Combined excitation wide-range infrasound piston sound generating device

Abstract

The application discloses a combined excitation wide-range infrasound piston sound generating device, and belongs to the technical field of acoustic measurement. The device comprises a first piston excitation system, a laser vibration measuring instrument, a second piston excitation system and a rotating support. The laser vibration measuring instrument is installed on the rotating support and is arranged between the first piston excitation system and the second piston excitation system. The rotating support is configured to adjust the measurement direction of the laser vibration measuring instrument to align the first piston excitation system or the second piston excitation system for displacement measurement. The first piston excitation system and the second piston excitation system with different driving characteristics are configured, and an overlap area or a connecting area is arranged between adjacent range sections, so that the continuous coverage of a wide sound pressure range is realized, and the range expansion bottleneck caused by the limited driving capacity and motion precision of a single excitation mode, the nonlinear effect of a single piston cavity and a cylinder plug sealing structure under extreme working conditions is overcome.

Description

Technical Field

[0001] This invention relates to the field of acoustic metrology technology, specifically to a combined excitation type wide-range infrasound piston sound-generating device. Background Technology

[0002] A device that generates infrasound frequency sound pressure in a fixed and sealed air volume through the movement of one or more pistons with known volumetric velocity is called an infrasound piston generator. This generator is the core module for calibrating infrasound sensors using the laser piston method and the coupled cavity comparison method, and it can provide a highly stable, low-distortion standard infrasound wave for the calibration process.

[0003] Based on the strong penetrating power and long propagation distance of infrasound, the monitoring technology of infrasound source localization and identification using infrasound sensor arrays has been widely applied in fields such as national defense security, geological disaster prevention and control, and geophysical research. Infrasound sensors are the data source of infrasound monitoring systems. The accuracy of their sound pressure measurement and the quality of the target sound source radiation signal directly determine the accuracy of explosion yield estimation, target sound source localization, and feature identification, thus affecting the effectiveness and reliability of monitoring data and reconnaissance results. Furthermore, the dynamic range of the infrasound sensors determines the monitoring coverage of the system. Typically, near-field sensors require an upper limit of sound pressure dynamic range of no less than 10 kPa, while far-field sensors require a lower limit of sound pressure dynamic range of no more than 0.01 Pa. The constraint on the dynamic range is that the total harmonic distortion (THD) is no greater than 3%.

[0004] To meet the traceability requirements of the aforementioned wide dynamic range infrasound sensor, a wide-range infrasound piston generator needs to be developed. Its output sound pressure range should cover at least 0.01 Pa to 10 kPa, with a total harmonic distortion (THD) better than 3%. According to the electroacoustic analogy model of the piston generator, ideally, the radiated sound pressure within the piston generator is equal to the product of the volume velocity generated by the piston movement (proportional to the product of the piston area and piston displacement) and the acoustic transfer impedance of the piston cavity, i.e., directly related to the piston displacement and the structural parameters of the piston cavity. Currently, infrasound piston generators mostly employ a single piston cavity and cylinder-piston sealing structure or a single piston excitation method. The excitation source driving the piston movement includes a low-frequency vibration table, a moving-coil loudspeaker, or a linear motor. Limited by the driving capability and motion accuracy of the piston excitation source, as well as the nonlinear effect of the piston cavity, existing devices struggle to simultaneously achieve low-distortion, stable output at both extremely low sound pressure levels (e.g., 0.01 Pa) and extremely high sound pressure levels (e.g., 10 kPa). Specifically, to increase the upper limit of radiated sound pressure level, the piston motion needs to generate a large volume velocity and possess a high cavity acoustic transfer impedance, i.e., a large piston displacement and a small piston cavity volume. In this case, nonlinear effects such as air pressure compression, cavity leakage, or sealing membrane boundary constraints will introduce significant harmonic distortion, thus limiting the upper limit of radiated sound pressure level. Conversely, to extend the lower limit of radiated sound pressure level, the piston displacement needs to be small and the piston cavity volume large. Under small displacement conditions, the piston motion accuracy is difficult to guarantee and is easily affected by environmental vibrations, resulting in a low signal-to-noise ratio and insufficient stability. Therefore, wide-range sound pressure generation technology using a single piston cavity and cylinder seal structure or a single piston excitation method has significant performance bottlenecks. Summary of the Invention

[0005] In view of the limitations of existing technologies in terms of driving capability and motion accuracy due to the single excitation method, and the nonlinear effects of the single piston cavity and cylinder sealing structure under extreme conditions, which make it difficult to achieve the performance bottleneck of wide range and low harmonic distortion infrasound generation, the purpose of this invention is to provide a combined excitation wide range infrasound piston generation device.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The present invention provides a combined excitation type wide range infrasonic piston sound generating device, comprising: a first piston excitation system, a laser vibrometer, a second piston excitation system, and a rotating bracket. The laser vibrometer is mounted on the rotating bracket and placed between the first piston excitation system and the second piston excitation system. The rotating bracket is configured to adjust the measurement direction of the laser vibrometer to align with the first piston excitation system or the second piston excitation system for displacement measurement. The first piston excitation system includes a moving coil speaker, a first piston, a flexible diaphragm, a bottom cover, a sensor interface, and a top cover; the top cover is disposed on the bottom cover to form a first piston cavity, the moving coil speaker is disposed inside the bottom cover, the first piston is fixedly mounted on the moving coil speaker, the flexible diaphragm is pressed by a retaining ring with an edge concave-convex mating structure and fixed to the bottom cover by screws, and the sensor interface is disposed on the top cover. The second piston excitation system includes a linear motor, an adapter plate, a second piston, a guide structure, and a second piston cavity. The linear motor is fixedly connected to the second piston through the adapter plate. The second piston is coaxially fitted with the second piston cavity through the guide structure. The second piston and the guide structure are sealed using a non-contact gap sealing method.

[0007] In one implementation, the first piston excitation system generates low-distortion standard infrasound in the low sound pressure range of 0.01 Pa to 200 Pa, and the second piston excitation system generates low-distortion standard infrasound in the high sound pressure range of 100 Pa to 10 kPa.

[0008] In one implementation, the seal is a flexible film that provides a flexible contact seal when the first piston actuation system is in a small displacement condition.

[0009] In one embodiment, the first piston is installed above the mounting plane of the bottom cover, so that the flexible film is tightly stretched on the surface of the first piston.

[0010] In one embodiment, the second piston excitation system further includes a third piston chamber, a slide, and a base plate. The third piston chamber is mounted on the slide and is connected to or separated from the first piston chamber via the slide to adjust the overall volume of the piston chamber. The base plate is provided with an infrasound sensor interface, a temperature sensor interface, and a pressure sensor interface.

[0011] In one embodiment, low-distortion standard infrasound sensors are installed on the outside of the first piston cavity, the second piston cavity, and the third piston cavity to acquire the output sound pressure signal inside the piston cavity.

[0012] Based on the above technical solutions, the embodiments of the present invention can produce at least the following technical effects: (1) This invention achieves continuous coverage of a wide sound pressure range by configuring a first piston excitation system and a second piston excitation system with different driving characteristics and setting an overlap area or a connection area between adjacent range segments. This overcomes the limitations of driving capability and motion accuracy of a single excitation method and the bottleneck of range expansion caused by the nonlinear effect of a single piston cavity and cylinder seal structure under extreme conditions. At the same time, different sealing structures are adapted to the displacement characteristics of different excitation modules. In small displacement conditions, a flexible thin film contact seal is used to ensure high airtightness and anti-interference capability, avoiding the signal-to-noise ratio reduction and harmonic distortion caused by gap leakage. In large displacement conditions, a non-contact gap seal is used to avoid the nonlinear effect introduced by the flexible thin film contact seal during large displacement deformation. This solves the contradiction between high sound pressure range and low distortion from the mechanical structure level.

[0013] (2) This invention uses a low-distortion standard infrasound sensor to generate a harmonic compensation signal and correct the drive signal based on the actual sound pressure signal inside the cavity within the ultimate sound pressure range, thereby achieving active suppression of acoustic nonlinear distortion. Unlike traditional displacement feedback, which can only correct mechanical motion waveforms, this invention directly uses the final output sound pressure waveform as the feedback object, and can compensate in real time for harmonic distortion caused by a combination of factors such as finite amplitude propagation, cavity leakage, and mechanical properties of the sealing components, ensuring low distortion performance across the entire range, especially in the ultimate sound pressure range. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the overall structure of the combined excitation wide-range infrasonic piston sound-generating device according to an embodiment of the present invention. Figure 2 This is a cross-sectional view of a sound-generating device with a moving-coil loudspeaker as a piston excitation system according to an embodiment of the present invention. Figure 3 This is a cross-sectional view of a sound-generating device with a linear motor as the piston excitation system according to an embodiment of the present invention. Figure 4 This is a block diagram of the closed-loop control system of the infrasound piston sound-generating device according to an embodiment of the present invention.

[0016] In the figure, 1-first piston excitation system, 11-moving coil speaker, 12-first piston, 13-flexible film, 14-bottom cover, 15-first piston cavity, 16-sensor interface, 17-top cover, 18-clamping ring; 2-Laser Vibration Meter; 3-Second piston excitation system, 31-Linear motor, 32-Adapter plate, 33-Second piston, 34-Guide structure, 35-Second piston cavity, 36-Third piston cavity, 37-Slide table, 38-Base plate; 4-Rotating bracket. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0018] Example 1 like Figure 1 As shown, this invention proposes a combined excitation type wide-range infrasound piston sound generating device. Based on the driving capability characteristics of commonly used piston excitation systems, this device is configured with two sets of piston excitation systems, covering the sound pressure range of 0.01 Pa to 10 kPa in segments: In the low sound pressure range of 0.01 Pa to 200 Pa, a moving coil loudspeaker is used as the piston excitation system. This system has a small driving force, and the piston and cavity are sealed with a flexible membrane to improve airtightness and anti-interference ability, making it suitable for generating low-distortion, low-sound-pressure infrasound waves; In the high sound pressure range of 100 Pa to 10 kPa, a linear motor is used as the piston excitation system. This system has a large driving force and is more likely to obtain good motion accuracy over a large displacement range. An air gap seal is used between the piston and the cavity to avoid the nonlinear effects introduced by the sealing membrane under large displacement deformation conditions.

[0019] Specifically, the infrasound piston generating device includes a first piston excitation system 1, a laser vibrometer 2, a second piston excitation system 3, and a rotating bracket 4. The laser vibrometer 2 is mounted on the rotating bracket 4 and placed between the first piston excitation system 1 and the second piston excitation system 3. The rotating bracket 4 is configured to adjust the measurement direction of the laser vibrometer 2 so as to align with the first piston excitation system 1 or the second piston excitation system 3 for displacement measurement.

[0020] Specifically, the first piston excitation system 1 and the second piston excitation system 3 are configured to drive the piston to move within the piston cavity to generate infrasound waves, and these two sets of piston excitation systems cover different sound pressure ranges, with overlapping or connecting areas between adjacent sound pressure ranges. Figure 1 In the demonstrated example, the device base features two independent piston excitation systems: a moving-coil speaker piston excitation system on the right and a linear motor piston excitation system on the left. The moving-coil speaker is suitable for high-precision driving with small displacements, covering the low sound pressure range; while the linear motor is suitable for high-force driving with large strokes, covering the high sound pressure range. By setting overlapping or connecting areas between adjacent ranges, continuous and uninterrupted standard infrasound output can be ensured across the entire wide sound pressure range, avoiding calibration blind spots or data discontinuities caused by range switching.

[0021] like Figure 2 As shown, the design scheme using a moving-coil loudspeaker as the piston excitation system is implemented as follows: the first piston 12 is fixedly mounted on the moving-coil loudspeaker 11, and a flexible diaphragm 13 seals the first piston cavity 15 between it and the first piston cavity 15; the flexible diaphragm 13 is pressed by a pair of retaining rings 18 with an edge concave-convex mating structure, and the retaining rings 18 are fixed to the bottom cover 14 by screws; the first piston 12 is slightly higher than the mounting plane of the bottom cover 14 during installation, so that the flexible diaphragm 13 is tightly stretched on the surface of the first piston 12, ensuring good airtightness of the first piston cavity 15; an optical glass window of a certain diameter is provided on the upper surface of the top cover 17, which can be used for the incident beam of the laser vibrometer to achieve accurate measurement of the displacement of the first piston 12, and temperature and pressure sensor mounting interfaces are provided to support the absolute calibration of the infrasound sensor; in addition, two standard 1-inch sensor interfaces 16 are reserved on the top cover, and standard 1 / 2-inch sensors can also be compatible through adapters, and other adapter interfaces for infrasound sensors can be configured on the side wall as needed to support the implementation of the coupled cavity comparison method.

[0022] like Figure 3As shown, the design scheme using a linear motor as the piston excitation system is implemented as follows: the mover of the linear motor 31 is fixedly connected to the adapter plate 32, and the adapter plate 32 is then connected to the second piston 33; the second piston 33 is engaged with the second piston cavity 35 through the guide structure 34; the guide structure 34 and the second piston cavity 35 are connected and fixed to the fixed base of the linear motor 31 through an annular adapter, thereby ensuring that the second piston 33, the guide structure 34 and the second piston cavity 35 are coaxial; a gap seal is used between the second piston 33 and its guide structure 34 to avoid the nonlinear effects introduced by the flexible film under large displacement deformation conditions. In addition to the second piston cavity 35, this embodiment also includes a third piston cavity 36. Connecting the two cavities increases the total volume of the piston cavities, thereby reducing the output sound pressure under the same piston displacement conditions. The third piston cavity 36 is mounted on the slide table 37, facilitating convenient connection and separation between the cavities during sound pressure adjustment. When it is necessary to increase the cavity volume, the slide table 37 is used to push the third piston cavity 36 to mate with the second piston cavity 35 and lock it in place. When it is necessary to restore the small cavity, the locking mechanism is loosened and the cavity is slid away. The base plate 38 is equipped with interfaces for an infrasound sensor, a temperature sensor, and a pressure sensor, which can support absolute calibration and coupled cavity comparison calibration of the infrasound sensor.

[0023] Example 2 like Figure 4 As shown, to address the harmonic distortion problem in the high sound pressure range, this invention employs a sound pressure feedback closed-loop scheme for suppression. The specific implementation is as follows: a low-distortion standard infrasound sensor is installed on the outside of the piston cavity; the controller generates a single frequency... f The sinusoidal integer-cycle data sequence, after being converted from digital to analog (D / A), is used by a power amplifier to drive a piston excitation system, generating a frequency of... f The system generates sinusoidal infrasound waves. A standard infrasound sensor measures the infrasound signal output from the piston cavity. The response electrical signal is then processed through signal conditioning, A / D conversion, and spectrum analysis before being input to the feedback signal calculation module. Based on the spectrum analysis results, this module generates inverse compensation signals on the corresponding harmonic components. The digital compensation signal output from the feedback signal calculation module is superimposed on the original sinusoidal wave data sequence to form new integer-cycle drive data. This data is then converted again by D / A conversion to output the corrected drive electrical signal, thus forming a closed-loop control. This scheme effectively suppresses harmonic distortion under the ultimate sound pressure range by real-time monitoring of the harmonic components of the sound pressure waveform within the piston cavity and generating inverse compensation signals, achieving the design requirements.

[0024] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A combined excitation type wide-range infrasonic piston sound generating device, characterized in that, include: The system comprises a first piston excitation system (1), a laser vibrometer (2), a second piston excitation system (3), and a rotating bracket (4). The laser vibrometer (2) is mounted on the rotating bracket (4) and positioned between the first piston excitation system (1) and the second piston excitation system (3). The rotating bracket (4) is configured to adjust the measurement direction of the laser vibrometer (2) to align with the first piston excitation system (1) or the second piston excitation system (3) for displacement measurement. The first piston excitation system (1) includes a moving coil speaker (11), a first piston (12), a flexible film (13), a bottom cover (14), a sensor interface (16), and a top cover (17); the top cover (17) is disposed on the bottom cover (14) to form a first piston cavity (15), the moving coil speaker (11) is disposed inside the bottom cover (14), the first piston (12) is fixedly installed on the moving coil speaker (11), the flexible film (13) is pressed by a retaining ring (18) with an edge concave-convex mating structure and fixed to the bottom cover (14) by screws, and the sensor interface (16) is disposed on the top cover (17); The second piston excitation system (3) includes a linear motor (31), an adapter plate (32), a second piston (33), a guide structure (34), and a second piston cavity (35). The linear motor (31) is fixedly connected to the second piston (33) through the adapter plate (32). The second piston (33) is coaxially engaged with the second piston cavity (35) through the guide structure (34). The second piston (33) and the guide structure (34) are sealed by a non-contact gap.

2. The combined excitation wide-range infrasonic piston sound-generating device according to claim 1, characterized in that, The first piston excitation system (1) generates low-distortion standard infrasound in the low sound pressure range of 0.01 Pa to 200 Pa, and the second piston excitation system (3) generates low-distortion standard infrasound in the high sound pressure range of 100 Pa to 10 kPa.

3. The combined excitation wide-range infrasonic piston sound-generating device according to claim 1, characterized in that, The seal (13) is a flexible film that provides a flexible contact seal when the first piston excitation system (1) is in a small displacement condition.

4. The combined excitation wide-range infrasonic piston sound-generating device according to claim 3, characterized in that, When the first piston (12) is installed, it is higher than the mounting plane of the bottom cover (14), so that the flexible film is tightly stretched on the surface of the first piston (12).

5. The combined excitation wide-range infrasonic piston sound-generating device according to claim 1, characterized in that, The second piston excitation system (3) also includes a third piston chamber (36), a slide (37) and a base plate (38). The third piston chamber (36) is mounted on the slide (37) and can be docked and locked or separated from the first piston chamber (35) through the slide (37) to adjust the total volume of the piston chamber. The base plate (38) is provided with an infrasound sensor interface, a temperature sensor interface and a pressure sensor interface.

6. The combined excitation wide-range infrasonic piston sound-generating device according to claim 1, characterized in that, Low-distortion standard infrasound sensors are installed on the outside of the first piston cavity (15), the second piston cavity (35), and the third piston cavity (36) to acquire the output sound pressure signal inside the piston cavity.

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