A standard phase generation and calibration device based on pressure field coupling cavity

Abstract

The present application relates to the technical field of acoustic metrology, and more particularly to a standard phase generation and calibration device based on a pressure field coupling cavity. The present application comprises two end surfaces of an equal-phase plane wave coupling cavity, which are respectively sealed and connected with a receiving microphone and a transmitting microphone. In the equal-phase plane wave coupling cavity, the phase of the sound pressure signal is equal everywhere. A reciprocity phase calibrator is connected with the receiving microphone and the transmitting microphone, and collects voltage, current and phase information of the equal-phase plane wave coupling cavity. A multi-channel sound analyzer is connected with the reciprocity phase calibrator, and is used to measure the phase difference between the transmitting channel and the receiving channel. An output end of a signal source is connected with an input end of the reciprocity phase calibrator. Measuring and control software is connected with the reciprocity phase calibrator and the multi-channel sound analyzer, respectively. The present application proposes a reciprocity method for calibrating the sensitivity and absolute phase, so as to realize the standard phase generation and calibration based on the pressure field coupling cavity.

Description

Technical Field

[0001] This invention relates to the field of acoustic metrology, and more specifically, to a standard phase generation and calibration device based on a pressure field coupling cavity. Background Technology

[0002] Currently, after more than 70 years of in-depth research, the calibration uncertainty of the coupled cavity reciprocity method in the mid-frequency range of 20Hz-20kHz has reached (0.05~0.12)dB (k=2), but the absolute phase calibration of laboratory standard microphones is still in its infancy.

[0003] The laboratory standard condenser microphone is a linear, passive, reversible electroacoustic transducer, and therefore can be considered as a passive four-terminal network, such as... Figure 1 As shown. One end is the "electrical terminal" and the other end is the "acoustic terminal". When current is applied to the electrical terminal, a voltage is generated at the electrical terminal, and a sound wave volume velocity is generated at the acoustic terminal (on the diaphragm); when sound pressure is applied to the acoustic terminal, a sound wave volume velocity is generated at the acoustic terminal (on the diaphragm), and a current and voltage are generated at the electrical terminal.

[0004] The coupled-cavity reciprocity method is based on the reciprocity principle of sound fields and the electromechanical reciprocity principle of microphones. Its device appearance and circuit principle are as follows: Figure 2 As shown.

[0005] It obtains the sensitivity product of the coupled microphones through interactive testing of three microphones (at least two of which are reciprocal microphones), or interactive testing of two microphones (at least one of which is a reciprocal microphone) and a sound source, and then calculates the sound pressure sensitivity of each microphone. Laboratory standard microphones or similar microphones are reciprocal, and according to the reciprocity principle, the two-port equations are satisfied.

[0006] Currently, microphone diaphragms are quite sensitive to changes in environmental parameters, and absolute phase calibration of microphones still presents significant challenges. Summary of the Invention

[0007] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the object of this invention is to provide a standard phase generation and calibration device based on a pressure field coupling cavity, so as to achieve standard phase generation and calibration based on a pressure field coupling cavity.

[0008] To achieve the above and other related objectives, the present invention provides a standard phase generation and calibration device based on a pressure field coupling cavity, comprising: An equiphase plane wave coupling cavity has a receiving microphone and a transmitting microphone sealed at its two ends, respectively. Inside the equiphase plane wave coupling cavity, the phase of the sound pressure signal is equal everywhere. A reciprocal phase calibrator is connected to the receiving microphone and the transmitting microphone, and collects the voltage, current and phase information of the equiphase plane wave coupling cavity; A multi-channel acoustic analyzer, connected to the reciprocal phase calibrator, is used to measure the phase difference between the transmitting and receiving channels; The signal source, the output of which is connected to the input of the reciprocal phase calibrator; The measurement and control software is connected to the reciprocal phase calibrator and the multi-channel acoustic analyzer, respectively.

[0009] In one embodiment of the present invention, it further includes: A preamplifier, one end of which is connected to the receiving microphone, and the other end of which is connected to the reciprocal phase calibrator; An electroacoustic transmitter, one end of which is connected to the transmitting microphone, and the other end of which is connected to the reciprocal phase calibrator.

[0010] In one embodiment of the present invention, the reciprocal phase calibrator includes: A first high-pass filter, one end of which is connected to the preamplifier, and the other end of which is connected to one end of a first amplifier, and the other end of the first amplifier is connected to the multi-channel acoustic analyzer. A second high-pass filter is connected at one end to the electroacoustic transmitter, and at the other end to one end of a second amplifier, which in turn is connected to the multi-channel acoustic analyzer.

[0011] In one embodiment of the present invention, the reciprocal phase calibrator further includes: The third amplifier has one end connected to the first high-pass filter and the other end connected to the multi-channel acoustic analyzer. A fourth amplifier, one end of which is connected to the second high-pass filter, and the other end of which is connected to the multi-channel acoustic analyzer; The fifth amplifier has one end connected to the signal source and the other end connected to the equal-phase plane wave coupling cavity.

[0012] In one embodiment of the present invention, a coupling relationship is established between the volume of the equal-phase plane wave coupling cavity and the front cavity volume of the receiving microphone and the transmitting microphone.

[0013] In one embodiment of the present invention, establishing a coupling relationship between the volume of the equal-phase plane wave coupling cavity and the front cavity volumes of the receiving microphone and the transmitting microphone includes: calculating the sound pressure inside the equal-phase plane wave coupling cavity, calculating the increase in the volume of the equal-phase plane wave coupling cavity, and calculating the relationship between the propagation coefficient and the acoustic impedance of the equal-phase plane wave coupling cavity.

[0014] In one embodiment of the present invention, calculating the equal-phase plane wave coupled cavity includes: The formula for calculating the acoustic pressure inside the equal-phase plane wave coupling cavity is as follows: , Wherein, air density is set Atmospheric pressure Propagation constant cavity volume Piston diameter Piston area Cavity length sound quality , sound Volume velocity .

[0015] In one embodiment of the present invention, the calculation of the increase in the volume of the equal-phase plane wave coupled cavity includes: The increase in the volume of the equiphase plane wave coupled cavity is corrected using a complex correction factor. The formula is as follows: , in, The complex temperature transfer function is defined as the ratio of the spatial average of the sinusoidal temperature change related to sound pressure to the sinusoidal temperature change that might occur if the coupled cavity walls were completely non-thermal. The specific heat ratio under the measurement conditions. The calculation formula is as follows: , , , , , Where R is the ratio of the length to the diameter of the coupling cavity; is the frequency, in Hz; l is the ratio of the coupling cavity volume to its surface area, in m. Thermal diffusivity of a confined gas, in units of .

[0016] In one embodiment of the present invention, the calculation of the relationship between the propagation coefficient and acoustic impedance of the equiphase plane wave coupled cavity includes: The propagation coefficient of the plane wave coupled cavity Harmony and acoustic impedance The relationship is: , , in, This refers to gas viscosity, in units of... ; Where is the radius of the coupling cavity, in meters; c is the speed of sound, in cubic meters per second. ; Angular frequency, unit: ; Density, unit: ; The thermal diffusivity of air, in units of .

[0017] As described above, the standard phase generation and calibration device based on a pressure field coupling cavity of the present invention has the following beneficial effects: The present invention provides a standard phase generation and calibration device based on a pressure field coupling cavity, and proposes a sensitivity absolute phase reciprocity calibration method, thereby realizing standard phase generation and calibration based on a pressure field coupling cavity.

[0018] The present invention provides a standard phase generation and calibration device based on a pressure field coupling cavity, which achieves a wide frequency range: 20Hz-20kHz, and a phase measurement uncertainty U=0.1°~2° (k=2).

[0019] This invention provides a standard phase generation and calibration device based on a pressure field coupling cavity. It conducts research on equiphase plane wave coupling cavities and reciprocal phase calibrators, proposes a sensitivity absolute phase reciprocal calibration method, and achieves accurate calibration of the microphone absolute phase by analyzing the influencing factors of sensitivity absolute phase calibration and designing the measurement process. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a passive four-terminal network of a microphone according to an embodiment of the present invention; Figure 2 This is a schematic diagram of reciprocity calibration according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a standard phase generation and calibration device based on a pressure field coupling cavity according to an embodiment of the present invention; Figure 4 This is a system block diagram of a standard microphone sensitivity phase characteristic standard device based on a pressure field coupling cavity standard phase generation and calibration device according to an embodiment of the present invention; Figure 5 This is a schematic diagram of a plane wave coupling cavity structure of a standard phase generation and calibration device based on a pressure field coupling cavity according to an embodiment of the present invention; Figure 6This is a schematic diagram of a 1-inch coupling cavity (20Hz~12.5kHz) of a standard phase generation and calibration device based on a pressure field coupling cavity according to an embodiment of the present invention.

[0021] Figure 7 This is a schematic diagram of a 1 / 2-inch coupling cavity (20Hz~20kHz) of a standard phase generation and calibration device based on a pressure field coupling cavity according to an embodiment of the present invention; Figure 8 This is a schematic diagram of a 1 / 2-inch coupling cavity (different cavity lengths) of a standard phase generation and calibration device based on a pressure field coupling cavity according to an embodiment of the present invention; Figure 9 This is a schematic diagram of the acoustic pressure numerical model inside the coupling cavity of a standard phase generation and calibration device based on a pressure field coupling cavity according to an embodiment of the present invention; Figure 10 This is a frequency response curve of a 4160 (7.5 mm) coupling cavity of a standard phase generation and calibration device based on a pressure field coupling cavity according to an embodiment of the present invention; Figure 11 This is a frequency response curve of a 4160 (15mm) coupling cavity of a standard phase generation and calibration device based on a pressure field coupling cavity according to an embodiment of the present invention; Figure 12 This is a flowchart of an automatic phase frequency response calibration system based on a standard phase generation and calibration device using a pressure field coupling cavity, according to an embodiment of the present invention. Detailed Implementation

[0022] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0023] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0024] Terms such as "first" or "second" may be used to describe various components, but these components are not limited by the terms described above. The terms described above are used to distinguish one component from another; for example, without departing from the scope of the concept according to this disclosure, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component.

[0025] Furthermore, "connected / linked" indicates that one component is directly electrically connected to another component or indirectly electrically connected through another component. Unless otherwise explicitly stated in the sentence, the singular form may include the plural form. Additionally, the terms "comprising / including" or "containing / including" as used in this specification indicate the presence or addition of one or more components, steps, operations, and elements. Specific structural or functional descriptions of examples of embodiments of the concepts disclosed in this specification are merely illustrative to describe examples of embodiments of the concepts, and examples of embodiments of the concepts can be implemented in various forms, but these descriptions are not limited to the examples of embodiments described in this specification.

[0026] Based on the concept, various modifications and changes can be applied to examples of embodiments, such that examples of embodiments will be illustrated in the accompanying drawings and described in the specification. However, examples of embodiments based on the concept are not limited to specific embodiments, but include all changes, equivalents, or substitutions included within the spirit and scope of this disclosure.

[0027] It should be understood that when describing an element as "connected" or "linked" to another element, the element may be directly connected or linked to the other element, or it may be connected or linked to the other element via a third element. Conversely, it should be understood that when an element is described as "directly connected to" or "directly linked to" another element, no other element is placed between them. Other expressions describing relationships between components (i.e., "between" and "directly between" or "adjacent to" and "directly adjacent to") need to be interpreted in the same way.

[0028] The terminology used in this specification is for the purpose of describing specific examples of implementations only and is not intended to limit this disclosure. The singular form may include the plural form unless there is an explicit contrary meaning in the context. It should be understood in this specification that the terms "comprising" or "having" indicate the presence of the features, quantities, steps, operations, components, parts, or combinations thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, quantities, steps, operations, components, parts, or combinations thereof.

[0029] Unless otherwise defined, all terms used herein (including technical or scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art. If a term is not clearly defined in a common dictionary in this specification, it shall be interpreted as having the same meaning as in the context of the relevant art, and not as an ideal or overly formal meaning.

[0030] Descriptions of known components and processing techniques may be omitted to avoid unnecessarily obscuring the embodiments of this disclosure.

[0031] Throughout this specification, the same reference numerals refer to the same elements. Therefore, even if a reference numeral is not mentioned or described with reference to one drawing, it may be mentioned or described with reference to another drawing. Furthermore, even if a reference numeral is not shown in one drawing, it may be mentioned or described with reference to another drawing.

[0032] Additionally, the logic level of a signal may be different from or opposite to the logic level described. For example, a signal described as having a logic "high" level may optionally have a logic "low" level, and a signal described as having a logic "low" level may optionally have a logic "high" level.

[0033] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this disclosure to facilitate a better understanding of the disclosure. However, the technical solutions claimed in this disclosure can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0034] Currently, after more than 70 years of in-depth research, the calibration uncertainty of the coupled cavity reciprocity method in the mid-frequency range of 20Hz-20kHz has reached (0.05~0.12)dB (k=2), but the absolute phase calibration of laboratory standard microphones is still in its infancy.

[0035] The laboratory standard condenser microphone is a linear, passive, reversible electroacoustic transducer, and therefore can be considered as a passive four-terminal network, such as... Figure 1 As shown. One end is the "electrical terminal," and the other end is the "audio terminal." Current is applied to the electrical terminal. Then, a voltage is generated at the electrical terminal. At the acoustic end (on the diaphragm), a sound wave volume velocity is generated. Apply sound pressure at the sound end Then, sound wave volume velocity is generated at the acoustic end (on the diaphragm). At the electrical terminals, current is generated. and voltage .

[0036] The coupled-cavity reciprocity method is based on the reciprocity principle of sound fields and the electromechanical reciprocity principle of microphones. Its device appearance and circuit principle are as follows: Figure 2 As shown.

[0037] It obtains the sensitivity product of the coupled microphones through interactive tests of three microphones (at least two of which are reciprocal microphones), or interactive tests of two microphones (at least one of which is a reciprocal microphone) and a sound source, and then calculates the sound pressure sensitivity of each microphone. Laboratory standard microphones or similar microphones are reciprocal, and according to the reciprocity principle, the two-port equations are satisfied. Their relationship can be expressed by the following equation: , in: — Microphone terminal voltage (complex number), in V; —The electrical impedance of the microphone diaphragm at rest, in units of ; —The current (complex number) flowing through the microphone terminals, in amperes (A); q—Volume velocity (complex number) through the acoustic end (diaphragm), in m3 / s; —The sound pressure (complex number) acting on the acoustic end diaphragm, in Pa; , —The electroacoustic and electroacoustic conversion coefficients of the microphone; — Acoustic impedance of a microphone with its electrical terminals open, expressed in Pa·s / m3.

[0038] According to the reciprocity principle, the electroacoustic and acoustic-electric conversion coefficients are... and Should meet: , in, It is the complex sound pressure sensitivity of the microphone, and its phase is the absolute phase of the microphone's sensitivity.

[0039] Based on this principle, three standard microphones need to be coupled in pairs, and their electrical and acoustic transfer impedances need to be measured. Three sets of equations can be listed, and the sensitivity absolute phase of the three microphones can be solved by considering the influence and correction of parameters such as ambient temperature, humidity, and air pressure.

[0040] The calculation method is as follows: , The absolute phase of the sensitivity of a standard microphone changes with frequency, so phase response is also an important parameter of a standard microphone.

[0041] Microphone diaphragms are highly sensitive to changes in environmental parameters, and correction methods are typically used to reduce calibration uncertainty. This project will use a temperature and humidity test chamber to study these variations, establish a database of environmental parameter correction values, and assist the automatic phase-frequency response calibration system in calculating calibration results. The range of environmental parameters for the experimental study is as follows: Atmospheric pressure range: (97~103) kPa; Temperature range: (20~25)℃; Relative humidity range: (35~75)%RH.

[0042] The method for calculating the microphone phase sensitivity is as follows: (4) (5) In the formula: —The sound pressure phase sensitivity of microphone “n” is not corrected for the front cavity volume; —The sound pressure phase sensitivity of microphone “n” after correction for the front cavity volume; —Phase difference correction for the voltage acquisition channel of microphone “n”; —Cavity volume correction; —Static pressure correction; —Reference phase; — Correction of the front cavity volume of microphone “n”.

[0043] The principle and device composition of the coupled-cavity reciprocity method (absolute method) for sound pressure phase calibration: The coupled-cavity reciprocity method (absolute method) acoustic pressure phase standard device mainly consists of a coupled cavity, a preamplifier, a reciprocity phase calibrator, a multi-channel acoustic (phase) analyzer, a signal source, and measurement and control software. Among these components, the equiphase plane wave coupled cavity and the reciprocity phase calibrator are the main research contents, and the sensitivity phase reciprocity method calibration method is one of the key technologies. Figure 3 This is a schematic diagram of a standard phase generation and calibration device based on a pressure field coupling cavity according to an embodiment of the present invention. Figure 4 This is a system block diagram of a standard microphone sensitivity phase characteristic standard device based on a pressure field coupling cavity standard phase generation and calibration device according to an embodiment of the present invention.

[0044] (1) Equal-phase plane wave coupled cavity The equal-phase plane wave coupling cavity is the core component of the entire calibration device, and its structural principle is as follows: Figure 5 As shown. Within the coupling cavity, the phase of the sound pressure signal must be equal everywhere. It is essential to ensure that the sound pressure phase received by the two microphones within the cavity is completely consistent. This places high demands on the structural design and machining process of the coupling cavity: the connection between the coupling cavity and the microphone must be well sealed, requiring sound insulation and vibration isolation design, with a sound insulation of at least 30dB; the volume of the coupling cavity and the volume of the microphone's front cavity need to be coupled; and for the two laboratory standard microphones LS1P and LS2P, two sets of plane wave coupling cavities, one long and one short, suitable for different measurement frequency ranges, are designed respectively. Figure 6 It has a 1-inch coupling cavity (20Hz~12.5kHz). Figure 7 It is a 1 / 2-inch coupling cavity (20Hz~20kHz). Figure 8 For 1 / 2-inch coupling cavities (different cavity lengths).

[0045] The intracavitary sound pressure is calculated as shown in equation (6).

[0046] , Wherein, air density is set Atmospheric pressure Propagation constant (specific heat ratio) cavity volume Piston diameter Piston area Cavity length sound quality , sound Volume velocity The theoretical calculation results of the amplitude and phase of the sound pressure inside the cavity are as follows: Figure 9 As shown.

[0047] (2) Analysis of factors affecting absolute phase calibration of sensitivity In addition to correcting for cavity volume and static pressure, the absolute phase calibration of sensitivity should also consider corrections for heat conduction and acoustic leakage in the coupling cavity at low frequencies, and phase deviation corrections introduced by viscous losses within the cavity at high frequencies. The specific correction principles and methods are briefly described below: Before considering the effects of acoustic leakage in the coupling cavity, it is necessary to determine the impact of heat conduction on low-frequency reciprocity calibration. At higher frequencies, the process within the coupling cavity can be considered adiabatic, and heat conduction can be ignored. As the frequency decreases, heat conduction between the air and the cavity walls in the sealed coupling cavity causes the adiabatic conditions to gradually transition to isothermal conditions. The accuracy of this transition depends on the calibration frequency and the size of the coupling cavity. The sound pressure generated by the transmitting microphone, i.e., a constant-volume and displaced sound source, also changes accordingly. This effect can be understood as an increase in the volume of the coupling cavity, using a complex correction factor. It is expressed as follows: , In the formula, The complex temperature transfer function is defined as the ratio of the spatial average of the sinusoidal temperature change related to sound pressure to the sinusoidal temperature change that might occur if the coupled cavity walls were completely non-thermal. This is the specific heat ratio under the measurement conditions. IEC 61094-2 provides... Specific calculation method: , , , , , Where R is the ratio of the length to the diameter of the coupling cavity; is the frequency, in Hz; l is the ratio of the coupling cavity volume to its surface area, in m. Thermal diffusivity of a confined gas, in units of .

[0048] Table 1: Complex values ​​of temperature transfer function

[0049] Between 2 and 20 Hz, the thermal conductivity correction factor gradually decreases with increasing coupled cavity length, and the shorter the coupled cavity length, the greater the uncertainty caused by thermal conductivity. Therefore, considering the impact on thermal conductivity, a longer coupled cavity makes low-frequency reciprocity calibration more stable than a shorter coupled cavity.

[0050] The impact of acoustic leakage in a coupled cavity system is related to the flatness of the microphone's front surface, the flatness of the two end faces of the coupled cavity, and the tightness of the capillary blockage. In a coupled cavity system, acoustic leakage cannot be directly calculated theoretically; its influence must be explored experimentally. Among these, the 7.5mm and 15mm coupled cavities are two commonly used coupled cavities in existing coupled cavity sound pressure standards. The frequency response curve of the measured 4160 laboratory standard microphone is shown in the figure below. Figure 10 , Figure 11As shown in the figure. Theoretically, the capillary tube, after being plugged with a thin metal rod, should conform to the solid curve in the figure. However, due to potential tolerances in the manufacturing of the coupling cavity, capillary tube, and thin metal rod, if there are minute gaps at the contact surface between the coupling cavity and the microphone, or if there are also minute gaps in the working relationship between the capillary tube and the thin metal rod, acoustic leakage is highly likely to occur during low-frequency measurements. Treating the capillary tube with a sealing material confirmed the previous hypothesis, and the experimental results improved significantly. The experimental results show that the sealing degree of the coupling cavity capillary tube does indeed have a significant impact on the experimental results at around 2Hz due to acoustic leakage.

[0051] At higher frequencies, in addition to thermal losses, viscous losses also exist. The viscous effect of the boundary layer near the surface reduces the effective cross-sectional area of ​​the coupler, while the decrease in sound velocity increases the effective length of the coupler. When thermal conduction effects still exist, these two effects compensate for each other. Based on Kirchhoff's theory explaining the combined effects of thermal conduction and viscous losses on sound propagation within a cylindrical tube, the propagation coefficient of the coupling cavity can be derived. Harmony and acoustic impedance The complex expression is as follows: , , in, This refers to gas viscosity, in units of... ; Where is the radius of the coupling cavity, in meters; c is the speed of sound, in cubic meters per second. ; Angular frequency, unit: ; Density, unit: ; The thermal diffusivity of air, in units of .

[0052] In summary, to meet the overall objective of phase measurement uncertainty U=0.1°~2° (k=2), this project proposes to use thermal conduction and acoustic leakage correction methods in the coupling cavity in the low frequency band, and to consider a comprehensive correction method of thermal conduction and viscous loss in the high frequency band. The correction reference values ​​are shown in Table 2, so as to achieve the purpose of accurate calibration of the microphone absolute phase.

[0053] Table 2: Correction reference values ​​introduced by heat conduction and sound leakage, etc.

[0054] Because microphones operate over a wide frequency range (20Hz~20kHz), automatic measurement methods are typically used to calibrate their phase response characteristics. This project will develop an automatic phase response calibration system by incorporating an environmental parameter correction database. The flowchart of the coupled-cavity reciprocity method system is shown below. Figure 12 As shown.

[0055] In summary, the present invention provides a standard phase generation and calibration device based on a pressure field coupling cavity, and proposes a sensitivity absolute phase reciprocity calibration method, thereby realizing standard phase generation and calibration based on a pressure field coupling cavity.

[0056] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A standard phase generation and calibration device based on a pressure field coupled cavity, characterized in that, include: An equiphase plane wave coupling cavity has a receiving microphone and a transmitting microphone sealed at its two ends, respectively. Inside the equiphase plane wave coupling cavity, the phase of the sound pressure signal is equal everywhere. A reciprocal phase calibrator is connected to the receiving microphone and the transmitting microphone, and collects the voltage, current and phase information of the equiphase plane wave coupling cavity; A multi-channel acoustic analyzer, connected to the reciprocal phase calibrator, is used to measure the phase difference between the transmitting and receiving channels; The signal source, the output of which is connected to the input of the reciprocal phase calibrator; The measurement and control software is connected to the reciprocal phase calibrator and the multi-channel acoustic analyzer, respectively.

2. The standard phase generation and calibration device based on a pressure field coupling cavity according to claim 1, characterized in that, Also includes: A preamplifier, one end of which is connected to the receiving microphone, and the other end of which is connected to the reciprocal phase calibrator. An electroacoustic transmitter, one end of which is connected to the transmitting microphone, and the other end of which is connected to the reciprocal phase calibrator.

3. The standard phase generation and calibration device based on a pressure field coupling cavity according to claim 2, characterized in that, The reciprocal phase calibrator includes: A first high-pass filter, one end of which is connected to the preamplifier, and the other end of which is connected to one end of a first amplifier, and the other end of the first amplifier is connected to the multi-channel acoustic analyzer. A second high-pass filter is connected at one end to the electroacoustic transmitter, and at the other end to one end of a second amplifier, which in turn is connected to the multi-channel acoustic analyzer.

4. The standard phase generation and calibration device based on a pressure field coupling cavity according to claim 3, characterized in that, The reciprocal phase calibrator also includes: The third amplifier has one end connected to the first high-pass filter and the other end connected to the multi-channel acoustic analyzer. A fourth amplifier, one end of which is connected to the second high-pass filter, and the other end of which is connected to the multi-channel acoustic analyzer; The fifth amplifier has one end connected to the signal source and the other end connected to the equal-phase plane wave coupling cavity.

5. The standard phase generation and calibration device based on a pressure field coupling cavity according to claim 1, characterized in that: The equal-phase plane wave coupling cavity volume is coupled with the front cavity volume of the receiving microphone and the transmitting microphone.

6. The standard phase generation and calibration device based on a pressure field coupling cavity according to claim 5, characterized in that, Establishing a coupling relationship between the volume of the equal-phase plane wave coupling cavity and the front cavity volumes of the receiving microphone and the transmitting microphone includes: calculating the sound pressure inside the equal-phase plane wave coupling cavity, calculating the increase in the volume of the equal-phase plane wave coupling cavity, and calculating the relationship between the propagation coefficient and the acoustic impedance of the equal-phase plane wave coupling cavity.

7. A standard phase generation and calibration device based on a pressure field coupling cavity according to claim 6, characterized in that: The calculation of the equal-phase plane wave coupled cavity includes: The formula for calculating the acoustic pressure inside the equal-phase plane wave coupling cavity is as follows: ， Wherein, air density is set Atmospheric pressure propagation constant cavity volume Piston diameter Piston area Cavity length sound quality , sound Volume velocity .

8. A standard phase generation and calibration device based on a pressure field coupling cavity according to claim 6, characterized in that: The calculation of the increase in the volume of the equal-phase plane wave coupled cavity includes: The increase in the volume of the equiphase plane wave coupled cavity is corrected using a complex correction factor. The formula is as follows: ， in, The complex temperature transfer function is defined as the ratio of the spatial average of the sinusoidal temperature change related to sound pressure to the sinusoidal temperature change that might occur if the coupled cavity walls were completely non-thermal. The specific heat ratio under the measurement conditions. The calculation formula is as follows: ， ， ， ， ， Where R is the ratio of the length to the diameter of the coupling cavity; is the frequency, in Hz; l is the ratio of the coupling cavity volume to its surface area, in m. Thermal diffusivity of a confined gas, in units of .

9. A standard phase generation and calibration device based on a pressure field coupling cavity according to claim 6, characterized in that: The calculation of the relationship between the propagation coefficient and acoustic impedance of the equal-phase plane wave coupled cavity includes: The propagation coefficient of the plane wave coupled cavity Harmony and acoustic impedance The relationship is: ， ， in, Gas viscosity, unit: ; Where is the radius of the coupling cavity, in meters; c is the speed of sound, in cubic meters per second. ; Angular frequency, unit: ; Density, unit: ; The thermal diffusivity of air, in units of .

Images