Design method for active and passive switching sound absorption control system of dielectric loudspeaker

Abstract

The invention belongs to the technical field of sound absorption and noise reduction, and relates to a design method of a sound absorption control system for active and passive switching of a dielectric loudspeaker, which comprises the following steps of: (1) designing a dielectric loudspeaker structure; (2) designing a noise acquisition system; (3) designing an active and passive switching sound absorption control system; (4) designing an active noise reduction control system; and (5) measuring and designing the sound absorption coefficient of the sound absorption structure of the dielectric loudspeaker. According to the invention, active noise reduction control or passive noise reduction control can be selected for noise with different frequencies, so that a good sound absorption effect is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sound absorption and noise reduction, and relates to a design method for an active and passive switching sound absorption control system of a dielectric loudspeaker. Background Art

[0002] With the continuous research of various researchers in the field of acoustics, various loudspeakers and various research results on noise control have emerged one after another. For example, there are piezoelectric loudspeakers and thin-film loudspeakers, etc. The research results of noise control include micro-perforated structures, active noise control, thin-film acoustic metamaterials, structural acoustic metamaterials, etc. These research results have achieved good results in their respective fields. However, with the extensive research on thin films in the field of acoustics, thin-film acoustic metamaterials and loudspeaker structures designed based on dielectric elastomer films have emerged one after another.

[0003] In recent years, the research on thin-film sound absorbers has focused on the following aspects: First, a mass block is attached to the thin film, and by changing the shape, quantity, and type of the attached mass, as well as changing the position of the attached mass on the thin film and the opening at the back cavity of the hybrid film resonator, a thin-film sound absorption structure is constructed; second, the thin film is combined with materials such as micro-perforated plates to form a sound absorption structure. In addition, new thin-film materials are designed to construct a sound absorber structure. However, existing passive noise reduction structures such as thin-film sound absorbers or film-type metamaterials have deficiencies. For example, after the structural parameters are determined, the sound absorption and noise reduction frequency band is relatively fixed, which limits its noise reduction frequency range and has certain limitations in actual application. In addition, for the thin-film metamaterial structure with an attached mass, the attached mass block not only increases the weight of the structure, but also increases the preparation difficulty of the thin-film metamaterial structure to ensure good adhesion between the mass block and the thin film.

[0004] Dielectric elastomer materials are a new type of electroactive material with unique properties such as large elongation, high specific elastic energy density, and good response speed. At present, most of the applications of dielectric elastomers in the field of acoustic noise reduction are to use their deformation generated by electrification to make adjustable acoustic resonators. Secondly, many scholars have also designed various loudspeaker models using the properties of dielectric elastomer films. Few scholars have combined the two to use dielectric elastomer materials to make a thin-film structure that can be used for both active noise control and passive noise control. Therefore, the present invention provides a new design idea for the application of thin-film acoustic structures in the field of noise reduction. At the same time, the present invention can adopt different sound absorption and noise reduction methods for different noises, greatly enhancing the reliability of noise reduction. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the present invention aims to provide a design method for an absorption control system with active and passive switching of a dielectric loudspeaker. Based on the fact that the dielectric loudspeaker can be used as a secondary sound source in active noise control to generate an anti-phase sound wave to cancel out the target noise and achieve sound absorption and noise reduction, and the dielectric loudspeaker can be used as a thin-film sound absorption structure to achieve sound absorption and noise reduction based on the principle of resonance sound absorption. Since the dielectric loudspeaker has two different ways of sound absorption and noise reduction, active noise control or passive noise control can be selected to achieve a better sound absorption and noise reduction effect on the target noise.

[0006] Since the dielectric elastomer material, as a new type of electroactive material, has unique properties such as large elongation, high specific elastic energy density, and good response speed. The present invention uses a dielectric elastomer film to design an acoustic structure with both active and passive sound absorption functions, called a dielectric loudspeaker, which can be used for passive noise control and can also be used as an active sound absorption and noise reduction unit to achieve the function of sound absorption and noise reduction. Based on this, a design method for an absorption control system with active and passive switching of a dielectric loudspeaker is proposed. When the target noise is input, the data signal processor (DSP) will analyze the noise signal and select to generate an acoustic wave signal with a phase opposite to that of the noise (anti-phase sound wave), and transmit this anti-phase sound wave signal to the high-voltage amplifier. The high-voltage amplifier connects the dielectric loudspeaker to make the dielectric loudspeaker emit the anti-phase sound wave to cancel out the target noise, thereby achieving active sound absorption and noise reduction; or the data signal processor (DSP) chooses not to generate an acoustic wave signal, and relies on the passive sound absorption effect of the dielectric loudspeaker to achieve sound absorption and noise reduction of the target noise.

[0007] The present invention is realized through the following technical solutions.

[0008] A design method for an absorption control system with active and passive switching of a dielectric loudspeaker, the steps are as follows:

[0009] (1) Design of the dielectric loudspeaker structure

[0010] The dielectric speaker structure described in the design of the active and passive switching sound absorption control system of the dielectric speaker is a single cylindrical structure, which includes a circular dielectric elastomer film, a rectangular dielectric elastomer film coated with a flexible electrode, a film plate composed of two hollowed-out annular thin plates fixing the dielectric elastomer film, a circular bottom plate, screws, nuts, and an outer wall. The selected dielectric elastomer film is thermoplastic polyurethane elastomer (TPU), and the selected flexible electrode is conductive silver paste. The outer wall is a hollow cylinder. The annular thin plate, the circular bottom plate and the outer wall are all made by 3D printing. One end of the film coated with the flexible electrode is adhered to the center of the film plate, and the other end is adhered to the base. The thin plate and the base are fixed with screws or brackets and separated by a certain distance to form a structure with a cross-section similar to "工". Conductive tape is attached to both sides of the rectangular dielectric elastomer film coated with the flexible electrode, and it is connected to the high-voltage amplifier with a wire. A back cavity is formed between the film plate, the circular bottom plate and the outer wall; through data The signal processor (DSP) analyzes and processes the collected noise signal, and chooses whether to generate a sound wave signal (anti-phase sound wave) with a phase opposite to that of the noise, and transmits the anti-phase sound wave signal to the high-voltage amplifier. The high-voltage amplifier amplifies the voltage of the anti-phase sound wave signal and applies an alternating electric field to drive the rectangular dielectric elastomer film coated with the flexible electrode to drive the film on the film plate to vibrate and make sound, thereby generating an anti-phase sound wave that is emitted and offsets the target noise, thereby realizing active noise reduction control or absorbing the target noise by relying on the passive sound absorption and noise reduction performance of the dielectric speaker, thereby forming a dielectric speaker structure with switchable active and passive noise reduction control;

[0011] (2) Design of noise collection system

[0012] When the noise signal is input, the signal will be transmitted through the sound transmission pipe. In order to accurately collect the noise signal, a high-precision sound pressure acquisition card and a sound pressure sensor are used. The sound pressure sensor is connected to the sound pressure acquisition card, and the appropriate sampling rate and sampling time are set during the acquisition process. The collected noise signal is preprocessed, such as removing the DC bias or using a bandpass filter to remove high-frequency noise or low-frequency interference. The preprocessed noise signal is processed and analyzed by the graphical programming software Labview. The spectrum measurement tool in the Labview software is used to perform a fast Fourier transform (FFT) on the preprocessed noise signal, converting the time domain signal into a frequency domain signal. The frequency corresponding to the maximum amplitude in the frequency domain signal is extracted as the characteristic frequency of the noise. The frequency domain signal is further analyzed to obtain the frequency distribution of the noise signal. Then the sound pressure acquisition card is inserted into the subsequent controller, and the collected noise characteristic frequency is passed to the control program for subsequent processing and control.

[0013] (3) Design of active and passive switching sound absorption control system

[0014] The controller receives the data transmitted by the noise acquisition system, and through the control equation, selects one of the active noise reduction control or passive noise reduction control, which is an acoustic absorption control method, to enable the dielectric speaker structure to achieve the optimal acoustic absorption effect on the target noise. The core of the control equation is to select the better one from the different acoustic absorption effects of the two acoustic absorption control methods of the dielectric speaker structure on the target noise. Therefore, it is necessary to obtain the acoustic absorption coefficient of the passive noise reduction control and the acoustic absorption coefficient of the active noise reduction control of the dielectric speaker structure for a certain target noise frequency through experiments in advance, and then establish a functional relationship to form a control equation program. When facing a certain known noise frequency, the control equation program issues an instruction through comparison, and selectively allows the digital signal processor (DSP) to generate an acoustic wave signal (anti-acoustic wave) with a phase opposite to that of the target noise frequency, and then transmits this anti-acoustic wave signal to the high-voltage amplifier. The high-voltage amplifier connects to the dielectric speaker to make the dielectric speaker emit the anti-acoustic wave to cancel the target noise; or the digital signal processor (DSP) does not generate a signal, resulting in the dielectric speaker not vibrating and sounding, and relying on its own acoustic absorption structure to reduce noise.

[0015] (4) Design of the active noise reduction control system;

[0016] An active noise reduction control system with a dielectric speaker as the control source is established, mainly including a controller, a sound pressure sensor, and a dielectric speaker, etc. The controller is implemented on a digital platform (such as an STM development board or DSP, etc.), and the FeLMS algorithm is selected and studied in depth. According to actual requirements, the FeLMS algorithm is specifically improved and optimized to effectively reduce the computational amount of the control system and accelerate its convergence speed. With the acoustic absorption coefficient as the optimization target, a suitable reference strategy is deeply explored, aiming to improve its coherence with the error signal, and comprehensively analyze the core factors affecting the causality of the system. In order to verify the performance of the active noise control system, a comprehensive performance analysis and experimental verification are carried out for the system with a dielectric speaker as the control source. Through these studies, the frequency upper limit and effective acoustic absorption bandwidth of the active control system are clarified. In practical applications, when the primary noise sound wave has not yet reached the dielectric speaker structure, the controller can accurately control the vibration of the dielectric elastomer film. This accurate control can effectively adjust the amplitude and phase of the sound wave, and then significantly optimize the acoustic absorption performance of the array structure to achieve excellent acoustic absorption effects.

[0017] (5) Design of the measurement of the acoustic absorption coefficient of the acoustic absorption structure of the dielectric speaker

[0018] The measurement of the acoustic absorption coefficient of the acoustic absorption structure of the dielectric speaker is measured by the exchange channel method in an impedance tube, compared with the noise frequency, and the data is fed back to the control system. The digital signal processor (DSP) dynamically adjusts the amplitude and phase of the generated anti-acoustic wave or does not generate an anti-acoustic wave signal according to the fed-back signal.

[0019] This method is summarized as follows: First, a computer emits a noise signal, which is measured by a noise acquisition system and input into a digital signal processor (DSP). The DSP analyzes the noise signal, generates an acoustic wave signal (anti-phase acoustic wave) with a phase opposite to that of the noise according to the noise signal frequency, and transmits this anti-phase acoustic wave signal to a high-voltage amplifier. The high-voltage amplifier connects to a dielectric loudspeaker to make the dielectric loudspeaker emit the anti-phase acoustic wave to cancel out the target noise, thereby achieving active sound absorption and noise reduction; or choose not to generate an acoustic wave signal and rely on the passive sound absorption effect of the dielectric loudspeaker to achieve sound absorption and noise reduction of the target noise.

[0020] Furthermore, the designed sound absorption control system with active and passive switching of the dielectric loudspeaker includes a computer, an impedance tube, a loudspeaker, a sound pressure sensor, a sound pressure acquisition card, a power amplifier, a noise and vibration signal analyzer, a dielectric loudspeaker, a high-voltage amplifier, and a digital signal processor. The computer is externally connected to the noise and vibration signal analyzer and the digital signal processor. One end of the noise and vibration signal analyzer receives the noise signal given by the computer, and the other end is connected to the power amplifier. The power amplifier is externally connected to the loudspeaker to facilitate the noise signal output by the computer to make the loudspeaker emit noise through power amplification; the sound pressure sensor collects the noise signal and inputs it into the digital signal processor through the sound pressure acquisition card and the computer. The digital signal processor is connected to the high-voltage amplifier, and the high-voltage amplifier is connected to the dielectric loudspeaker. The loudspeaker and the dielectric loudspeaker are respectively arranged at both ends of the impedance tube. The digital signal processor selectively generates or does not generate an anti-phase acoustic wave signal with a phase opposite to that of the target noise frequency, so that the dielectric loudspeaker emits an anti-phase acoustic wave to cancel out the target noise or relies on its own structure for sound absorption and noise reduction.

[0021] In the present invention, the characteristic frequency of the noise signal is measured by the noise acquisition system and input into the sound absorption control system with active and passive switching. According to the measured noise characteristic frequency, the advantages and disadvantages of active noise reduction control and passive noise reduction control at this noise characteristic frequency are compared. According to the comparison result, if the active noise reduction control is better, the collected noise signal will be transmitted to a digital signal processor (DSP) or a similar processing unit such as an STM development board. The DSP will analyze the noise signal and generate an acoustic wave signal (anti-phase acoustic wave) with a phase opposite to that of the noise, and then transmit this anti-phase acoustic wave signal to the high-voltage amplifier. The high-voltage amplifier connects to the dielectric loudspeaker to make the dielectric loudspeaker emit the anti-phase acoustic wave to cancel out the target noise, thereby achieving sound absorption and noise reduction. On the contrary, if the passive noise reduction control is better, the DSP does not generate an acoustic wave signal to make the dielectric loudspeaker emit sound, and relies on the passive sound absorption and noise reduction performance of the dielectric loudspeaker to achieve the absorption of the target noise.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] 1. The design method of the active and passive switching sound absorption control system described in the invention for the dielectric loudspeaker can select active noise reduction control or passive noise reduction control for noises of different frequencies, so as to achieve a good sound absorption effect.

[0024] 2. Compared with the thin-film sound absorption structure, the dielectric loudspeaker of the present invention will not have a relatively fixed sound absorption and noise reduction frequency band after the structural parameters are determined. By adopting two different noise reduction methods, a higher sound absorption coefficient and a wider sound absorption frequency band can be achieved.

[0025] 3. Compared with the traditional active noise reduction control technology, selecting the dielectric loudspeaker as the secondary sound source can reduce the weight of the active noise reduction control system.

[0026] 4. The design method of the dielectric loudspeaker structure of the active and passive switching sound absorption control system is simple, providing a new design idea for the application of the thin-film acoustic structure in the field of noise reduction. Description of the Drawings

[0027] Figure 1 is a three-dimensional schematic diagram of the dielectric loudspeaker structure in the present invention;

[0028] Figure 2 is an overall structural schematic diagram of the design method of the active and passive switching sound absorption control system of the present invention;

[0029] Figure 3 is a flowchart of the design method of the active and passive switching sound absorption control system of the present invention;

[0030] Figure 4 is a comparison diagram of the theoretical calculation and experimental results of the passive noise control of the dielectric loudspeaker structure in the present invention;

[0031] Figure 5 is the frequency response curve and coherence diagram of the dielectric loudspeaker structure in the present invention

[0032] Figure 6 is a comparison diagram of the active noise reduction control variable phase and passive noise reduction control of the dielectric loudspeaker for the 600 Hz noise frequency in the present invention;

[0033] In the figure: 1. Dielectric elastomer film, 2. Flexible electrode, 3. Annular thin plate, 4. Outer wall surface, 5. Screw, 6. Circular bottom plate, 7. Loudspeaker, 8. Impedance tube, 9. Dielectric loudspeaker, 10. Sound pressure sensor, 11. Sound pressure acquisition card, 12. Computer, 13. Vibration signal analyzer, 14. Power amplifier, 15. Data signal processor, 16. High-voltage amplifier. Detailed Embodiments

[0034] The present invention will be further described below in conjunction with the drawings and specific embodiments, but it is not limited to the present invention.

[0035] A design method for a dielectric loudspeaker active-passive switching sound absorption control system, the steps of which are as follows:

[0036] (1) Design of dielectric speaker structure

[0037] The dielectric speaker structure described in the design of the active and passive switching sound absorption control system of the dielectric speaker is a single cylindrical structure, which includes a circular dielectric elastomer film, a rectangular dielectric elastomer film coated with a flexible electrode, a film plate composed of two hollowed-out annular thin plates fixing the dielectric elastomer film, a circular bottom plate, screws, nuts, and an outer wall. The selected dielectric elastomer film is thermoplastic polyurethane elastomer (TPU), and the selected flexible electrode is conductive silver paste. The outer wall is a hollow cylinder. The annular thin plate, the circular bottom plate and the outer wall are all made by 3D printing. One end of the film coated with the flexible electrode is adhered to the center of the film plate, and the other end is adhered to the base. The thin plate and the base are fixed with screws or brackets and separated by a certain distance to form a structure with a cross-section similar to "工". Conductive tape is attached to both sides of the rectangular dielectric elastomer film coated with the flexible electrode, and it is connected to the high-voltage amplifier with a wire. A back cavity is formed between the film plate, the circular bottom plate and the outer wall; through data The signal processor (DSP) analyzes and processes the collected noise signal, and chooses whether to generate a sound wave signal (anti-phase sound wave) with a phase opposite to that of the noise, and transmits the anti-phase sound wave signal to the high-voltage amplifier. The high-voltage amplifier amplifies the voltage of the anti-phase sound wave signal and applies an alternating electric field to drive the rectangular dielectric elastomer film coated with the flexible electrode to drive the film on the film plate to vibrate and make sound, thereby generating an anti-phase sound wave that is emitted and offsets the target noise, thereby realizing active noise reduction control or absorbing the target noise by relying on the passive sound absorption and noise reduction performance of the dielectric speaker, thereby forming a dielectric speaker structure with switchable active and passive noise reduction control;

[0038] (2) Design of noise collection system

[0039] After the noise signal is input, the signal will propagate through the sound transmission pipeline. To achieve accurate acquisition of the noise signal, a high-precision sound pressure acquisition card and a sound pressure sensor are used. The sound pressure sensor is connected to the sound pressure acquisition card, and during the acquisition process, appropriate sampling rates and sampling times are set. The acquired noise signal is preprocessed, such as removing the DC bias or using a band-pass filter to remove high-frequency noise or low-frequency interference. The preprocessed noise signal is processed and analyzed using the graphical programming software Labview. Using the spectrum measurement tool in the Labview software, a fast Fourier transform (FFT) is performed on the preprocessed noise signal to convert the time-domain signal into a frequency-domain signal. The frequency corresponding to the maximum amplitude is extracted as the characteristic frequency of the noise in the frequency-domain signal. The frequency-domain signal is further analyzed to obtain the frequency distribution of the noise signal. Then, the sound pressure acquisition card is inserted into the subsequent controller, and the acquired noise characteristic frequency is transmitted to the control program for subsequent processing and control;

[0040] (3) Design of the active and passive switching sound absorption control system

[0041] The controller receives the data transmitted by the noise acquisition system and selects one of the sound absorption control methods, active noise reduction control or passive noise reduction control, through the control equation to achieve the optimal sound absorption effect of the dielectric speaker structure on the target noise. The core of the control equation is to select the optimal one from the different sound absorption effects of the two sound absorption control methods of the dielectric speaker structure on the target noise. Therefore, it is necessary to obtain the sound absorption coefficient of the passive noise reduction control and the sound absorption coefficient of the active noise reduction control of the dielectric speaker structure for a certain target noise frequency through experiments in advance, and then establish a functional relationship to form a control equation program; when facing a certain known noise frequency, the control equation program issues an instruction through comparison, selectively enabling the digital signal processor (DSP) to generate a sound wave signal (anti-phase sound wave) with a phase opposite to the target noise frequency, and then transmitting this anti-phase sound wave signal to the high-voltage amplifier. The high-voltage amplifier connects to the dielectric speaker to make the dielectric speaker emit the anti-phase sound wave to cancel the target noise; or enabling the digital signal processor (DSP) not to generate a signal, resulting in the dielectric speaker not vibrating and sounding, and relying on its own sound absorption structure to reduce noise;

[0042] (4) Design of the active noise reduction control system;

[0043] An active noise reduction control system with a dielectric loudspeaker as the control source is established, mainly including a controller, a sound pressure sensor, a dielectric loudspeaker, etc. The controller is implemented on a digital platform (such as an STM development board or a DSP, etc.), and the FeLMS algorithm is selected and studied in depth. According to actual requirements, the FeLMS algorithm is specifically improved and optimized to effectively reduce the computational amount of the control system and accelerate its convergence speed. With the absorption coefficient as the optimization goal, a suitable reference strategy is explored in depth, aiming to improve its coherence with the error signal and comprehensively analyze the core factors affecting the causality of the system. To verify the performance of the active noise control system, a comprehensive performance analysis and experimental verification are carried out for the system with a dielectric loudspeaker as the control source. Through these studies, the frequency upper limit and effective absorption bandwidth of the active control system are clarified. In practical applications, when the primary noise wave has not yet reached the dielectric loudspeaker structure, the controller can accurately control the vibration of the dielectric elastomer film. This precise control can effectively adjust the amplitude and phase of the sound wave, thereby significantly optimizing the absorption performance of the array structure and achieving excellent absorption effects.

[0044] (5) Measurement design of the absorption coefficient of the dielectric loudspeaker absorption structure

[0045] The absorption coefficient of the dielectric loudspeaker absorption structure is measured by the exchange channel method in an impedance tube. Compared with the noise frequency, the data is fed back to the control system. The data signal processor (DSP) dynamically adjusts the amplitude and phase of the generated anti-sound wave or does not generate an anti-sound wave signal according to the fed-back signal.

[0046] The designed absorption control system with active and passive switching of the dielectric loudspeaker includes a computer 12, an impedance tube 8, a loudspeaker 7, a sound pressure sensor 10, a sound pressure acquisition card 11, a power amplifier 14, a noise and vibration signal analyzer 13, a dielectric loudspeaker 9, a high-voltage amplifier 16, and a data signal processor 15. The computer 12 is externally connected to the noise and vibration signal analyzer 13 and the data signal processor 15. One end of the noise and vibration signal analyzer 13 receives the noise signal given by the computer 12, and the other end is connected to the power amplifier 14. The power amplifier 14 is externally connected to the loudspeaker 7, facilitating the noise signal output by the computer to make the loudspeaker emit noise through power amplification; the sound pressure sensor 10 collects the noise signal and inputs it to the data signal processor 15 through the sound pressure acquisition card 11 and the computer 12. The data signal processor 15 is connected to the high-voltage amplifier 16, and the high-voltage amplifier 16 is connected to the dielectric loudspeaker 9. The loudspeaker 7 and the dielectric loudspeaker 9 are respectively arranged at both ends of the impedance tube 8. The data signal processor 15 selectively generates or does not generate an anti-sound wave signal with a phase opposite to the target noise frequency, so that the dielectric loudspeaker 9 emits an anti-sound wave to cancel the target noise or rely on its own structure for sound absorption and noise reduction.

[0047] Embodiment:

[0048] The front view schematic diagram of the overall structure adopted by the design method of the present invention is as Figure 2 shown. For the dielectric speaker structure, the annular thin plate, the circular bottom plate and the outer wall surface are all made by 3D printing, and their thicknesses are all 1 mm. The selected TPU film has a thickness of 0.1 mm, the rectangular film has a width of 20 mm and a length of 65 mm. The area where the flexible electrode is applied is rectangular, with a width of 18 mm and a length of 60 mm. The entire dielectric speaker structure is a cylindrical structure, the diameter of the cylinder is 10 cm, the distance from the circular film plate to the circular bottom plate is 7 cm, and M4*90 screws are selected.

[0049] 1. Through the verification of theoretical calculation and experiment, the passive sound absorption coefficient diagram of the dielectric speaker is obtained. The theoretical calculation results are calculated on Matlab. In the experiment, an AWA6290T type impedance tube measurement system is used, and the two-channel transfer function impedance method is adopted to measure the sound absorption coefficient of the dielectric speaker. The comparison diagram of the theoretical calculation and measurement results of the sound absorption coefficient of the dielectric speaker is as Figure 4 shown. The theoretical calculation results are in good agreement with the experimental results. The error exists because only the first-order mode of the dielectric speaker structure is calculated here. In addition, there are some errors in the measurement process of some parameters.

[0050] The dielectric speaker is placed in a self-made anechoic chamber to reduce the influence of environmental noise. A microphone is set above the dielectric speaker. The dielectric speaker is driven by a high-voltage amplifier and a signal generator. The high-voltage amplifier amplifies the sinusoidal alternating current signal swept by the signal generator and outputs an alternating current with an AC voltage amplitude of 600 V to the dielectric speaker. The signal is received and processed by a dynamic signal analyzer, and the measured frequency response spectrum of the speaker is obtained on the display as Figure 5 shown. Figure 5 The frequency response curve and coherence diagram of the dielectric speaker are displayed to verify that it can emit sound waves and can be used for active noise reduction control.

[0051] The above theoretical calculations and experiments provide a basis for the dielectric speaker to achieve passive noise reduction control and active noise reduction control.

[0052] 2. Before data acquisition, the sound pressure sensor needs to be calibrated to ensure its measurement accuracy. Then, the sound pressure sensor is connected to the sound pressure data acquisition card, and the acquisition card is inserted into the controller, and the controller is connected to the computer to realize the connection of data acquisition hardware and software.

[0053] 3. The extracted noise frequency signal is transmitted to a data signal processor (DSP). The control equation program controls whether the data signal processor (DSP) generates an acoustic wave signal (anti-acoustic wave) with a phase opposite to that of the target noise frequency according to the noise frequency signal, and then transmits this anti-acoustic wave signal to a high-voltage amplifier. The high-voltage amplifier connects to a dielectric loudspeaker to make the dielectric loudspeaker emit the anti-acoustic wave to cancel the target noise, or the dielectric loudspeaker does not receive a signal and does not vibrate actively to generate sound, and relies on its own sound absorption structure to reduce noise.

[0054] 4. After the dielectric loudspeaker emits the anti-acoustic wave to cancel the target noise, the sound absorption coefficient of the dielectric loudspeaker structure is measured in an impedance tube, and the data is fed back to the control system. The data signal processor (DSP) dynamically adjusts the amplitude and phase of the generated anti-acoustic wave according to the feedback signal, so as to achieve adaptive sound absorption of the target noise.

[0055] 5. For example, a sinusoidal wave signal with a noise frequency of 600 Hz is collected and transmitted to the data signal processor (DSP). According to the previously known sound absorption coefficient of the dielectric loudspeaker for a 600 Hz noise frequency, as Figure 6 shown, the control equation program controls whether the data signal processor (DSP) generates an acoustic wave signal (anti-acoustic wave) with a phase opposite to that of the target noise frequency, and then transmits this anti-acoustic wave signal to a high-voltage amplifier. The high-voltage amplifier connects to a dielectric loudspeaker to make the dielectric loudspeaker emit the anti-acoustic wave to cancel the target noise. After the dielectric loudspeaker emits the anti-acoustic wave to cancel the target noise, the sound absorption coefficient of the dielectric loudspeaker structure is measured in an impedance tube, and the data is fed back to the control system. The data signal processor (DSP) dynamically adjusts the amplitude and phase of the generated anti-acoustic wave according to the feedback signal, so as to achieve adaptive sound absorption of the target noise and make the sound absorption coefficient of the dielectric loudspeaker for the sinusoidal wave signal with a noise frequency of 600 Hz reach 0.98.

[0056] The above are only the preferred embodiments of the present invention, and do not limit the implementation manners and protection scope of the present invention. For those skilled in the art, it should be realized that all equivalent replacements and obvious changes made by using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A design method for a sound absorption control system for active and passive switching of a dielectric loudspeaker, characterized in that: The steps include: (1) Design of dielectric speaker structure The dielectric loudspeaker structure comprises a film plate, a circular bottom plate (6), and an outer wall surface (4). The film plate is composed of two hollowed-out annular thin plates (3) fixing a circular dielectric elastomer film (1). The film plate and the circular bottom plate (6) are fixed into a hollow cylindrical structure by screws (5) and nuts. A certain distance is separated between the film plate and the circular bottom plate (6). One end of the rectangular dielectric elastomer film (1) coated with a flexible electrode (2) is adhered to the center of the film plate, and the other end is adhered to the base. The film plate, the rectangular dielectric elastomer film (1), and the circular bottom plate (6) are combined into a structure with a cross section similar to that of an "I". The outer wall surface (4) is a hollow cylinder. The outer wall surface (4) wraps the "I" structure. Conductive tape is attached to both sides of the rectangular dielectric elastomer film (1) coated with the flexible electrode (2). It is connected to a high-voltage amplifier by a wire. A back cavity is formed between the film plate, the circular bottom plate (6), and the outer wall surface (4). (2) Design of noise collection system In order to achieve accurate acquisition of noise signals, a high-precision sound pressure acquisition card and a sound pressure sensor are used, the sound pressure sensor is connected to the sound pressure acquisition card, and during the acquisition process, a suitable sampling rate and sampling time are set; the acquired noise signal is preprocessed, and the preprocessed noise signal is processed and analyzed by the graphical programming software Labview, and the spectrum measurement tool in the Labview software is used to perform a fast Fourier transform on the preprocessed noise signal, and the time domain signal is converted into a frequency domain signal. The frequency corresponding to the maximum amplitude in the frequency domain signal is extracted as the characteristic frequency of the noise, and the frequency domain signal is further analyzed to obtain the frequency distribution of the noise signal, and then the sound pressure acquisition card is inserted into the subsequent controller, and the acquired noise characteristic frequency is passed to the control program for subsequent processing and control; (3) Design of active and passive switching sound absorption control system The controller receives the data transmitted by the noise collection system, and selects a sound absorption control method of active noise reduction control or passive noise reduction control through the control equation, so that the dielectric speaker structure can achieve the best sound absorption effect on the target noise. The core of the control equation is to select the best one for the two sound absorption control methods of the dielectric speaker structure with different sound absorption effects on the target noise. Therefore, it is necessary to obtain the passive noise reduction control sound absorption coefficient and the active noise reduction control sound absorption coefficient of the dielectric speaker structure for a certain target noise frequency through experiments in advance, and then establish a functional relationship to form a control equation program; when facing a known noise frequency, the control equation program issues an instruction through comparison, selectively allowing the data signal processor to generate an anti-phase sound wave signal with a phase opposite to the target noise frequency, and then transmits this anti-phase sound wave signal to the high-voltage amplifier, which is connected to the dielectric speaker by the high-voltage amplifier so that the dielectric speaker emits the anti-phase sound wave to offset the target noise; or the data signal processor does not generate a signal, resulting in the dielectric speaker not vibrating and making sound, and relying on its own sound absorption structure to reduce noise; (4) Design of active noise reduction control system Establish an active noise reduction control system with a dielectric speaker as the control source, including a controller, a sound pressure sensor and a dielectric speaker. The controller is implemented on a digital platform, and the FeLMS algorithm is selected and studied in depth. According to actual needs, the FeLMS algorithm is improved and optimized in a targeted manner to effectively reduce the amount of calculation of the control system and accelerate its convergence speed. Taking the sound absorption coefficient as the optimization target, we deeply explore the appropriate reference strategy to improve its coherence with the error signal and comprehensively analyze the core elements that affect the causality of the system. In order to verify the performance of the active noise control system, we conduct a comprehensive performance analysis and experimental verification with the dielectric speaker as the control source. Through these studies, the upper frequency limit and effective sound absorption bandwidth of active control systems are clarified; (5) Design of sound absorption coefficient measurement of dielectric speaker sound absorption structure The sound absorption coefficient of the dielectric speaker sound absorption structure is measured in an impedance tube by the exchange channel method, compared with the noise frequency, and the data is fed back to the control system. The data signal processor dynamically adjusts the amplitude and phase of the anti-phase sound wave or does not generate an anti-phase sound wave signal based on the feedback signal.

2. The method for designing a sound absorption control system for active and passive switching of a dielectric loudspeaker according to claim 1, characterized in that: The designed dielectric speaker active-passive switching sound absorption control system comprises a computer (12), an impedance tube (8), a speaker (7), a sound pressure sensor (10), a sound pressure acquisition card (11), a power amplifier (14), a noise vibration signal analyzer (13), a dielectric speaker (9), a high-voltage amplifier (16), and a data signal processor (15). The computer (12) is externally connected to the noise vibration signal analyzer (13) and the data signal processor (15). One end of the noise vibration signal analyzer (13) receives the noise signal given by the computer (12), and the other end is connected to the power amplifier (14). The power amplifier (14) is then externally connected to the speaker (7), which is convenient for the computer to input. The noise signal generated is amplified by power to make the loudspeaker emit noise; the sound pressure sensor (10) collects the noise signal and inputs it to the data signal processor (15) through the sound pressure acquisition card (11) and the computer (12); the data signal processor (15) is connected to the high-voltage amplifier (16); the high-voltage amplifier (16) is then connected to the dielectric loudspeaker (9); the loudspeaker (7) and the dielectric loudspeaker (9) are respectively arranged at two ends of the impedance tube (8); the data signal processor (15) selectively generates or does not generate an anti-phase sound wave signal with a phase opposite to the target noise frequency, so that the dielectric loudspeaker (9) emits an anti-phase sound wave to offset the target noise or relies on its own structure to absorb and reduce noise.

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