air-cooled systems will not be described in detail here to avoid repetition.

[0172] In some embodiments, such as Figure 7As shown, this embodiment of the invention also provides an electronic device 700, including a processor 701, a memory 702, and a computer program stored in the memory 702 and executable on the processor 701. When the program is executed by the processor 701, it implements the various processes of the above-described active and passive fusion noise reduction method embodiment for air-cooled low-frequency noise and achieves the same technical effect. To avoid repetition, it will not be described again here.

[0173] It should be noted that the electronic devices in the embodiments of the present invention include the mobile electronic devices and non-mobile electronic devices described above.

[0174] This invention also provides a non-transitory computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the various processes of the above-described active-passive fusion noise reduction method for air-cooled low-frequency noise and achieves the same technical effect. To avoid repetition, it will not be described again here.

[0175] The processor is the processor in the electronic device described in the above embodiments. The readable storage medium includes computer-readable storage media, such as computer read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk.

[0176] This invention also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described active-passive fusion noise reduction method for low-frequency noise from air-cooled systems.

[0177] The processor is the processor in the electronic device described in the above embodiments. The readable storage medium includes computer-readable storage media, such as computer read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk.

[0178] This invention also provides a chip, which includes a processor and a communication interface. The communication interface and the processor are coupled. The processor is used to run programs or instructions to implement the various processes of the above-described active and passive fusion noise reduction method for air-cooled low-frequency noise, and can achieve the same technical effect. To avoid repetition, it will not be described again here.

[0179] It should be understood that the chip mentioned in the embodiments of the present invention may also be referred to as a system-on-a-chip, system chip, chip system, or system-on-a-chip, etc.

[0180] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element. Furthermore, it should be noted that the scope of the methods and systems in the embodiments of the present invention is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0181] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a computer software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal (which may be a mobile phone, computer, server, or network device, etc.) to execute the active and passive fusion noise reduction method for wind-cooled low-frequency noise of the various embodiments of the present invention.

[0182] In the description of this invention, "first feature" and "second feature" may include one or more of the features.

[0183] In the description of this invention, "a plurality of" means two or more.

[0184] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

[0185] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0186] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for active and passive fusion noise reduction of low-frequency noise from air-cooled systems, characterized in that, The method includes: Low-frequency air-cooled noise is acquired and emitted into a passive sound-absorbing component. The low-frequency air-cooled noise is pre-processed through a micro-perforated coupled coiled cavity sound-absorbing structure to obtain composite noise. The micro-perforated coupled coiled cavity sound-absorbing structure includes a micro-perforated plate, a coiled cavity, and a base plate. Multiple micro-holes are formed on the micro-perforated plate. The low-frequency air-cooled noise passes through the micro-holes and enters the coiled cavity. The composite noise includes broadband noise and narrowband noise. The composite noise is transmitted to the active noise control component, and the reference signal of the composite noise and the residual noise error signal in the target area are acquired by the reference sensor and the error sensor. The reference signal and residual noise error signal are transmitted to the controller, which controls the broadband control branch and the narrowband control branch to perform calculations on the reference signal to obtain the total control signal. The controller is used to control the broadband control branch and the narrowband control branch. The residual noise error signal is used to update the parameters of the broadband control branch and the narrowband control branch. The broadband control branch is used to suppress continuous broadband background noise, and the narrowband control branch is used to suppress discrete narrowband peak noise. The main control signal is transmitted to the secondary sound source, which generates a control sound that cancels out the low-frequency noise of the air-cooled system, thus achieving synergistic suppression of the low-frequency noise of the air-cooled system. The active noise control component includes a reference sensor, an error sensor, a controller, and a secondary sound source.

2. The active-passive fusion noise reduction method for low-frequency noise from air-cooled systems according to claim 1, characterized in that, The process involves emitting low-frequency air-cooled noise into a passive sound-absorbing component, and pre-processing the low-frequency air-cooled noise through a micro-perforated coupled coiled cavity sound-absorbing structure to obtain composite noise, including: The air-cooled low-frequency noise is emitted onto the micro-perforated plate, allowing the air-cooled low-frequency noise to enter the coiled cavity through the micro-perforations on the micro-perforated plate. The sound-absorbing structure formed by coupling the micro-perforated plate with the coiled cavity absorbs the low-frequency noise of air cooling, resulting in composite noise; The micro-perforated coupled coiled cavity sound-absorbing structure is constructed based on an electro-acoustic analogy method to build an equivalent impedance model. The air column in the micro-perforation is equivalent to acoustic mass, the thermal viscous loss of the micro-perforation wall and the inner wall of the coiled cavity is equivalent to acoustic resistance, and the closed back cavity is equivalent to acoustic capacitance. The total impedance of the micro-perforated coupled coiled cavity sound-absorbing structure meets the impedance matching requirements near the target frequency. The real part of the total impedance is close to the characteristic impedance of air, and the imaginary part is close to zero.

3. The active-passive fusion noise reduction method for low-frequency noise from air-cooled systems according to claim 1, characterized in that, The passive sound-absorbing component is disposed on the sound propagation path of the air outlet, the active noise control component is disposed in the open sound field of the air outlet, and the controller adopts a feedforward, multi-channel, wide and narrow band fusion control structure, which prioritizes noise control for the open sound field of a single air outlet.

4. The active-passive fusion noise reduction method for low-frequency noise from air-cooled systems according to claim 1, characterized in that, The process of transmitting the reference signal and residual noise error signal to the controller, and controlling the broadband control branch and the narrowband control branch to perform calculations on the reference signal to obtain the total control signal includes: The reference signal and residual noise error signal are transmitted to the controller. The narrowband control branch uses the frequency self-tracking notch filter FxLMS algorithm to calculate the reference signal, track the discrete narrowband peak components in the reference signal, and obtain the narrowband control output and the dominant frequency estimation result. The reference signal and the dominant frequency estimation results are used as inputs to the broadband control branch. The variable step size normalized FxLMS algorithm with acoustic feedback cancellation is used to calculate the reference signal and the dominant frequency estimation results to obtain the broadband control output. The narrowband control output and the wideband control output are superimposed and fused in the time domain to obtain the total control signal.

5. The active-passive fusion noise reduction method for low-frequency noise from air-cooled systems according to claim 4, characterized in that, The FxLMS algorithm, which employs frequency self-tracking notch filtering, is used to process the reference signal, tracking the discrete narrowband peak components within the reference signal to obtain the narrowband control output and dominant frequency estimation results, including: Obtain the short-time spectrum of the reference signal and construct a narrow-band search interval; Instantaneous main frequency estimation is performed within the search interval to obtain the instantaneous main frequency estimation result; The instantaneous dominant frequency estimation results are smoothed, and harmonic components are constructed. The orthogonal reference signal of the narrowband control branch is constructed based on the instantaneous main frequency estimation result and the harmonic components; The orthogonal narrowband reference signal is transmitted to the narrowband control filter for filtering to obtain the narrowband control output and the dominant frequency estimation result. The weight update of the narrowband control filter includes: The orthogonal reference signal of the narrowband control branch is transmitted to the secondary path estimation model for pre-filtering to obtain the narrowband filter reference vector; Using a fixed step size, the weights of the narrowband control filter are iteratively updated based on the residual noise error signal and the narrowband filter reference vector.

6. The active-passive fusion noise reduction method for low-frequency noise from air-cooled systems according to claim 4, characterized in that, The variable step-size normalized FxLMS algorithm with acoustic feedback cancellation is used to calculate the reference signal and the dominant frequency estimation results to obtain a broadband control output, including: The net reference signal is obtained by subtracting the feedback component from the reference signal, wherein the feedback component is estimated based on the acoustic feedback path model; Based on the dominant frequency estimation results, the corresponding spectral line components in the net reference signal are suppressed to obtain the broadband branch-specific reference signal; The broadband branch-specific reference signal is transmitted to the broadband control filter for filtering to obtain the broadband control output.

7. The active-passive fusion noise reduction method for low-frequency noise from air-cooled systems according to claim 6, characterized in that, The method further includes: The broadband tributary-specific reference signal is transmitted to the secondary path estimation model for pre-filtering to obtain the broadband filtered reference vector; The step size is normalized based on the instantaneous energy of the broadband filter reference vector to obtain the normalized step size. The power of the residual noise error signal is smoothed and estimated to obtain the error power estimation result; The step size is adaptively adjusted based on the error power estimation results to obtain a variable step size. The weights of the broadband controlled filter are iteratively updated based on the variable step size, residual noise error signal, and broadband filter reference vector.

8. A combined active and passive noise reduction system for low-frequency air-cooled systems, implemented using the combined active and passive noise reduction method for low-frequency air-cooled systems as described in any one of claims 1 to 7, characterized in that... The system includes: The acquisition module is used to acquire air-cooled low-frequency noise, transmit the air-cooled low-frequency noise into the passive sound-absorbing component, and preprocess the air-cooled low-frequency noise through a micro-perforated coupled coiled cavity sound-absorbing structure to obtain composite noise. The micro-perforated coupled coiled cavity sound-absorbing structure includes a micro-perforated plate, a coiled cavity and a base plate. The micro-perforated plate has multiple micro-holes. The air-cooled low-frequency noise enters the coiled cavity after passing through the micro-holes. The composite noise includes broadband noise and narrowband noise. The first processing module is used to transmit the composite noise to the active noise control component and acquire the reference signal of the composite noise and the residual noise error signal in the target area through the reference sensor and the error sensor. The second processing module is used to transmit the reference signal and the residual noise error signal to the controller, and control the broadband control branch and the narrowband control branch to perform calculations on the reference signal to obtain the total control signal. The controller is used to control the broadband control branch and the narrowband control branch. The residual noise error signal is used to update the parameters of the broadband control branch and the narrowband control branch. The broadband control branch is used to suppress continuous broadband background noise, and the narrowband control branch is used to suppress discrete narrowband peak noise. The third processing module is used to transmit the main control signal to the secondary sound source, so that the secondary sound source generates control sound that cancels out the low-frequency noise of the air-cooled system, thereby achieving synergistic suppression of the low-frequency noise of the air-cooled system. The active noise control component includes a reference sensor, an error sensor, a controller, and a secondary sound source.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the active-passive fusion noise reduction method for air-cooled low-frequency noise as described in any one of claims 1 to 7.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the active-passive fusion noise reduction method for air-cooled low-frequency noise as described in any one of claims 1 to 7.

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