Sound absorption coefficient measuring device

Abstract

The invention relates to the field of noise and vibration control service in the advanced environmental protection industry, in particular to an acoustic absorption coefficient measuring device. The sound absorption coefficient measuring device comprises a sound source cavity and a reverberation cavity which are mutually independent; the composite acoustic coupling channel is communicated between the sound source cavity and the reverberation cavity and comprises a gradually-shrunk configuration section, and the radial size of the longitudinal section of the gradually-shrunk configuration section is gradually reduced from the interior of the sound source cavity; the radial size of the longitudinal section of the stable configuration section is not changed from the tail end of the gradually-shrunk configuration section to the interior of the reverberation cavity; wherein both the tapered configuration section and the stable configuration section are arranged about a common linear central axis. The large-scale limitation of a traditional reverberation chamber is broken through, a special testing system for the centimeter-level acoustic sample piece is developed, measurement of the random incidence sound absorption coefficient of the small-size sample piece is achieved, and the blank of acoustic measurement of the small-size acoustic sample piece is filled up.

Description

Technical Field

[0001] The present invention relates to the field of noise and vibration control services in advanced environmental protection industries, and in particular to a sound absorption coefficient measuring device. Background Art

[0002] The sound absorption coefficient is a core parameter that characterizes the acoustic properties of materials. Its precise measurement has irreplaceable practical value for architectural acoustics, noise control and the research and development of new acoustic materials. At present, the internationally used sound absorption coefficient measurement methods are mainly the standing wave tube method and the reverberation chamber method. The standing wave tube method only reflects the vertical incidence characteristics of the material at a specific frequency, which is significantly different from the sound absorption behavior of the material in the real environment, making it difficult for the measurement results to directly guide actual engineering applications. The reverberation chamber method calculates the sound absorption coefficient of the material under random incidence conditions by comparing the changes in the reverberation time of the room with and without samples. Its measurement results are closer to the actual performance of the material in a complex sound environment. Traditional reverberation chambers generally require the specimen area to be 10-12m 2 This makes some small-sized acoustic materials (such as automotive interior parts, precision instrument sound-absorbing components, and trace biological samples) unable to meet the requirements of measurement specifications, which is in sharp contradiction with the current trend of miniaturization of acoustic materials. Summary of the Invention

[0003] 1. Technical Problems to be Solved

[0004] The present invention is intended to at least partially solve one of the above technical problems.

[0005] 2. Technical Solution

[0006] The present invention provides a device for measuring sound absorption coefficients. The device comprises: a mutually independent sound source cavity and a reverberation cavity; a composite acoustic coupling channel connected between the sound source cavity and the reverberation cavity, comprising: a tapered section, the radial dimension of whose longitudinal cross-section gradually decreases from the inside of the sound source cavity; and a stable section, the radial dimension of whose longitudinal cross-section remains constant from the end of the tapered section to the inside of the reverberation cavity; wherein the tapered section and the stable section are arranged around a common linear central axis.

[0007] 3. Beneficial Effects

[0008] It can be seen from the above technical solutions that the present invention has at least one of the following beneficial effects compared to the prior art:

[0009] ① The present invention breaks through the large-scale limitations of traditional reverberation chambers and develops a dedicated testing system for centimeter-level acoustic samples, realizing the measurement of random-incidence sound absorption coefficients of tiny-sized samples, thus filling the gap in acoustic measurement of small-sized acoustic samples.

[0010] ② In the present invention, by limiting the shape structure, size ratio, sound-absorbing surface and other parameters of the reverberation chamber, the audible sound range limitation of the traditional reverberation chamber is broken through, and the effective measurement frequency band is expanded to the ultrasonic domain, providing a high-frequency sound absorption characteristic characterization solution for cutting-edge fields such as micro-acoustic metamaterials and MEMS devices.

[0011] ③ In the present invention, the hemispherical scatterers randomly distributed on the inner wall enhance the multi-directional diffuse reflection of sound waves and suppress the formation of high-frequency standing waves, thereby ensuring the uniformity of sound field diffusion.

[0012] ④ The present invention sets the reverberation chamber and the sound source chamber independently, and integrates the broadband sound-generating device into an independently sealed sound source chamber. The physical isolation design can reduce the background noise and ensure the airtightness of the experimental environment.

[0013] ⑤ In the present invention, the tapered segment directs the sound energy radiated from the sound-generating device into the stable segment, achieving focused sound beams and avoiding energy loss due to sound wave divergence. The stable segment connects to the top diameter of the tapered segment, with its axis perpendicular to the corresponding joint surface of the reverberation chamber. This constrains the sound wave to enter in a near-point source form, ensuring the uniformity of the diffuse sound field within the reverberation chamber. Thus, the composite acoustic coupling channel of the tapered segment and the stable segment achieves the dual optimization of "efficient directional transmission of sound energy" and "precise excitation of a point source."

[0014] ⑥ In certain embodiments of the present invention, the reverberation chamber and the sound source chamber are seamlessly bonded to form a rigid integrated structure, thereby ensuring the mechanical stability of the system and improving the convenience of experimental operation.

[0015] ⑦ In certain embodiments of the present invention, quick-detachable sealing covers are provided on the top of the reverberation chamber and the right side wall of the sound source chamber. Rubber sealing strips are embedded in the edge of the cover, and the sealing cover and the cavity are fastened by stainless steel buckles, thereby ensuring the convenience of experimental operation and the airtightness of the experimental environment.

[0016] ⑧ The applicant discovered that the oxygen in the air would cause great loss to the ultrasonic frequency sound waves targeted by the sound absorption coefficient measuring device of the present invention.

[0017] Based on this, the applicant added an atmosphere-forming component to the reverberation chamber, thereby avoiding the loss of ultrasonic waves by oxygen in the air and realizing the measurement of the ultrasonic frequency sound wave absorption coefficient.

[0018] ⑨ In certain embodiments of the present invention, the acoustic sensor can be reliably fixed in three dimensions within the reverberation chamber through the customized bending of the bending-type acoustic sensor bracket, thereby improving the flexibility of the experiment and reducing the experimental cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the structure of the sound absorption coefficient measuring device according to an embodiment of the present invention.

[0020] Figure 2 for Figure 1 Schematic diagram of the physical part of the sound absorption coefficient measurement device shown.

[0021] Figure 3 for Figure 1 The spatial distribution of the average sound pressure level of different plane spectra in the reverberation chamber sound field of the sound absorption coefficient measurement device shown.

[0022] Figure 4 for Figure 1 The sound field distribution of the sound absorption coefficient measurement device at different positions in the reverberation chamber at a frequency of 20 kHz.

[0023] Figure 5 for Figure 1 Statistical distribution of sound pressure components and amplitudes in the reverberation chamber of the sound absorption coefficient measurement device shown. DETAILED DESCRIPTION

[0024] Before describing specific embodiments of the present invention, it is helpful to define some specific terms.

[0025] The "starting point" mentioned in this article refers to the end where the sound wave starts according to the direction of sound wave transmission; similarly, the "end point" mentioned in this article refers to the end where the sound wave arrives.

[0026] The "sound source chamber" and "reverberation chamber" described herein refer to an interior chamber and the outer enclosure that forms the interior chamber. Specifically, the reverberation chamber includes: an inner rectangular chamber; and an outer PMMA sheet enclosure that forms the rectangular chamber.

[0027] The purpose of this invention is to construct a specialized small reverberation chamber testing system using the reverberation measurement principle. This system can measure the sound absorption of centimeter-scale acoustic samples, providing fundamental technical support for cutting-edge fields such as micro-acoustic metamaterial design and acoustic testing of biological samples. It aims to address the technical challenges of acoustic measurement of tiny samples, which are difficult to achieve in traditional reverberation chambers.

[0028] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific implementation methods and with reference to the accompanying drawings.

[0029] The invention provides a device for measuring a sound absorption coefficient. Figure 1 FIG. 1 is a schematic diagram of the structure of the sound absorption coefficient measuring device according to an embodiment of the present invention. Figure 1 As shown, the sound absorption coefficient measuring device of this embodiment includes:

[0030] Main control module;

[0031] Independent sound source cavity and reverberation cavity;

[0032] A composite acoustic coupling channel is connected between the sound source cavity and the reverberation cavity;

[0033] The signal transmitting module includes: an ultrasonic player and a loudspeaker arranged in the sound source cavity, and is used to continuously and periodically transmit an excitation signal to the reverberation cavity through the loudspeaker according to the instructions of the main control module;

[0034] The signal acquisition module includes: a power amplifier, a data acquisition card and a microphone arranged in the reverberation chamber, which is used to upload the feedback signal collected by the microphone to the main control module, wherein the microphone is placed in the reverberation chamber.

[0035] Those skilled in the art will appreciate that the physical components of the aforementioned sound absorption coefficient measurement device, including the sound source chamber, reverberation chamber, and composite acoustic coupling channel, can be manufactured, sold, or offered for sale independently of the measurement components, including the main control module, signal transmission module, and signal acquisition module. Therefore, these physical components alone are also within the scope of protection of the present invention.

[0036] The following describes in detail the various components of the sound absorption coefficient measuring device of this embodiment.

[0037] Figure 2 for Figure 1 The diagram of the physical part of the sound absorption coefficient measurement device is shown. Figure 1 and Figure 2 , the physical part includes:

[0038] Mutually independent reverberation chamber 1 and sound source chamber 2;

[0039] The composite acoustic coupling channel is connected between the sound source cavity and the reverberation cavity, and includes:

[0040] The truncated cone section 4 has a radial dimension of a longitudinal section that gradually decreases starting from the sound source cavity;

[0041] The cylindrical section 3 has a longitudinal section with a constant radial dimension from the end of the tapered section to the inside of the reverberation cavity;

[0042] The frustum segment and the cylinder segment are both arranged around a common linear central axis.

[0043] In this embodiment, both reverberation chamber 1 and sound source chamber 2 are constructed from approximately 20mm thick polymethyl methacrylate (PMMA) sheets. The adjacent walls of sound source chamber 2 and reverberation chamber 1 are seamlessly bonded to form a rigid, integrated structure. Both reverberation chamber 1 and sound source chamber 2 have rectangular interiors. The three dimensions of the rectangular interior of the reverberation chamber range from 6cm to 12cm.

[0044] Those skilled in the art should understand that the above are only preferred embodiments of the present invention, and the present invention is not limited thereto. In other embodiments of the present invention, the sound source cavity and the reverberation cavity may also be made of other materials with a sound reflection coefficient higher than 94% and a wall thickness greater than 10 mm. In other embodiments of the present invention, the dimensions of the rectangular cavity inside the reverberation cavity may also be between 5 cm and 50 cm in three dimensions. In other embodiments of the present invention, the cavity inside the sound source cavity may also be other shapes, such as: cylindrical, regular polygonal column, etc. These deformation methods can also implement the present invention and are also within the scope of protection of the present invention.

[0045] It can be seen that the present invention breaks through the large-scale limitations of traditional reverberation chambers, develops a special testing system for centimeter-level acoustic samples, realizes the measurement of random incidence sound absorption coefficients of tiny-sized samples, and fills the gap in acoustic measurement of small-sized acoustic samples.

[0046] Furthermore, the present invention independently sets the reverberation chamber and the sound source chamber, and integrates the broadband speaker into the independently sealed sound source chamber. The physical isolation design can reduce the background noise and ensure the airtightness of the experimental environment.

[0047] Furthermore, the reverberation cavity and the sound source cavity of the present invention adopt a seamless bonding process to form a rigid integrated structure, which ensures the mechanical stability of the system and improves the convenience of experimental operation.

[0048] In the present invention, the sound absorbing surface of the rectangular chamber inside the reverberation chamber and the cutoff frequency satisfy the following relationship:

[0049]

[0050] Where A is the total sound absorption, n is the number of types of sound-absorbing surfaces with different sound absorption coefficients, S i The sound absorption coefficient is α i is the surface area of ​​the reverberation cavity, and V is the total volume of the rectangular cavity inside the reverberation cavity.

[0051] In addition to meeting the above cutoff frequency requirements, in this embodiment, in order to avoid the degeneracy of the sound waves, the size ratios of the three dimensions of the rectangular chamber inside the reverberation cavity need to roughly meet

[0052] Please continue to refer to Figure 2 , randomly stick N hemispherical scatterers on the bottom surface and three side surfaces of the reverberation cavity, N ≥ 3. The N hemispherical scatterers can suppress the formation of high-frequency standing waves and improve the uniformity of sound field diffusion.

[0053] Based on the above conditions, numerical simulation verification was performed. In this embodiment, the cutoff frequency of the reverberation chamber 1 is about 18 kHz, and the measurement frequency range is 20 kHz-120 kHz:

[0054] It can be seen that the present invention breaks through the audible sound range limitations of traditional reverberation chambers by limiting parameters such as the shape structure, size ratio, and sound-absorbing surface of the reverberation chamber, and expands the effective measurement frequency band to the ultrasonic domain. While ensuring the uniformity of broadband sound field diffusion, it provides a high-frequency sound absorption characteristic characterization solution for cutting-edge fields such as micro-acoustic metamaterials and MEMS devices, filling the technical gap in small-scale acoustic testing.

[0055] In this embodiment, the truncated cone section 4 of the composite acoustic coupling channel is formed in the corresponding walls of the sound source cavity and the reverberation cavity; the cylindrical section 1 is formed in the corresponding wall of the reverberation cavity, and the starting end of the cylindrical section is connected to the end of the truncated cone section.

[0056] Those skilled in the art will appreciate that while the acoustic coupling channels of the frustoconical and cylindrical segments in this embodiment are directly formed within the corresponding walls of the sound source and reverberation chambers, the present invention is not limited thereto. In other embodiments of the present invention, frustoconical and cylindrical segments having corresponding configurations may be independently formed and then attached to the sound source and reverberation chambers to achieve a specific form of communication between the sound source and reverberation chambers, thereby similarly achieving the present invention and remaining within the scope of protection of the present invention.

[0057] Those skilled in the art will appreciate that while this embodiment employs a truncated cone-cylindrical composite acoustic coupling channel, the present invention is not limited thereto. In other embodiments of the present invention, the truncated cone segment may be replaced by a channel segment having another tapered configuration, such as a regular N-sided pyramid; and the cylindrical segment may be replaced by a regular N-sided prism, and the present invention can still be implemented and fall within the scope of protection of the present invention.

[0058] In this invention, the tapered section directs the sound energy radiated by the loudspeaker into the stable section, achieving focused sound beams and avoiding energy loss due to sound wave divergence. The stable section connects to the top diameter of the tapered section, with its axis perpendicular to the corresponding joint surface of the reverberation chamber. This constrains the sound wave to enter in a near-point source fashion, ensuring uniformity of the diffuse sound field within the reverberation chamber. Thus, the composite acoustic coupling channel of the tapered section and the stable section achieves the dual optimization of "efficient directional transmission of sound energy" and "precise excitation of a point source."

[0059] In this embodiment, the reverberation cavity is filled with an inert atmosphere; the radius d / 2 of the cylindrical segment must satisfy the acoustic cutoff frequency constraint:

[0060]

[0061] Where c is the sound velocity of the inert gas in the reverberation cavity under the experimental environment, f max The upper limit frequency of the applicable frequency band of the reverberation room.

[0062] Furthermore, in order to significantly improve the sound energy input efficiency and signal-to-noise ratio in the reverberation chamber and ensure that the sound field excitation intensity in the reverberation chamber meets the test requirements, the sound field distribution characteristics in the reverberation chamber were analyzed through finite element simulation, and the sound field at a distance of 0.5l from the sound source was extracted. min The sound pressure level (SPL) at the distance is used as the evaluation index. The results show that when the length of the cylindrical section l≈5mm, When the spectrum average value is guaranteed in the whole frequency band: SPL ≥ 65dB (f min ≤f≤f max ), so that a higher signal-to-noise ratio can be obtained to meet the test requirements.

[0063] In the above formula, l min is the minimum of the three dimensions of the reverberation chamber, l is the length of the cylindrical segment, d is the diameter of the longitudinal section at the end of the truncated cone segment, which is equal to the diameter of the longitudinal section of the cylindrical segment, and d' is the diameter of the longitudinal section at the beginning of the truncated cone segment. Furthermore, l≈5mm, with a fluctuation of 10%, i.e., 4.5≤l≤5.5, can be used to implement the present invention and is also within the scope of protection of the present invention.

[0064] Please continue to refer to Figure 2 The reverberation chamber comprises: a reverberation chamber body, which opens upward; and a removable sealing cover 5, which is located on the opening side of the reverberation chamber body and locked to the reverberation chamber body via snaps. An elastic sealing ring is provided at the contact point between the two, forming an airtight interface. Stainless steel snaps are evenly distributed along all four sides of the wall, ensuring a good seal and facilitating experimental operations.

[0065] Please continue to refer to Figure 2 The sound source chamber comprises a sound source chamber body with an open side; and a sound source chamber sealing cover 8, which is removably mounted on the open side of the sound source chamber body and locked to the sound source chamber body via snaps. An elastic sealing ring is provided at the contact point between the two, forming an airtight interface. Stainless steel snaps are evenly distributed along all four sides of the wall, ensuring a good seal and facilitating experimental operation.

[0066] The applicant has found that oxygen in the air can significantly damage the ultrasonic frequency sound waves targeted by the sound absorption coefficient measurement device of this embodiment, seriously affecting the test results. Therefore, an inert atmosphere is more conducive to the measurement of ultrasonic frequency sound absorption coefficients.

[0067] In this embodiment, the reverberation chamber 1 is filled with nitrogen atmosphere. Figure 2 As shown, the reverberation chamber sealing cover 5 symmetrically defines two air guide valve mounting holes 6. The sound absorption coefficient measuring device further includes: an atmosphere forming component; the atmosphere forming component includes:

[0068] An inert gas source with its own first barometer;

[0069] An air inlet valve is installed in the air inlet valve mounting hole, with its air inlet end connected to the inert gas source and its air outlet connected to the interior of the reverberation chamber;

[0070] An air outlet valve is installed in the air outlet valve installation hole, with its air inlet connected to the interior of the reverberation chamber and its air outlet connected to the atmosphere or an exhaust gas collection container;

[0071] The second barometer is connected to the reverberation cavity.

[0072] Among them, the air inlet valve and air outlet valve are standard two-way valves, which support the filling / exhaust of nitrogen to control the gas density inside the cavity and reduce the loss of sound waves inside the cavity.

[0073] Those skilled in the art will appreciate that the nitrogen atmosphere described above is merely an example and the present invention is not limited thereto. In other embodiments of the present invention, other inert atmospheres, such as helium, may also be employed to similarly reduce ultrasonic frequency sound wave losses and are thus within the scope of the present invention.

[0074] In this embodiment, two microphone cable holes 7 are reserved on the reverberation chamber sealing cover 5. Because the reverberation chamber sealing cover is rectangular, it can be rotated 180 degrees and still be buckled. Therefore, the microphone can collect sound pressure at multiple points, covering the four quadrants of the cavity sound field space, thereby increasing the flexibility of microphone arrangement.

[0075] During testing, the front end of the microphone cable is connected to the microphone, and the rear end is led out of microphone cable hole 7. The sound absorption coefficient measurement device also includes a foldable microphone bracket that extends from the microphone cable hole into the reverberation chamber. The top of the bracket secures the microphone and allows the user to freely bend it to define the top microphone position. The customizable folding of the foldable microphone bracket allows for reliable three-dimensional fixation of the microphone within the reverberation chamber, increasing experimental flexibility while reducing experimental costs.

[0076] Those skilled in the art will appreciate that the number of microphone cable holes can be adjusted as needed. Furthermore, the microphone holder's fixing point can be set at a specific location within the reverberation chamber, or different types of microphone holders can be provided, such as a movable microphone holder with a separate base. These variations can also implement the present invention and are within the scope of protection of the present invention.

[0077] Inside the sound source cavity, the speaker's sound radiating end is coaxially aligned with the tapered section, facing the cavity's opening. A speaker cable hole 9 is provided in the cavity's sealing cover for routing the speaker's power and signal cables. The speaker's related cables are connected to the speaker at the front and exit through the speaker cable hole 9.

[0078] Please continue to refer to Figure 1In this embodiment, the sound absorption coefficient measuring device includes: a physical part and a measuring part. The measuring part includes: a main control module, a signal transmission module, and a signal acquisition module.

[0079] In this embodiment, the signal transmission module includes an ultrasonic player and a broadband speaker, which are sequentially connected to a computer to continuously and periodically transmit excitation signals into the reverberation chamber. The broadband speaker is fixed within the sound source cavity, with its radiating end coaxially aligned with the base diameter of the conical section of the composite acoustic coupling channel.

[0080] In this embodiment, the signal acquisition module includes a power amplifier, a data acquisition card, and a 1 / 8-inch CCP microphone connected in sequence by a chassis to complete the real-time acquisition of the sound pressure signal inside the reverberation chamber and send the collected signal to the signal processing module.

[0081] Those skilled in the art will appreciate that, in practical scenarios, other types of acoustic sensors may be used in place of the microphone in this embodiment, and other types of sound-generating devices may be used in place of the speaker in this embodiment. These variations can also implement the present invention and are within the scope of protection of the present invention.

[0082] In this embodiment, the main control module is a main control computer. The main control computer internally includes:

[0083] Signal processing module, responsible for processing the excitation signal and feedback signal;

[0084] The result display module includes: a time domain sound pressure waveform display unit, a frequency domain sound pressure spectrum display unit and a frequency domain sound pressure level characteristic curve unit, which are respectively used to generate and display the time domain sound pressure curve waveform, the frequency domain sound pressure spectrum and the frequency domain sound pressure level characteristic curve.

[0085] Those skilled in the art will appreciate that the above experimental results are merely examples. In actual scenarios, other operations may be performed using the signals from the speaker and microphone to obtain other meaningful data results, which are also within the scope of protection of the present invention.

[0086] To verify that the spatial uniformity and statistical characteristics of the reverberation chamber sound field of the sound absorption coefficient measurement device of this embodiment meet the requirements of the acoustic reverberation field, numerical simulation and statistical analysis are performed, and the specific implementation steps are as follows:

[0087] (1) Sound field diffusivity verification

[0088] The standard deviation of the sound pressure level is considered an important indicator of field diffusion. Six different locations within reverberation chamber 1 were selected and sound pressure data were collected within the frequency range f1 = 20 kHz to f2 = 120 kHz using the commercial finite element software COMSOL. The average sound pressure level (SPL) for each plane spectrum was calculated using the following expression:

[0089]

[0090] where p(f) is the sound pressure at frequency f.

[0091] Based on this, the average sound pressure level (SPL) of each plane spectrum is calculated. Figure 3 for Figure 1 The spatial distribution of the average sound pressure level of different plane spectra in the reverberation cavity sound field of the sound absorption coefficient measurement device shown in the figure. Figure 3 As shown. The SPL is quite flat in space, with only some random fluctuations: Spatial Average Sound Pressure Level σ(SPL) = 0.55dB. The standard deviations of each plane are significantly lower than the 1.5dB threshold specified in ISO374, proving that the sound field in the reverberation chamber has sufficient diffusivity.

[0092] (2) Statistical property verification

[0093] In order to further analyze the statistical properties of the sound field, the sound field distribution at different positions in the reverberation cavity at a frequency of 20 kHz was obtained by two-dimensional scanning. Figure 4 for Figure 1 The sound field distribution of different positions in the reverberation chamber at a frequency of 20kHz using the sound absorption coefficient measurement device shown in the figure. Statistical analysis of the components and amplitudes of the sound pressure is performed, and the results are shown in the figure below. Figure 5 shown. Figure 5 for Figure 1 The statistical distribution of the sound pressure components and amplitudes in the reverberation chamber of the sound absorption coefficient measurement device shown in the figure. The results show that the real part Re(p) and the imaginary part Im(p) of the sound pressure satisfy the Gaussian distribution. Sound pressure amplitude Satisfies Rayleigh distribution Satisfy the statistical law of ideal diffusion field sound pressure distribution.

[0094] Thus, the various embodiments of the present invention have been introduced. According to the above description, those skilled in the art should have a clear understanding of the present invention.

[0095] It should be noted that for certain implementation methods, if they are not the key content of the present invention and are well known to ordinary technicians in the relevant technical field, due to space limitations, they are not described in detail in the drawings or text of the specification. In this case, reference can be made to relevant existing technologies for understanding.

[0096] For the numerical values ​​and numerical ranges mentioned in the present invention, unless expressly indicated to the contrary, the numerical parameters in the description and claims of the present invention may be approximate values ​​and may vary according to the content of the present invention. Specifically, all numbers representing the content of compositions, reaction conditions, etc. recorded in the description and claims should be understood to be modified by the term "about" in all cases, and the meaning of the expression is to include a variation of ±10% from the specific quantity in some embodiments.

[0097] The directional terms mentioned in the present invention, such as "center", "horizontal", "vertical", "top", "bottom", "up", "down", "front", "back", "left", "right", "inside", "outside", etc., indicate the orientation or position relationship only based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. Moreover, throughout the drawings, the same elements are represented by the same or similar reference numerals. Moreover, the shapes and sizes of the components in the drawings do not reflect the actual size and proportion, but only illustrate the contents of the embodiments of the present invention.

[0098] Those skilled in the art will understand that, in the claims and description of the present invention, the word "comprising" does not exclude the presence of elements (or steps) not listed in the claims. The word "a" or "an" preceding an element (or step) does not exclude the presence of a plurality of such elements (or steps).

[0099] Furthermore, the above embodiments are provided solely to enable the present invention to satisfy legal requirements. The present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0100] Similarly, it should be understood that in order to streamline the present invention, in the above description of the exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, the method of the invention should not be interpreted as reflecting the intention that the claimed invention requires more features than those explicitly stated in each claim. More precisely, as reflected in the claims, each inventive aspect consists in less than all the features of the preceding single embodiment. Moreover, the embodiments can be mixed and matched with each other or with other embodiments based on design and reliability considerations, that is, the technical features in different embodiments can be freely combined to form more embodiments. Therefore, the claims following the specific embodiment are hereby expressly incorporated into the specific embodiment, with each claim itself serving as a separate embodiment of the present invention.

[0101] The above specific embodiments provide a detailed description of the objectives, technical means and beneficial effects of the present invention. It should be understood that the purpose of the detailed description is to enable those skilled in the art to understand the present invention more clearly, and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A sound absorption coefficient measuring device, characterized in that: include: Independent sound source cavity and reverberation cavity; The composite acoustic coupling channel is connected between the sound source cavity and the reverberation cavity, and includes: The tapered section has a radial dimension of a longitudinal section that gradually decreases starting from the sound source cavity. The stable configuration section has a radial dimension of a longitudinal section that is constant from the end of the tapered configuration section to the inside of the reverberation cavity; Wherein, the tapered configuration section and the stable configuration section are both arranged around a common linear central axis.

2. The sound absorption coefficient measuring device according to claim 1, characterized in that: A rectangular chamber is formed inside the reverberation cavity, and the dimensions of the three dimensions of the rectangular chamber are between 5 cm and 50 cm; The sound source cavity and the reverberation cavity are both made of materials with a sound reflection coefficient higher than 94%, and the wall thickness of both is greater than 10 mm. The adjacent walls of the two are formed into a rigid integrated structure through a seamless bonding process.

3. The sound absorption coefficient measuring device according to claim 2, characterized in that: The dimensions of the rectangular chamber are between 6 cm and 12 cm in three dimensions; And / or, the sound source cavity and the reverberation cavity are both constructed of polymethyl methacrylate sheets, and the wall thickness of the polymethyl methacrylate sheets is between 15 mm and 25 mm; And / or, the tapered configuration section is formed in the corresponding wall surfaces of the sound source cavity and the reverberation cavity; the stable configuration section is formed in the corresponding wall surface of the reverberation cavity, and the starting end of the stable configuration section is connected to the end of the tapered configuration section; And / or, the end of the stable configuration segment is located at a corner of a wall formed by the shortest side and the longest side in the rectangular chamber, away from the acoustic sensor; And / or, N hemispherical scatterers are fixed to the bottom and side surfaces of the reverberation cavity, where N is greater than or equal to 3.

4. The sound absorption coefficient measuring device according to claim 1, characterized in that: A rectangular chamber is formed inside the reverberation cavity; The size ratios of the three dimensions of the rectangular chamber satisfy The sound absorption surface of the rectangular chamber and the cutoff frequency satisfy the following conditions: Where A is the total sound absorption, n is the number of types of sound-absorbing surfaces with different sound absorption coefficients, S i The sound absorption coefficient is α i is the area of ​​the sound-absorbing surface, and V is the total volume of the rectangular chamber.

5. The sound absorption coefficient measuring device according to claim 1, characterized in that: The tapered configuration section is a truncated cone section, with its tip facing the stable configuration section; The stable configuration section is a cylindrical section; The central axis is perpendicular to the wall surface where the beginning of the frustum section in the sound source cavity is located and the wall surface where the end of the cylindrical section in the reverberation cavity is located.

6. The sound absorption coefficient measuring device according to claim 5, characterized in that: The reverberation cavity is filled with an inert atmosphere; The radius d / 2 of the cylindrical segment satisfies the acoustic cutoff frequency constraint: Where c is the sound velocity of the inert gas in the reverberation cavity under the experimental environment, f max The upper limit frequency of the applicable frequency band of the reverberation room; The composite acoustic coupling channel satisfies: 4.5≤l≤5.5, Wherein, l is the length of the cylindrical segment, d is the diameter of the longitudinal section at the end of the truncated cone segment, which is equal to the diameter of the longitudinal section of the cylindrical segment; d' is the diameter of the longitudinal section at the beginning of the truncated cone segment.

7. The sound absorption coefficient measuring device according to claim 1, characterized in that: The reverberation chamber comprises: The reverberation chamber body is in an upward-opening shape; The reverberation chamber sealing cover is detachably mounted on the opening side of the reverberation chamber body and is locked to the reverberation chamber body by a buckle, with an elastic sealing ring provided at the contact portion between the two; And / or, the sound source cavity includes: The sound source cavity body is in a shape with a side opening; The sound source cavity sealing cover is detachably covered on the opening side of the sound source cavity body and is locked with the sound source cavity body by a snap, and an elastic sealing ring is provided at the contact portion between the two.

8. The sound absorption coefficient measuring device according to claim 7, characterized in that: The measurement frequency is at the ultrasonic frequency; The reverberation cavity is filled with an inert gas atmosphere; The reverberation chamber sealing cover is provided with two air valve mounting holes; The sound absorption coefficient measuring device further comprises: an atmosphere forming component; the atmosphere forming component comprises: An inert gas source with its own first barometer; an air inlet valve, installed in the first air valve mounting hole, with its air inlet end connected to the inert gas source and its air outlet connected to the interior of the reverberation chamber; An air outlet valve is installed in the second air valve installation hole, with its air inlet connected to the interior of the reverberation chamber and its air outlet connected to the atmosphere or an exhaust gas collection container; The second barometer is connected to the reverberation cavity.

9. The sound absorption coefficient measuring device according to claim 7, characterized in that: At least one acoustic sensor cable hole is formed on the reverberation chamber sealing cover; the front end of the acoustic sensor cable is connected to the acoustic sensor in the reverberation chamber, and the rear end is led out from the acoustic sensor cable hole; The sound absorption coefficient measuring device further includes: a bent acoustic sensor bracket, which extends from the acoustic sensor cable hole or a fixed point in the reverberation chamber within the reverberation chamber, and the acoustic sensor is fixed on the top of the bracket, and allows the user to freely bend and shape it according to needs to define the position of the top acoustic sensor; And / or, a sound-generating device is provided in the sound source cavity, and the sound radiating end of the sound-generating device is coaxially aligned with the opening of the tapered configuration section toward the sound source cavity; a sound-generating device cable hole is provided on the sound source cavity sealing cover; the front end of the sound-generating device cable is connected to the sound-generating device, and the tail end is led out from the sound-generating device cable hole.

10. The sound absorption coefficient measuring device according to any one of claims 1 to 9, further comprising: Main control module; The signal transmitting module includes: an ultrasonic player and a sound generating device disposed in the sound source cavity. The signal transmitting module is used to continuously and periodically transmit an excitation signal to the reverberation cavity through the sound generating device according to the instruction of the main control module; The signal acquisition module includes a power amplifier, a data acquisition card, and an acoustic sensor disposed in the reverberation chamber, and is used to upload the feedback signal collected by the acoustic sensor to the main control module; The main control module also includes: Signal processing module, responsible for processing the excitation signal and feedback signal; The result display module includes: a time domain sound pressure waveform display unit, a frequency domain sound pressure spectrum display unit and a frequency domain sound pressure level characteristic curve unit, which are respectively used to generate and display the time domain sound pressure curve waveform, the frequency domain sound pressure spectrum and the frequency domain sound pressure level characteristic curve.

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