Two-dimensional system irregular incidence sound absorption testing device and method

Abstract

The invention discloses a two-dimensional system irregular incidence sound absorption testing device and method, and the device comprises a two-dimensional closed acoustic system, a sound absorption material to be tested, an omnidirectional sound source, a microphone, a power amplifier, a signal receiving and transmitting module, and an upper computer. Sound absorption materials to be tested are uniformly laid on the boundary of the two-dimensional closed acoustic system at equal thickness; the omni-directional sound source can excite pulse sound waves in the 360-degree direction at the same time. The microphone collects an acoustic pulse response signal of the two-dimensional closed acoustic system; the power amplifier amplifies the pulse excitation signal; the signal transceiving module receives a pulse excitation signal from the upper computer, sends the pulse excitation signal to the power amplifier and receives a sound pulse response signal acquired by the microphone; and the upper computer measures and obtains system reverberation time by adopting a pulse reverse integration method according to the sound pulse response signal, and calculates and obtains a two-dimensional irregular incidence sound absorption coefficient of the sound absorption material by utilizing the system reverberation time. According to the invention, the two-dimensional irregular incidence sound absorption coefficient of the sound absorption material can be tested.

Description

Technical Field

[0001] The invention belongs to the field of sound absorption testing, and in particular relates to a two-dimensional system irregular incident sound absorption testing device and method. Background Art

[0002] Sound absorption test is an effective method to evaluate the sound absorption performance of materials. Material sound absorption test generally includes two methods: impedance tube sound absorption test method and reverberation chamber sound absorption test method. The impedance tube sound absorption test method is used to test the normal incidence sound absorption coefficient of the material, and is used to evaluate the normal incidence sound absorption performance of the material. The reverberation chamber sound absorption test method is used to test the three-dimensional random incidence sound absorption coefficient of the material, and is used to evaluate the three-dimensional random incidence sound absorption performance of the material. The impedance tube method is applicable to one-dimensional acoustic systems, and the reverberation chamber method is applicable to three-dimensional acoustic systems. Because the theoretical method of random incidence sound absorption test in three-dimensional systems is not applicable to two-dimensional systems, the random incidence sound absorption test method of two-dimensional systems still needs to be explored. Summary of the invention

[0003] The purpose of the present invention is to provide a two-dimensional system random incidence sound absorption test device and method, which can test and obtain the two-dimensional random incidence sound absorption coefficient of the sound absorbing material.

[0004] In order to achieve the above-mentioned object, one aspect of the present invention provides a two-dimensional system irregular incidence sound absorption test device, comprising a two-dimensional closed acoustic system, a sound absorbing material to be tested, an omnidirectional sound source, a microphone, a power amplifier, a signal transceiver module, and a host computer:

[0005] The two-dimensional closed acoustic system is rectangular, the internal medium is air, and the system boundary is an acoustic hard boundary; the sound-absorbing material to be tested is evenly laid on the boundary of the two-dimensional closed acoustic system with equal thickness; the omnidirectional sound source is placed at the center of the two-dimensional closed acoustic system, and can simultaneously excite pulse sound waves in 360-degree directions; the microphone is arranged in the central area of ​​the system near the omnidirectional sound source, and is used to collect the acoustic pulse response signal of the two-dimensional closed acoustic system; the power amplifier is connected to the omnidirectional sound source, and is used to amplify the pulse excitation signal; the signal transceiver module is connected to the power amplifier, the microphone and the host computer, and is used to receive the pulse excitation signal from the host computer and send it to the power amplifier and receive the acoustic pulse response signal collected by the microphone;

[0006] The host computer is connected to the signal transceiver module, and is used to send a pulse excitation signal to the signal transceiver module, receive an acoustic pulse response signal from the signal transceiver module, and measure the system reverberation time by using a pulse reverse integration method according to the acoustic pulse response signal, and calculate the two-dimensional irregular incident sound absorption coefficient of the sound absorbing material by using the system reverberation time.

[0007] Preferably, the sound absorbing material to be tested includes sponge and fiber.

[0008] Another aspect of the present invention provides a two-dimensional system random incidence sound absorption test method, using the above-mentioned device to test and obtain the two-dimensional random incidence sound absorption coefficient, the method comprising:

[0009] The host computer transmits a pulse excitation signal, which is transmitted to the omnidirectional sound source after passing through the signal transceiver module and the power amplifier. The omnidirectional sound source excites pulse sound waves in a 360-degree direction. The pulse sound waves respond inside the two-dimensional closed acoustic system. The microphone collects the sound pulse response signal, which is transmitted to the host computer after passing through the signal transceiver module.

[0010] The host computer measures the system reverberation time according to the acoustic pulse response signal through the pulse reverse integration method, and calculates the two-dimensional irregular incident sound absorption coefficient according to the system reverberation time.

[0011] Preferably, the two-dimensional random incidence sound absorption coefficient is calculated as follows:

[0012]

[0013] Among them, α d is the two-dimensional random incidence sound absorption coefficient, T 60 is the system reverberation time, S is the system area, S = l x l y , l x , k y are the length and width of the rectangle of the two-dimensional closed acoustic system, L is the boundary length of the rectangle, and c0 is the speed of sound.

[0014] The two-dimensional system random incidence sound absorption testing device and method according to the above aspects of the present invention can test and obtain the two-dimensional random incidence sound absorption coefficient of the sound absorbing material. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings used in the description of the embodiments of the present invention. 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 these drawings without creative work:

[0016] Figure 1 2. It is a schematic structural diagram of a two-dimensional system irregular incidence sound absorption test device according to an embodiment of the present invention;

[0017] Figure 2 is a schematic diagram of a two-dimensional acoustic model according to an embodiment of the present invention;

[0018] Figure 3 It is a schematic diagram of a two-dimensional irregular incident sound absorption coefficient-reverberation time curve according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] One embodiment of the present invention provides a two-dimensional system irregular incident sound absorption test device, such as Figure 1 As shown, the two-dimensional system irregular incidence sound absorption test device of the embodiment of the present invention includes a two-dimensional closed acoustic system 1, a sound absorption material to be tested 2, an omnidirectional sound source 3, a microphone 4, a power amplifier 5, a signal transceiver module 6, and a host computer 7.

[0021] Among them, the two-dimensional closed acoustic system 1 is rectangular, the internal medium is air, and the system boundary is an acoustic hard boundary. The sound-absorbing material 2 to be tested is evenly laid on the boundary of the two-dimensional closed acoustic system 1 with equal thickness, and the sound-absorbing material 2 to be tested includes but is not limited to sponge, fiber and other materials. The omnidirectional sound source 3 is placed at the center of the two-dimensional closed acoustic system 1, and can simultaneously excite sound waves in 360-degree directions to excite sound signals. The microphone 4 is arranged in the central area of ​​the system near the omnidirectional sound source 3, and is used to collect the system sound response signal. The power amplifier 5 is connected to the omnidirectional sound source 3, and is used to amplify the sound excitation signal.

[0022] The signal transceiver module 6 is connected to the power amplifier 5, the microphone 4, and the host computer 7 for transmitting and collecting system signals. The host computer 7 is connected to the signal transceiver module 6 and contains sound absorption test software for acoustic signal excitation, collection and data processing.

[0023] Specifically, the signal transceiver module 6 receives the pulse excitation signal from the host computer 7 and sends it to the power amplifier 5 and receives the acoustic pulse response signal collected by the microphone 4. The host computer 7 sends the pulse excitation signal to the signal transceiver module 6, receives the acoustic pulse response signal from the signal transceiver module 6, and uses the pulse reverse integration method to test the system reverberation time according to the acoustic pulse response signal, and uses the system reverberation time to calculate the two-dimensional irregular incident sound absorption coefficient of the sound absorbing material.

[0024] The embodiment of the present invention also provides a two-dimensional system random incident sound absorption test method, and the two-dimensional system random incident sound absorption test device of the above embodiment is used to test the two-dimensional random incident sound absorption coefficient. When testing the method of the embodiment of the present invention, the sound absorbing material 2 to be tested is evenly laid on the boundary of the two-dimensional closed acoustic system 1 with equal thickness, the omnidirectional sound source 3 is placed in the center of the two-dimensional closed acoustic system 1, and the microphone 4 is arranged in the central area of ​​the system near the omnidirectional sound source 3. Then, the host computer 7 transmits a pulse excitation signal, and the pulse excitation signal is transmitted to the omnidirectional sound source 3 after passing through the signal transceiver module 6 and the power amplifier 5. The omnidirectional sound source 3 excites a pulse sound wave in a 360-degree direction, and the pulse sound wave responds inside the two-dimensional closed acoustic system 1. The microphone 4 collects the sound pulse response signal, and the measured signal is transmitted to the host computer 7 after passing through the signal transceiver module 6. The host computer 7 obtains the reverberation time according to the sound pulse response signal by the pulse reverse integration method, and calculates the two-dimensional random incident sound absorption coefficient according to the reverberation time. The specific calculation process is described below.

[0025] like Figure 2 As shown, assuming that the length and width of the two-dimensional closed acoustic system are l x , l y , whose boundaries are parallel to the coordinate axes x and y respectively. Assume that there is a sound source at the center M of the system that emits a sound line MP, which forms an angle θ with the y-axis. The sound line propagates in a straight line before hitting the wall, and its energy is attenuated after hitting the wall. After mirror reflection, it continues to propagate in a new direction until it hits another wall and then reflects attenuatedly, and continues to propagate in this way. Considering that the speed of the sound line is the speed of sound c0, for any set of parallel walls, the number of collisions per second of the sound line is equal to the component of the speed of sound c0 in the direction perpendicular to the wall divided by the distance between the two walls. The components of the speed of sound c0 in the x and y directions are equal to c0 sinθ and c0 cosθ, so the number of collisions corresponding to the walls perpendicular to the x and y axes is equal to c0sinθ / l x and c0 cosθ / l y Assume that 2πn rays are emitted from the sound source M per second, and n is the number of sound rays emitted within a unit angle. Then the number of transmitted sound rays in the θ direction is equal to dθn, and the total number of sound ray collisions per second is

[0026]

[0027] Where L = 2 (l x +l y ) is the length of the rectangle boundary (perimeter), S = l x l y is the area of ​​the rectangle. Because the total distance traveled by all sound rays within 1s is equal to L t =2πnc0, the mean free path can be obtained by dividing the total distance by the total number of collisions

[0028]

[0029] The mean free path It is only relevant to the system area S and the boundary length L.

[0030] Consider that the sound source excitation makes the system reach a steady state and then suddenly stops. The sound field inside the system is a diffuse sound field, and the energy density inside the system gradually decays. Assuming that the stopping time t = 0, the average energy density inside the system is Without loss of generality, consider the i-th boundary length and two-dimensional random incident sound absorption coefficient of the system to be equal to l i and α i , in t seconds, the number of collisions between the propagation process of the sound line and the i-th boundary is proportional to its length

[0031]

[0032] Within t seconds after the sound source stops, the average energy density of the system is

[0033]

[0034] Considering that the sound-absorbing material is evenly laid at the system boundary with equal thickness, the two-dimensional irregular incident sound absorption coefficient of each boundary of the system is equal to α d , so there is

[0035]

[0036] Since the total average energy density of each point in the system is equal to the superposition of the average energy density of many irrelevant sound rays, and the total average energy density is proportional to the square of the effective sound pressure, the above formula can be rewritten as

[0037]

[0038] where p e is the effective sound pressure of the system at time t, p e0 is the effective sound pressure at time t = 0. According to the reverberation time T 60 The definition of is equal to the time it takes for the sound pressure level of a steady-state reverberation system to drop by 60 dB after the sound source stops emitting sound (equal to the time it takes for the average sound energy density to drop to 10 of its initial value). -6 ), so there is a relationship

[0039]

[0040] The reverberation time is thus obtained

[0041]

[0042] Then the random incidence sound absorption coefficient can be obtained

[0043]

[0044] According to the above relationship, when the system reverberation time T is measured, 60 Then, combining the system area S, perimeter L and sound speed c0, the two-dimensional random incidence sound absorption coefficient α can be obtained d Thus, the theoretical relationship between the reverberation time and the two-dimensional random-incidence sound absorption coefficient in a two-dimensional closed acoustic system is established.

[0045] To verify the above theoretical relationship, a two-dimensional acoustic model was established in the finite element software COMSOL. The reverberation time of the system was calculated by setting the two-dimensional random incident sound absorption coefficient of the boundary, and then the reverberation time calculated by the software was compared with the theoretically predicted reverberation time, where the theoretically predicted reverberation time was calculated by formula (8). The two-dimensional acoustic model was established using the ray acoustics module of the finite element COMSOL. The model length was 10m, the model width was 10m, the model medium was set to air, the air sound velocity was given to be 343m / s, a pulse excitation was applied at the middle position of the model, 30,000 sound rays were released along the 360° direction, and the reverberation time was calculated when the two-dimensional random incident sound absorption coefficient of the boundary was equal to different values.

[0046] Theoretical predictions and simulation results are shown in Figure 3 As shown, the reverberation time decreases with the increase of the two-dimensional random incident sound absorption coefficient, that is, when the two-dimensional random incident sound absorption coefficient of the system boundary is larger, the overall energy of the system decays faster, and the system reverberation time is smaller, which is consistent with the actual situation; when the two-dimensional random incident sound absorption coefficient increases from 0.1 to 0.8, the system reverberation time decreases from 3.1s to 0.2s, and the change trend of the two gradually becomes gentle, and the theoretically predicted reverberation time is basically equal to the simulated reverberation time. The results show that the theoretically predicted reverberation time is basically consistent with the simulated reverberation time, indicating that the established theoretical relationship between the reverberation time and the two-dimensional random incident sound absorption coefficient is valid and can be applied to the two-dimensional random incident sound absorption test, and the two-dimensional system random incident sound absorption test method of the present invention is feasible.

[0047] In summary, according to the two-dimensional system random incidence sound absorption test device and method of the above embodiment of the present invention, the sound absorbing material is evenly laid on the boundary of the two-dimensional closed acoustic system, and the theoretical relationship between the reverberation time and the random incidence coefficient in the two-dimensional acoustic system is established. The pulse reverse integration method is used to measure the reverberation time in the two-dimensional acoustic system, and the two-dimensional random incidence sound absorption coefficient is obtained according to the measured reverberation time. A key method for random incidence sound absorption testing in a two-dimensional system is provided, which solves the problem of testing the random incidence sound absorption coefficient of a two-dimensional system, fills the testing gap of the two-dimensional random incidence sound absorption coefficient in the field of material sound absorption testing, and belongs to a new material sound absorption testing method.

[0048] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A two-dimensional system irregular incidence sound absorption test device, characterized in that: Including two-dimensional closed acoustic system, sound-absorbing material to be tested, omnidirectional sound source, microphone, power amplifier, signal transceiver module, host computer: The two-dimensional closed acoustic system is rectangular, the internal medium is air, and the system boundary is an acoustic hard boundary; the sound-absorbing material to be tested is evenly laid on the boundary of the two-dimensional closed acoustic system with equal thickness; the omnidirectional sound source is placed at the center of the two-dimensional closed acoustic system, and can simultaneously excite pulse sound waves in 360-degree directions; The microphone is arranged in the central area of ​​the system near the omnidirectional sound source, and is used to collect the acoustic pulse response signal of the two-dimensional closed acoustic system; the power amplifier is connected to the omnidirectional sound source, and is used to amplify the pulse excitation signal; the signal transceiver module is connected to the power amplifier, the microphone and the host computer, and is used to receive the pulse excitation signal from the host computer and send it to the power amplifier, and receive the acoustic pulse response signal collected by the microphone; The host computer is connected to the signal transceiver module, and is used to send a pulse excitation signal to the signal transceiver module, receive an acoustic pulse response signal from the signal transceiver module, and measure the system reverberation time by using a pulse reverse integration method according to the acoustic pulse response signal, and calculate the two-dimensional irregular incident sound absorption coefficient of the sound absorbing material by using the system reverberation time.

2. The device according to claim 1, characterized in that The sound absorbing materials to be tested include sponges and fibers.

3. A two-dimensional system irregular incidence sound absorption test method, characterized in that: The two-dimensional random incidence sound absorption coefficient is obtained by testing using the device described in claim 1 or 2, and the method comprises: The host computer transmits a pulse excitation signal, which is transmitted to the omnidirectional sound source after passing through the signal transceiver module and the power amplifier. The omnidirectional sound source excites pulse sound waves in a 360-degree direction. The pulse sound waves respond inside the two-dimensional closed acoustic system. The microphone collects the sound pulse response signal, which is transmitted to the host computer after passing through the signal transceiver module. The host computer measures the system reverberation time according to the acoustic pulse response signal through the pulse reverse integration method, and calculates the two-dimensional irregular incident sound absorption coefficient according to the system reverberation time.

4. The method according to claim 3, characterized in that: The two-dimensional random incidence sound absorption coefficient is calculated as follows: Among them, α d is the two-dimensional random incidence sound absorption coefficient, T 60 is the system reverberation time, S is the system area, S = l x l y , l x , l y are the length and width of the rectangle of the two-dimensional closed acoustic system, L is the boundary length of the rectangle, and c0 is the speed of sound.

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