CN107907595B - Sound absorption coefficient and sound insulation amount measuring device and measuring method for sound wave oblique incidence material - Google Patents
Sound absorption coefficient and sound insulation amount measuring device and measuring method for sound wave oblique incidence material Download PDFInfo
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- CN107907595B CN107907595B CN201711455921.7A CN201711455921A CN107907595B CN 107907595 B CN107907595 B CN 107907595B CN 201711455921 A CN201711455921 A CN 201711455921A CN 107907595 B CN107907595 B CN 107907595B
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Abstract
The invention relates to a device and a method for measuring sound absorption coefficient and sound insulation quantity of an acoustic wave oblique incidence material, and belongs to the field of acoustic measurement. The loudspeaker is connected with the sound transmission pipe, and the other end of the sound transmission pipe is connected with the first opening of the tee pipe fitting; one end of the reflecting pipe is provided with a sound absorption tail end pipe A, and the other end of the reflecting pipe is connected with a second opening of the three-way pipe fitting; the sound transmission pipe and the reflecting pipe are provided with mounting holes, and the microphone is mounted in the mounting holes. The three-way pipe fitting is a reducing three-way pipe fitting or an equal-diameter three-way pipe fitting, the third opening of the reducing three-way pipe fitting is connected with the test piece cylinder, and the third opening of the equal-diameter three-way pipe fitting is connected with one end of the refraction pipe. The advantages are that: the measurement of the sound absorption coefficient and the sound insulation quantity of the material with the frequency from 100Hz to 1600Hz can be realized. The device has small required sample and simple equipment, and can be operated in a common laboratory.
Description
Technical Field
The invention relates to the field of acoustic measurement, in particular to a device and a method for measuring the sound absorption coefficient and sound insulation of an acoustic oblique incidence material.
Background
With the development of modern industry, transportation industry and city construction, environmental noise pollution has become one of the most influencing public hazards. The use of sound absorbing materials and sound insulating materials is a main measure adopted by the passive control technology to control noise, and in terms of acoustics, main parameters for evaluating the acoustic performance of the materials are as follows: sound absorption coefficient and sound insulation. The method for measuring the sound absorption coefficient and the sound insulation in the laboratory mainly comprises the following steps: reverberant room method and impedance tube method.
The principle of measuring the sound absorption coefficient of the material by the reverberation room method is that the material is 10-12 m 2 Test pieces of (2) are placed in 200-250 m 3 Measuring the reverberation time and calculating the sound absorption coefficient of the material by using a Sibine formula; the principle of measuring the sound insulation of the material by using the reverberation room method is that two adjacent materials are not smaller than 50m 3 One is used as a sound source chamber, the other is used as a receiving chamber, a test piece is arranged in a public wall surface mounting hole, indoor sound pressure is measured by using a microphone, and finally, the material sound insulation quantity is calculated according to a sound insulation quantity measurement formula of the reverberation chamber.
The method for measuring the sound absorption coefficient of the material by the impedance tube can be divided into: standing wave ratio methods and transfer function methods. The standing-wave ratio method is a traditional method for measuring the sound absorption coefficient of the material by using the impedance tube, and the standing-wave ratio is used for calculating the normal incidence sound absorption coefficient of the material, so that single-frequency measurement can be only carried out, and the efficiency is low. The transfer function method is that after the spectrum analysis theory and the FFT algorithm are mature gradually, the modern spectrum analysis method is utilized, the sound absorption coefficient of the material is measured by utilizing the transfer function of the impedance tube double microphones, the sound absorption coefficient of each frequency in the working frequency band of the impedance tube can be obtained by one-time measurement, and the efficiency is high.
The method for measuring the sound insulation of the material by the impedance tube can be divided into: the four microphone method and the dual load method. The four-microphone method is a method for improving and measuring the sound insulation quantity of a material by using an impedance tube based on the previous three-microphone measuring method, and obtaining the normal incidence sound insulation quantity of the material by using a standing wave separation method and using a transmission coefficient. The dual load method is a method of compensating for the non-ideal sound absorption end of the four microphone method by performing two measurements under two different boundary conditions.
At present, the sound absorption coefficient and sound insulation amount measuring equipment of sound absorption and sound insulation materials are designed based on the method, the area of a test piece required by a reverberation room method is large, the construction cost is high, and the method is not suitable for being used as a reference measuring method for experimental study. The impedance tube method can only measure the sound absorption coefficient and the sound insulation amount of the material when the sound wave is vertically incident. However, some materials, such as glass wool and rock wool, have great differences between the sound absorption coefficient of the material when sound waves are obliquely incident and the sound absorption coefficient when sound waves are perpendicularly incident, so the sound absorption coefficient of the material is also an important basis for judging the performance of the material in engineering, and therefore the measurement of the sound absorption coefficient of the sound wave obliquely incident material has important significance, but no suitable method and measuring device for specially measuring the sound absorption performance of the sound wave obliquely incident material exist at present.
Disclosure of Invention
The invention aims to provide a device and a method for measuring the sound absorption coefficient and the sound insulation amount of an acoustic wave oblique incidence material, which solve the problems that an impedance tube in the prior art can only measure the sound absorption coefficient and the sound insulation amount of the material when acoustic waves are perpendicularly incident. The invention combines the advantages of the reverberation chamber and the impedance tube by utilizing the acoustic wave refraction and reflection principle and the in-tube plane wave theory.
The above object of the present invention is achieved by the following technical solutions:
the device for measuring the sound absorption coefficient and the sound insulation quantity of the sound wave oblique incidence material is characterized in that: the loudspeaker 1 is connected with one end of the sound transmission tube 3, and the other end of the sound transmission tube 3 is connected with a first opening of the tee pipe fitting 4; one end of the reflecting pipe 7 is provided with a sound absorption tail end pipe A8, and the other end of the reflecting pipe is connected with a second opening of the three-way pipe fitting 4; the sound absorption tail end pipe A8 is filled with sound absorption materials to enable the tail end of the reflecting pipe 7 to reflect silent waves; three mounting holes 6 are formed in the sound transmission tube 3, microphones are mounted in two mounting holes 6, the front ends of the microphones are leveled with the inner wall of the impedance tube, namely the sound transmission tube 3, and the other mounting hole 6 is temporarily sealed through a push rod made of metal so as to prevent sound leakage; three mounting holes 6 are formed in the reflecting tube 7, microphones are mounted in two mounting holes 6, the front ends of the microphones are leveled with the inner wall of the impedance tube-the reflecting tube 7, and the other mounting hole 6 is temporarily sealed through a push rod made of metal to prevent sound leakage.
The included angle between the sound transmission tube 3 and the reflecting tube 7 is 30-75 degrees.
The three-way pipe fitting 4 is a reducing three-way pipe fitting, the test piece 5 is placed in the reducing three-way pipe fitting, a third opening of the reducing three-way pipe fitting is connected with the test piece barrel 10, a piston rod 11 is arranged in the center of the test piece barrel 10 and goes deep into the reducing three-way pipe fitting, a back plate 9 is arranged at one end of the piston rod 11 extending into the reducing three-way pipe fitting, a cavity is formed between the back plate 9 and the test piece 5, and the size of the cavity is regulated through the piston rod 11; the structure is supported by a base 2 to form a sound wave oblique incidence material sound absorption coefficient measuring device; when the included angle between the sound transmission tube 3 and the reflecting tube 7 is 30 degrees, 45 degrees, 60 degrees and 75 degrees, the cross sections of the first opening and the second opening of the reducing tee pipe fitting are equal-diameter circles, the cross section of the third opening is an ellipse with the same short axis and different long axes.
The three-way pipe fitting 4 is an equal-diameter three-way pipe fitting, the test piece 5 is placed in the equal-diameter three-way pipe fitting, a third opening of the equal-diameter three-way pipe fitting is connected with one end of the refraction pipe 12, the other end of the refraction pipe 12 is provided with a sound absorption tail end pipe B13, and sound absorption materials are filled in the sound absorption tail end pipe B13 to enable silent waves at the tail end of the refraction pipe 12 to be reflected; two mounting holes 6 are formed in the refraction tube 12, microphones are respectively mounted in the two mounting holes 6, and the front ends of the microphones are level with the inner wall of the impedance tube-the refraction tube 12; the structure is supported by a base 2 to form an acoustic wave oblique incidence material sound insulation measuring device; when the included angle between the sound transmission tube 3 and the reflecting tube 7 is 30 degrees, 45 degrees, 60 degrees and 75 degrees, the cross sections of the first opening, the second opening and the third opening of the equal-diameter three-way pipe fitting are equal-diameter circles.
The measuring method of the sound absorption coefficient measuring device of the sound wave oblique incidence material comprises the following steps:
1) The signal generator enables the loudspeaker to emit Gaussian white noise into the sound wave oblique incidence material sound absorption coefficient measuring device through the power amplifier;
2) The four-channel data acquisition card is connected with the microphone through the signal conditioner, and respectively acquires sound pressure signals at the position of the microphone and transmits the sound pressure signals to the computer;
3) And the computer respectively calculates the reflection coefficient of the material and the change curve of the sound absorption coefficient along with the frequency under the incidence angles of sound waves after the four reducing tee pipe fittings are placed in the test piece by utilizing a sound absorption coefficient calculation formula.
The calculation process of the reflection coefficient and the sound absorption coefficient is as follows:
1) The near-end microphone on the sound transmission tube, namely the microphone closest to the test piece on the sound transmission tube, and the collected sound pressure is p 2 The far-end microphone on the sound transmission tube, namely the microphone on the sound transmission tube farthest from the test piece, and the collected sound pressure is p 1 Will p 2 And p is as follows 1 The quotient is obtained to obtain the incident wave transfer function H 1 ；
2) Collecting sound pressure p of a near-end microphone on the reflecting tube, namely a microphone closest to the test piece on the reflecting tube 3 The collected sound pressure is p with the far-end microphone on the reflecting tube, namely the microphone on the reflecting tube farthest from the test piece 4 Will p 3 And p is as follows 4 The quotient is obtained to obtain the reflected wave transfer function H 2 ；
3) The sound pressure summation of the incident wave and the reflected wave collected by the remote microphones of the sound transmission pipe and the reflecting pipe is P 1 The sound pressure of the incident wave and the sound pressure of the reflected wave collected by the near-end microphones of the sound transmission pipe and the reflecting pipe are summed to be P 2 Will P 2 And P 1 The quotient is obtained that the transfer function of the total sound field in the sound absorption coefficient measuring device is H 12 ；
4) By utilizing the relation between the transfer function of the total sound field in the sound absorption coefficient measuring device and the transfer function of the incident wave and the transfer function of the reflected wave, the reflection coefficient r can be deduced and calculated according to the following formula:
wherein H is 1 To be the transfer function of the incident wave, H 2 For the reflected wave transfer function H 12 As a transfer function of the total sound field in the sound absorption coefficient measuring device, x 1 The distance between the test piece on the sound transmission tube and the reflecting tube and the far-end microphone is the distance between the sound transmission tube and the microphone on the reflecting tube, which is farthest from the test piece;
the sound absorption coefficient α is calculated according to the following formula: α=1- |r| 2 。
The measuring method of the sound insulation amount measuring device for the sound wave oblique incidence material comprises the following steps:
1) The signal generator enables the loudspeaker to emit Gaussian white noise into the sound insulation amount measuring device of the sound wave oblique incidence material through the power amplifier;
2) The six-channel data acquisition card is connected with the microphone through the signal conditioner, and respectively acquires sound pressure signals at the position of the microphone and transmits the sound pressure signals to the computer;
3) The computer calculates the transmission coefficient of the material under each angle of incidence of sound waves after the four equal-diameter tee pipe fittings are placed in the test piece by using the sound insulation amount calculation formula, and the change curve of the sound insulation amount along with the frequency.
The transmission coefficient and the sound insulation are calculated as follows: transmission coefficient t p Calculated according to the following formula:
the sound insulation TL is calculated according to the following formula: tl= -20lgt p |
Wherein x is 1 For the distance x between the test piece on the sound transmission tube and the reflecting tube and the far-end microphone, namely the distance x between the sound transmission tube and the microphone on the reflecting tube furthest from the test piece 2 For the distance x between the test piece on the sound transmission tube and the reflecting tube and the near-end microphone, namely the microphone on the sound transmission tube and the reflecting tube closest to the test piece 3 X is the distance between the test piece on the refraction tube and the near-end microphone 4 P is the distance between the test piece on the refraction tube and the far-end microphone 1 For distance toTest piece x 1 Sound pressure sum, P collected by two microphones at a location 2 To be away from the test piece x 2 Sound pressure sum, P collected by two microphones at a location 3 To be away from the test piece x 3 Sound pressure, P, collected by microphones at locations 4 To be away from the test piece x 4 The sound pressure picked up by the microphone at the location,
for the amplitude of the complex sound pressure of the incident wave, < >>
The amplitude of the complex sound pressure of the transmission wave, k is the complex wave number of the sound wave, s is the distance between the sound transmission tube, the reflecting tube and the two microphones on the transmission tube, and t p TL is the sound insulation amount, which is the transmission coefficient.
The invention has the beneficial effects that: the device for measuring the sound absorption coefficient and the sound insulation amount of the sound wave oblique incidence material actually changes the angle of the sound wave incidence material by changing the reducing tee pipe fitting and the equal-diameter tee pipe fitting, and the device can measure the change curve of the sound absorption coefficient and the sound insulation amount of the sound wave incidence angle 30 degrees, 45 degrees, 60 degrees and 75 degrees of material along with the frequency. During testing, the tested frequency range is adjusted by utilizing the difference of the distances between the two microphones, and the measurement of the sound absorption coefficient and the sound insulation quantity of the material with the frequency from 100Hz to 1600Hz can be realized. The device has small required sample and simple equipment, and can be operated in a common laboratory. Therefore, the device for measuring the sound absorption coefficient and the sound insulation amount of the sound wave oblique incidence material has the advantages of portability, easiness in operation, simplicity in measuring method, economy and convenience, capability of measuring the change of the sound absorption coefficient and the sound insulation amount of the material when the sound wave is obliquely incident in a larger frequency band, and the like. These excellent properties can greatly improve the current technology. The novel advantages are presented in the aspects of sound absorption coefficient, reflection coefficient, impedance and admittance measurement and the like when sound waves are obliquely incident to the material.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate and explain the invention and together with the description serve to explain the invention.
FIG. 1 is a schematic diagram of a sound absorption coefficient measuring device for sound wave oblique incidence materials;
FIG. 2 is a schematic diagram of the structure of the sound insulation measuring device of the sound wave oblique incidence material;
FIG. 3 is a schematic view of the structure of the reducing tee pipe fitting (the included angle between the sound transmission pipe and the reflection pipe is 30 degrees, 60 degrees and 75 degrees) and the test piece cylinder;
fig. 4 is a schematic structural view of the equal-diameter three-way pipe fitting (the included angle between the sound transmission pipe and the reflection pipe is 30 °, 60 °, 75 °);
FIG. 5 is a block diagram of a circuit of the acoustic absorption coefficient measuring device of the acoustic oblique incidence material of the present invention;
fig. 6 is a circuit block diagram of the sound insulation amount measuring device of the sound wave oblique incidence material.
In the figure: 1. a speaker; 2. a base; 3. a sound transmission tube; 4. a three-way pipe fitting; 5. a test piece; 6. a mounting hole; 7. a reflection tube; 8. a sound absorbing end pipe a; 9. a back plate; 10. a test piece cylinder; 11. a piston rod; 12. a refractive tube; 13. and a sound absorbing end pipe B.
Detailed Description
The details of the present invention and its specific embodiments are further described below with reference to the accompanying drawings.
Referring to fig. 1 to 4, the sound absorption coefficient and sound insulation amount measuring device of the sound wave oblique incidence material of the invention is characterized in that a loudspeaker 1 is connected with one end of a sound transmission tube 3, and the other end of the sound transmission tube 3 is connected with a first opening of a tee pipe fitting 4; one end of the reflecting pipe 7 is provided with a sound absorption tail end pipe A8, and the other end of the reflecting pipe is connected with a second opening of the three-way pipe fitting 4; the sound absorption tail end pipe A8 is filled with sound absorption materials to enable the tail end of the reflecting pipe 7 to reflect silent waves; three mounting holes 6 are formed in the sound transmission tube 3, microphones are mounted in two mounting holes 6, the front ends of the microphones are leveled with the inner wall of the impedance tube, namely the sound transmission tube 3, and the other mounting hole 6 is temporarily sealed through a push rod made of metal so as to prevent sound leakage; three mounting holes 6 are formed in the reflecting tube 7, microphones are mounted in two mounting holes 6, the front ends of the microphones are leveled with the inner wall of the impedance tube-the reflecting tube 7, and the other mounting hole 6 is temporarily sealed through a push rod made of metal to prevent sound leakage.
The included angle between the sound transmission tube 3 and the reflecting tube 7 is 30-75 degrees.
The three-way pipe fitting 4 is a reducing three-way pipe fitting, the test piece 5 is placed in the reducing three-way pipe fitting, a third opening of the reducing three-way pipe fitting is connected with the test piece cylinder 10, the cross section of the test piece cylinder is the same as that of the reducing three-way pipe fitting, a piston rod 11 is arranged in the center of the test piece cylinder 10 and goes deep into the reducing three-way pipe fitting, a back plate 9 is arranged at one end of the piston rod 11 extending into the reducing three-way pipe fitting, a cavity is formed between the back plate 9 and the test piece 5, the size of the cavity is regulated by the piston rod 11, and the other end of the piston rod is carved with scales to record the distance from a sample to the surface of the back plate; the structure is supported by the base 2 to form the sound wave oblique incidence material sound absorption coefficient measuring device. During testing, the frequency range of the test is adjusted by utilizing the difference of the distances between the two microphones, so that the measurement of the sound absorption coefficient of the material with the frequency ranging from 100Hz to 1600Hz is realized.
When the included angle between the sound transmission tube 3 and the reflecting tube 7 is 30 degrees, 45 degrees, 60 degrees and 75 degrees, the cross sections of the first opening and the second opening of the reducing tee pipe fitting are equal-diameter circles, the cross section of the third opening is an ellipse with the same short axis and different long axes.
The three-way pipe fitting 4 is an equal-diameter three-way pipe fitting, the test piece 5 is placed in the equal-diameter three-way pipe fitting, a third opening of the equal-diameter three-way pipe fitting is connected with one end of the refraction pipe 12, the other end of the refraction pipe 12 is provided with a sound absorption tail end pipe B13, and sound absorption materials are filled in the sound absorption tail end pipe B13 to enable silent waves at the tail end of the refraction pipe 12 to be reflected; two mounting holes 6 are formed in the refraction tube 12, microphones are respectively mounted in the two mounting holes 6, and the front ends of the microphones are level with the inner wall of the impedance tube-the refraction tube 12; the structure is supported by the base 2 to form the sound insulation amount measuring device of the sound wave oblique incidence material. During testing, the frequency range of the test is adjusted by utilizing the difference of the distances between the two microphones, so that the measurement of the sound insulation quantity of the material with the frequency ranging from 100Hz to 1600Hz is realized.
When the included angle between the sound transmission tube 3 and the reflecting tube 7 is 30 degrees, 45 degrees, 60 degrees and 75 degrees, the cross sections of the first opening, the second opening and the third opening of the equal-diameter three-way pipe fitting are equal-diameter circles.
The measuring method of the sound absorption coefficient measuring device of the sound wave oblique incidence material comprises the following steps:
1) The signal generator enables the loudspeaker to emit Gaussian white noise into the sound wave oblique incidence material sound absorption coefficient measuring device through the power amplifier;
2) The four-channel data acquisition card is connected with the microphone through the signal conditioner, and respectively acquires sound pressure signals at the positions of the microphone in the impedance tube provided with the four reducing tee pipe fittings and transmits the sound pressure signals to the computer;
3) And the computer respectively calculates the reflection coefficient of the material and the change curve of the sound absorption coefficient along with the frequency under the incidence angles of sound waves after the four reducing tee pipe fittings are placed in the test piece by utilizing a sound absorption coefficient calculation formula.
The calculation process of the reflection coefficient and the sound absorption coefficient is as follows:
1) The near-end microphone on the sound transmission tube, namely the microphone closest to the test piece on the sound transmission tube, and the collected sound pressure is p 2 The far-end microphone on the sound transmission tube, namely the microphone on the sound transmission tube farthest from the test piece, and the collected sound pressure is p 1 Will p 2 And p is as follows 1 The quotient is obtained to obtain the incident wave transfer function H 1 ；
2) Collecting sound pressure p of a near-end microphone on the reflecting tube, namely a microphone closest to the test piece on the reflecting tube 3 The collected sound pressure is p with the far-end microphone on the reflecting tube, namely the microphone on the reflecting tube farthest from the test piece 4 Will p 3 And p is as follows 4 The quotient is obtained to obtain the reflected wave transfer function H 2 ；
3) The sound pressure summation of the incident wave and the reflected wave collected by the remote microphones of the sound transmission pipe and the reflecting pipe is P 1 The sound pressure of the incident wave and the sound pressure of the reflected wave collected by the near-end microphones of the sound transmission pipe and the reflecting pipe are summed to be P 2 Will P 2 And P 1 The quotient is obtained that the transfer function of the total sound field in the sound absorption coefficient measuring device is H 12 ；
4) Using transfer function and incident wave transfer function and reflection of total sound field in sound absorption coefficient measuring deviceThe wave transfer function relationship can be deduced that the reflection coefficient r is calculated according to the following formula:
wherein H is 1 To be the transfer function of the incident wave, H 2 For the reflected wave transfer function H 12 As a transfer function of the total sound field in the sound absorption coefficient measuring device, x 1 The distance between the test piece on the sound transmission tube and the reflecting tube and the far-end microphone is the distance between the sound transmission tube and the microphone on the reflecting tube, which is farthest from the test piece;
the sound absorption coefficient α is calculated according to the following formula: α=1- |r| 2 。
The measuring method of the sound insulation amount measuring device for the sound wave oblique incidence material comprises the following steps:
1) The signal generator enables the loudspeaker to emit Gaussian white noise into the sound insulation amount measuring device of the sound wave oblique incidence material through the power amplifier;
2) The six-channel data acquisition card is connected with the microphone through the signal conditioner, respectively acquires sound pressure signals at the positions of the microphone in the impedance tube provided with the four equal-diameter tee pipe fittings, and transmits the sound pressure signals to the computer;
3) The computer calculates the transmission coefficient of the material under each angle of incidence of sound waves after the four equal-diameter tee pipe fittings are placed in the test piece by using the sound insulation amount calculation formula, and the change curve of the sound insulation amount along with the frequency.
The transmission coefficient and the sound insulation are calculated as follows: transmission coefficient t p Calculated according to the following formula:
the sound insulation TL is calculated according to the following formula: tl= -20lg|t p |
Wherein x is 1 For the distance x between the test piece on the sound transmission tube and the reflecting tube and the far-end microphone, namely the distance x between the sound transmission tube and the microphone on the reflecting tube furthest from the test piece 2 The distance between the test piece and the near-end microphone on the sound transmission tube and the reflecting tube, namely the distance between the sound transmission tube and the microphone on the reflecting tube closest to the test piece，x 3 X is the distance between the test piece on the refraction tube and the near-end microphone 4 P is the distance between the test piece on the refraction tube and the far-end microphone 1 To be away from the test piece x 1 Sound pressure sum, P collected by two microphones at a location 2 To be away from the test piece x 2 Sound pressure sum, P collected by two microphones at a location 3 To be away from the test piece x 3 Sound pressure, P, collected by microphones at locations 4 To be away from the test piece x 4 The sound pressure picked up by the microphone at the location,
for the amplitude of the complex sound pressure of the incident wave, < >>
The amplitude of the complex sound pressure of the transmission wave, k is the complex wave number of the sound wave, s is the distance between the sound transmission tube, the reflecting tube and the two microphones on the transmission tube, and t p TL is the sound insulation amount, which is the transmission coefficient.
Examples:
the measuring method of the sound absorption coefficient measuring device of the sound wave oblique incidence material comprises the following steps:
1) Preparation work before measurement:
placing a test piece in the center of a reducing tee pipe fitting, according to the sound wave reflection principle, the distance from the test piece to a near-end microphone on a sound transmission pipe (a microphone closest to the test piece on the sound transmission pipe) is the same as the distance from the test piece to a near-end microphone on a reflecting pipe (a microphone closest to the test piece on the reflecting pipe), the distances between the sound transmission pipe and the three microphones of the reflecting pipe are the same, in order to avoid errors caused by distortion of a sound field on the surface of the test piece, the distance from the test piece to the near-end microphone (the microphone closest to the test piece on the sound transmission pipe and the reflecting pipe) is more than twice the pipe diameter, and according to the influence of humidity, temperature or the internal structure of the microphone, the impedance pipe of the sound wave oblique incidence material sound absorption coefficient measuring device is installed, and the microphone is calibrated by using a calibrator before use; according to the figure 5, the loudspeaker is connected with the computer through the amplifier and the signal generator, the four microphones are respectively connected with the signal conditioners, the signal conditioners are respectively connected with the data acquisition card, and the data acquisition card is connected with the computer; the signal generator is turned on to drive the loudspeaker to sound through the amplifier, plane waves are generated in the impedance tube, and the loudspeaker can generate high-order waves, so that the plane waves are transmitted in the tube, the distance from the surface of the loudspeaker to a far-end microphone (the microphone furthest from a test piece on the sound transmission tube) is more than three times of the tube diameter, and the working performance of the loudspeaker tends to be stable when the loudspeaker works for more than 10 minutes, and the preparation work is marked;
2) Measuring the sound absorption coefficient of the sound wave oblique incidence material:
2.1 Collecting sound pressure signals at the corresponding positions of the microphones by using a four-channel data acquisition card;
2.2 Sound pressure collected by a near-end microphone (a microphone closest to a test piece on the sound transmission tube) on the sound transmission tube is p 2 The sound pressure collected by the far-end microphone on the sound transmission tube (the microphone furthest from the test piece on the sound transmission tube) is p 1 Will p 2 And p is as follows 1 The quotient is obtained to obtain the incident wave transfer function H 1 ；
2.3 The sound pressure collected by the near-end microphone on the reflecting tube (the microphone closest to the test piece on the reflecting tube) is p 3 The sound pressure collected by the far-end microphone on the reflecting tube (the microphone furthest from the test piece on the reflecting tube) is p 4 Will p 3 And p is as follows 4 The quotient is obtained to obtain the reflected wave transfer function H 2 ；
2.4 Sound pressure summation of incident wave and reflected wave collected by the far-end microphone on the sound transmission tube and the reflecting tube is P 1 The sound pressure of the incident wave and the sound pressure of the reflected wave collected by the near-end microphone on the sound transmission tube and the reflecting tube are summed to be P 2 Will P 2 And P 1 The quotient is obtained that the transfer function of the total sound field in the sound absorption coefficient measuring device is H 12 ；
2.5 Using the transfer function of the total sound field in the sound absorption coefficient measuring device, the transfer function of the incident wave and the transfer function of the reflected wave, the reflection coefficient r can be deduced and calculated according to the following formula:
wherein H is 1 To be the transfer function of the incident wave, H 2 For the reflected wave transfer function H 12 As a transfer function of the total sound field in the sound absorption coefficient measuring device, x 1 The distance between the test piece on the sound transmission tube and the reflecting tube and the far-end microphone (the microphone on the sound transmission tube and the reflecting tube farthest from the test piece); according to the formula α=1- |r| 2 The sound absorption coefficient of the material can be obtained when the sound wave obliquely enters;
2.6 The reducing tee pipe fitting and the test piece cylinder in the figure 3 are replaced into the oblique incidence material sound absorption coefficient measuring device, the step 2 is repeated, and finally, the change curve of the sound absorption coefficient of the material with the sound wave incidence angle of 30 degrees, 45 degrees, 60 degrees and 75 degrees along with the frequency can be intuitively seen through numerical calculation.
The measuring method of the sound insulation amount measuring device for the sound wave oblique incidence material comprises the following steps:
1) Preparation work before measurement:
placing a test piece in the center of a reducing tee pipe fitting, according to the sound wave reflection principle, the distance from the test piece to a near-end microphone on a sound transmission pipe (the microphone closest to the test piece on the sound transmission pipe) is the same as the distance from the test piece to a near-end microphone on a reflecting pipe (the microphone closest to the test piece on the reflecting pipe), the distances between the sound transmission pipe and the three microphones of the reflecting pipe are the same, in order to avoid error caused by distortion of a sound field on the surface of a sample, the distance from the test piece to the near-end microphone (the microphone closest to the test piece on the sound transmission pipe and the reflecting pipe) is more than twice the pipe diameter, the distance from the test piece to the near-end microphone (the microphone closest to the test piece on the reflecting pipe) is more than three times the pipe diameter, and according to the method shown in fig. 1, installing an impedance pipe of a sound wave oblique incidence material sound absorption coefficient measuring device, and calibrating the microphone by using a calibrator before use due to the influence of humidity, temperature or the internal structure of the microphone; according to the figure 5, the loudspeaker is connected with the computer through the amplifier and the signal generator, the four microphones are respectively connected with the signal conditioners, the signal conditioners are respectively connected with the data acquisition card, and the data acquisition card is connected with the computer; the invention opens the signal generator and drives the loudspeaker to sound through the amplifier, produces plane wave in the impedance tube, the loudspeaker will produce the high-order wave of course too, therefore the invention is in order to guarantee the intraductal propagation of plane wave, the distance of loudspeaker surface to the far-end microphone (the microphone furthest from test piece on the sound transmission tube) is greater than three pipe diameters, the loudspeaker works for more than 10 minutes, its working performance tends to be stable, mark that the preparation work is finished.
2) Measuring the sound insulation amount of the sound wave oblique incidence material:
2.1 Collecting sound pressure signals at corresponding positions of all microphones in the impedance tube by using a six-channel data acquisition card;
2.2 Using a formula
The transmission coefficient of the material can be obtained when the sound wave is obliquely incident, wherein x is 1 For the distance x between the test piece on the sound transmission tube and the reflecting tube and the far-end microphone, namely the distance x between the sound transmission tube and the microphone on the reflecting tube furthest from the test piece 2 For the distance x between the test piece on the sound transmission tube and the reflecting tube and the near-end microphone, namely the microphone on the sound transmission tube and the reflecting tube closest to the test piece 3 X is the distance between the test piece on the refraction tube and the near-end microphone 4 P is the distance between the test piece on the refraction tube and the far-end microphone 1 To be away from the test piece x 1 Sound pressure sum, P collected by two microphones at a location 2 To be away from the test piece x 2 Sound pressure sum, P collected by two microphones at a location 3 To be away from the test piece x 3 Sound pressure, P, collected by microphones at locations 4 To be away from the test piece x 4 The sound pressure picked up by the microphone at the location,
for the amplitude of the complex sound pressure of the incident wave, < >>
The amplitude of the complex sound pressure of the transmission wave, k is the complex wave number of the sound wave, s is the distance between the sound transmission tube, the reflecting tube and the two microphones on the transmission tube, and t p TL is the sound insulation amount, which is the transmission coefficient.
2.3 The equal-diameter three-way pipe fitting in fig. 4 is replaced into the oblique incidence material sound insulation amount measuring device, the step 2 is repeated, and finally, the change curve of the sound insulation amount of the material with the sound wave incidence angle of 30 degrees, 45 degrees, 60 degrees and 75 degrees along with the frequency can be intuitively seen through numerical calculation.
The above description is only a preferred example of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. The utility model provides a sound wave oblique incidence material sound absorption coefficient and sound proof volume measuring device which characterized in that: the loudspeaker (1) is connected with one end of the sound transmission pipe (3), and the other end of the sound transmission pipe (3) is connected with the first opening of the three-way pipe fitting (4); one end of the reflecting pipe (7) is provided with a sound absorption tail end pipe A (8), and the other end of the reflecting pipe is connected with a second opening of the three-way pipe fitting (4); the sound absorption tail end pipe A (8) is filled with sound absorption materials to enable silent waves at the tail end of the reflecting pipe (7) to be reflected; three mounting holes (6) are formed in the sound transmission tube (3), microphones are mounted in the two mounting holes (6), the front ends of the microphones are level with the inner wall of the impedance tube, namely the sound transmission tube (3), and the other mounting hole (6) is temporarily sealed through a push rod made of metal so as to prevent sound leakage; three mounting holes (6) are formed in the reflecting tube (7), microphones are mounted in the two mounting holes (6), the front ends of the microphones are level with the inner wall of the impedance tube-the reflecting tube (7), and the other mounting hole (6) is temporarily sealed through a push rod made of metal so as to prevent sound leakage; the device for measuring the sound absorption coefficient and the sound insulation amount of the sound wave oblique incidence material actually changes the angle of the sound wave incidence material by changing the reducing tee pipe fitting and the equal-diameter tee pipe fitting, and the device can measure the change curve of the sound absorption coefficient and the sound insulation amount of the sound wave incidence angle of 30 degrees, 45 degrees, 60 degrees and 75 degrees of materials along with the frequency; during testing, the tested frequency range is adjusted by utilizing the difference of the distances between the two microphones, and the measurement of the sound absorption coefficient and the sound insulation quantity of the material with the frequency from 100Hz to 1600Hz can be realized.
2. The sound absorption coefficient and sound insulation amount measuring device of sound wave oblique incidence material according to claim 1, wherein: the included angle between the sound transmission tube (3) and the reflecting tube (7) is 30-75 degrees.
3. The sound absorption coefficient and sound insulation amount measuring device of sound wave oblique incidence material according to claim 1, wherein: the three-way pipe fitting (4) is a reducing three-way pipe fitting, the test piece (5) is placed in the reducing three-way pipe fitting, a third opening of the reducing three-way pipe fitting is connected with the test piece cylinder (10), a piston rod (11) is arranged in the center of the test piece cylinder (10) and goes deep into the reducing three-way pipe fitting, a back plate (9) is arranged at one end, extending into the reducing three-way pipe fitting, of the piston rod (11), a cavity is formed between the back plate (9) and the test piece (5), and the size of the cavity is adjusted through the piston rod (11); the sound transmission pipe (3), the tee pipe fitting (4) and the test piece cylinder (10) are supported by the base (2) to form a sound wave oblique incidence material sound absorption coefficient measuring device; when the included angle between the sound transmission tube (3) and the reflecting tube (7) is 30 degrees, 45 degrees, 60 degrees and 75 degrees, the cross sections of the first opening and the second opening of the reducing tee pipe fitting are equal-diameter circles, the cross section of the third opening is elliptical, the short axis is the same, and the long axes are different.
4. The sound absorption coefficient and sound insulation amount measuring device of sound wave oblique incidence material according to claim 1, wherein: the three-way pipe fitting (4) is a constant diameter three-way pipe fitting, the test piece (5) is placed in the constant diameter three-way pipe fitting, a third opening of the constant diameter three-way pipe fitting is connected with one end of the refraction pipe (12), the other end of the refraction pipe (12) is provided with a sound absorption tail end pipe B (13), and sound absorption materials are filled in the sound absorption tail end pipe B (13) to enable the tail end of the refraction pipe (12) to reflect silent waves; two mounting holes (6) are formed in the refraction tube (12), microphones are respectively mounted in the two mounting holes (6), and the front end of each microphone is level with the inner wall of the impedance tube (12); the three-way pipe fitting (4) and the refracting pipe (12) are supported by the base (2) to form an acoustic wave oblique incidence material sound insulation measuring device; when the included angles between the sound transmission tube (3) and the reflecting tube (7) are 30 degrees, 45 degrees, 60 degrees and 75 degrees, the cross sections of the first opening, the second opening and the third opening of the equal-diameter three-way pipe fitting are equal-diameter circles.
5. The sound absorption coefficient and sound insulation amount measuring device of sound wave oblique incidence material according to claim 3, wherein: the measuring method of the sound absorption coefficient measuring device of the sound wave oblique incidence material comprises the following steps:
1) The signal generator enables the loudspeaker to emit Gaussian white noise into the sound wave oblique incidence material sound absorption coefficient measuring device through the power amplifier;
2) The four-channel data acquisition card is connected with the microphone through the signal conditioner, and respectively acquires sound pressure signals at the position of the microphone and transmits the sound pressure signals to the computer;
3) And the computer respectively calculates the reflection coefficient of the material and the change curve of the sound absorption coefficient along with the frequency under the incidence angles of sound waves after the four reducing tee pipe fittings are placed in the test piece by utilizing a sound absorption coefficient calculation formula.
6. The sound absorption coefficient and sound insulation amount measuring device for sound wave oblique incidence material according to claim 5, wherein: the calculation process of the reflection coefficient and the sound absorption coefficient is as follows:
1) The near-end microphone on the sound transmission tube, namely the microphone closest to the test piece on the sound transmission tube, and the collected sound pressure is p 2 The far-end microphone on the sound transmission tube, namely the microphone on the sound transmission tube farthest from the test piece, and the collected sound pressure is p 1 Will p 2 And p is as follows 1 The quotient is obtained to obtain the incident wave transfer function H 1 ；
2) Collecting sound pressure p of a near-end microphone on the reflecting tube, namely a microphone closest to the test piece on the reflecting tube 3 The collected sound pressure is p with the far-end microphone on the reflecting tube, namely the microphone on the reflecting tube farthest from the test piece 4 Will p 3 And p is as follows 4 The quotient is obtained to obtain the reflected wave transfer function H 2 ；
3) The sound pressure summation of the incident wave and the reflected wave collected by the remote microphones of the sound transmission pipe and the reflecting pipe is P 1 The sound pressure of the incident wave and the sound pressure of the reflected wave collected by the near-end microphones of the sound transmission pipe and the reflecting pipe are summed to be P 2 Will P 2 And P 1 The total sound field in the sound absorption coefficient measuring device is obtained by the manufacturerIs H 12 ；
4) By utilizing the relation between the transfer function of the total sound field in the sound absorption coefficient measuring device and the transfer function of the incident wave and the transfer function of the reflected wave, the reflection coefficient r can be deduced and calculated according to the following formula:
wherein H is 1 To be the transfer function of the incident wave, H 2 For the reflected wave transfer function H 12 As a transfer function of the total sound field in the sound absorption coefficient measuring device, x 1 The distance between the test piece on the sound transmission tube and the reflecting tube and the far-end microphone is the distance between the sound transmission tube and the microphone on the reflecting tube, which is farthest from the test piece;
the sound absorption coefficient α is calculated according to the following formula: α=1- |r| 2 。
7. The sound absorption coefficient and sound insulation amount measuring device for sound wave oblique incidence material according to claim 4, wherein: the measuring method of the sound insulation amount measuring device for the sound wave oblique incidence material comprises the following steps:
1) The signal generator enables the loudspeaker to emit Gaussian white noise into the sound insulation amount measuring device of the sound wave oblique incidence material through the power amplifier;
2) The six-channel data acquisition card is connected with the microphone through the signal conditioner, and respectively acquires sound pressure signals at the position of the microphone and transmits the sound pressure signals to the computer;
3) The computer calculates the transmission coefficient of the material under each angle of incidence of sound waves after the four equal-diameter tee pipe fittings are placed in the test piece by using the sound insulation amount calculation formula, and the change curve of the sound insulation amount along with the frequency.
8. The sound absorption coefficient and sound insulation amount measuring device of sound wave oblique incidence material according to claim 7, wherein: the transmission coefficient and the sound insulation are calculated as follows: transmission coefficient t p Calculated according to the following formula:
the sound insulation TL is calculated according to the following formula: tl= -20lg|t p |
Wherein x is 1 For the distance x between the test piece on the sound transmission tube and the reflecting tube and the far-end microphone, namely the distance x between the sound transmission tube and the microphone on the reflecting tube furthest from the test piece 2 For the distance x between the test piece on the sound transmission tube and the reflecting tube and the near-end microphone, namely the microphone on the sound transmission tube and the reflecting tube closest to the test piece 3 X is the distance between the test piece on the refraction tube and the near-end microphone 4 P is the distance between the test piece on the refraction tube and the far-end microphone 1 To be away from the test piece x 1 Sound pressure sum, P collected by two microphones at a location 2 To be away from the test piece x 2 Sound pressure sum, P collected by two microphones at a location 3 To be away from the test piece x 3 Sound pressure, P, collected by microphones at locations 4 To be away from the test piece x 4 The sound pressure picked up by the microphone at the location,
for the amplitude of the complex sound pressure of the incident wave, < >>
The amplitude of the complex sound pressure of the transmission wave, k is the complex wave number of the sound wave, s is the distance between the sound transmission tube, the reflecting tube and the two microphones on the transmission tube, and t p TL is the sound insulation amount, which is the transmission coefficient. />
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