CN114414664A - Sound absorption coefficient testing device and method based on embedded control system and short sound tube - Google Patents
Sound absorption coefficient testing device and method based on embedded control system and short sound tube Download PDFInfo
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Abstract
The invention provides a sound absorption coefficient testing device and method based on an embedded control system and a short sound tube. The embedded control system gives a pulse excitation signal to the DA conversion circuit through the singlechip, the loudspeaker unit acquires the signal to form a sound field in the short sound tube, and the microphone acquires the sound field of a sound absorption material sample in the short sound tube; after the signals are conditioned by the signal conditioning circuit and the AD sampling circuit, the sound absorption coefficient of the material is calculated by a single chip microcomputer algorithm. The whole test system is simple and easy to use, high in test speed and low in cost, is a portable and efficient sound absorption coefficient test means, and simultaneously ensures the test precision and reliability.
Description
Technical Field
The invention relates to the field of sound absorption coefficient measurement, in particular to a device and a method for realizing sound absorption coefficient measurement by matching short and short sound tubes based on an embedded control system.
Background
The sound absorption coefficient of the material is widely applied to various fields of building materials, traffic noise, aerospace, military wars and the like. In some buildings with limited environmental noise, acoustic material settings of environments such as music halls, movie theaters and the like need to measure the sound absorption coefficient; meanwhile, the noise problem when the airplane is taken is increasingly prominent due to factors such as increasing the speed of the airplane and increasing the power, the noise in the cabin mainly comes from engine noise, electric power system, fuel system, exhaust system and boundary layer noise, and in order to reduce the cabin noise of the airplane and improve the comfort of taking the airplane, the sound absorption technology is a technology with good effect in the passive noise reduction technology, and the sound absorption material is paved on the inner wall of the cabin of the airplane, so that the reflected sound wave can be absorbed, and a good noise reduction effect is achieved. In order to reasonably and effectively select a proper sound absorption material or structure, the acoustic performance parameter sound absorption coefficient of the sound absorption material or structure must be mastered; in automobile design, engineers evaluate the comfort of an automobile by testing the sound absorption coefficient of materials in the automobile; in modern sea wars, submarine radiation noise directly influences stealthy performance of a submarine, transient change of a battlefield and a severe environment are greatly tested, operation capacity of the submarine is closely related to sound stealthy capacity of the submarine, and laying of sound absorption materials can effectively improve the stealthy capacity of the submarine. Therefore, in various fields of air and underwater sound, the acoustic performance test of the material plays an irreplaceable role in the design, development and use of the acoustic material.
In engineering practice, the test of the sound absorption coefficient of the current material can only be carried out in a laboratory, how to detect the sound absorption coefficient of the material on site becomes an important problem, and a set of novel convenient on-site detection device becomes a key for solving the problem. The impedance tube is an important platform for measuring acoustic performance, and the sound absorption coefficient of a material can be effectively measured on the platform by a transfer function method, a PU vector probe method, a broadband pulse method and other methods, but the impedance tube on the market is generally large in size and inconvenient to carry, needs support of matched equipment and software, and cannot be used for field measurement. In order to realize field test and portability, a set of short sound tube and a test system with smaller size are needed, and an embedded system is used for replacing a computer and acquisition equipment, so that a portable field sound absorption coefficient test system device is realized in a real sense.
In the known standing wave tube sound absorption coefficient test method, the invention patent with application publication number CN 110501427A named as a portable device and a measurement method for measuring the sound absorption coefficient of a material based on a short sound tube pulse method generates a Butterworth broadband pulse signal at a through hole close to the surface of a loudspeaker, then performs Fourier transform according to extracted direct waves and reflected waves, calculates the acoustic impedance, and calculates the sound absorption coefficient of the material according to the acoustic impedance. However, this method requires the support of a computer and a professional acquisition front end, requires a special power amplifier, and requires a power supply indoors to complete the test. Meanwhile, the method needs to generate standard pulse sound firstly and then test, the steps are complicated, and the test precision can be influenced under the condition that the pulse sound is generated nonstandard. Therefore, in order to solve the two problems, the invention firstly adopts a set of embedded hardware system to integrate the algorithm and the control, and forms a set of testing device with the short sound tube, and the transfer function method and the pulse method are combined for use to test the sound absorption coefficient, thereby ensuring the precision and having better testing efficiency and testing speed.
Disclosure of Invention
The invention aims to provide a sound absorption coefficient testing device and method based on an embedded control system and a short sound tube, wherein the short sound tube can realize sound absorption coefficient measurement by a transfer function method and a broadband pulse method. The whole test system is simple and easy to use, high in test speed and low in cost, is a portable and efficient sound absorption coefficient test means, and simultaneously ensures the test precision and reliability.
In order to achieve the purpose, the invention is realized by the following technical scheme:
on one hand, the invention provides a sound absorption coefficient testing device based on an embedded control system and a short sound tube, which comprises the embedded control system and the short sound tube;
the short sound tube comprises a loudspeaker unit, a short sound tube body and a microphone;
the embedded control system is respectively connected with the loudspeaker unit and the microphone; the loudspeaker unit and the microphone are respectively connected with the short sound tube main body;
and a test material sample is placed at the pipe orifice of the short sound pipe main body, and the test material sample is tested through the embedded control system.
In the scheme, the embedded control system comprises a signal conditioning circuit, an AD sampling circuit, a singlechip and a DA conversion circuit which are sequentially connected, wherein the signal conditioning circuit is connected with a microphone, and the DA conversion circuit is connected with a loudspeaker unit; the lithium battery pack and the power circuit are connected with the signal conditioning circuit, the AD sampling circuit, the single chip microcomputer and the DA conversion circuit.
In the above scheme, the lithium battery pack and the power circuit comprise the lithium battery circuit and the three-level power circuit, and the output power of the lithium battery circuit is connected with the three-level power circuit which is connected in sequence.
In the above scheme, the signal conditioning circuit comprises a constant current source circuit, a voltage amplifying circuit and an output buffer circuit which are connected in sequence.
In the scheme, the AD sampling circuit comprises an AD conversion chip U8, and a pin of the AD conversion chip U8 is connected to the output of the signal conditioning circuit; a pin is connected with a filter capacitor C28 in parallel and then is connected to a reference source chip U10; the pin of the reference source chip U10 is connected with a power supply +3.3V and a filter capacitor C30; the pin is connected with a resistor R19 in series and then connected with a power supply of +5V, and the pin is connected with a power supply of +3.3V and a grounding capacitor C32.
In the scheme, the DA conversion circuit comprises a DA conversion chip U9 and an operational amplifier U11A; the DA conversion chip U9 is connected with the resistor R21 in series and the ground resistor R22 in parallel and then is connected with the homodromous input end of the operational amplifier U11A; a pin of the DA conversion chip U9 is connected with a power supply +5V and a grounding capacitor C29, a pin 10 of the DA conversion chip U9 outputs REF voltage, and the REF voltage is connected with a grounding capacitor C27 and a series resistor R18 and then is connected with the reverse input end of an operational amplifier U11A;
a resistor R17 is connected between the output end and the inverting input end of the operational amplifier U11A, and the output end of the operational amplifier U11A is connected with the resistor R20 in series and is connected with a ground capacitor C31 in parallel and then is connected with a pin 1 of the socket of the loudspeaker unit; pins of U11A are connected to power supply + -12V respectively.
In another aspect of the present invention, a sound absorption coefficient testing method based on an embedded control system and a short sound tube is provided, which includes the following steps:
s1, placing a sound absorption material to be detected at the pipe orifice of the short sound pipe, and installing a microphone on the wall of the short sound pipe and connecting the microphone with the embedded control system;
s2, after the embedded control system is powered on and initialized, starting the timer interrupt of the singlechip;
s3, the embedded control system gives a pulse excitation signal to the DA conversion circuit through the singlechip, the loudspeaker unit obtains the signal to form a sound field in the short sound tube, and the microphone collects the sound field of the sound absorption material sample in the short sound tube;
and S4, after the signal is conditioned by the signal conditioning circuit and the AD sampling circuit, the sound absorption coefficient of the material is calculated by a single chip microcomputer algorithm.
In the scheme, the sound absorption material sample is cut into a round sample with the diameter of 9.75-10.25mm, the sound absorption material sample is perpendicular to the pipe shaft of the short sound pipe wall, and the sample is tightly attached to the pipe cover.
Compared with the traditional sound absorption coefficient test system, the sound absorption coefficient test system has the following beneficial effects:
the invention provides a device for testing the sound absorption coefficient of a material by utilizing an embedded system and a portable short sound tube, and the device effectively solves the problems of complicated testing steps and inconvenience in carrying of testing equipment in the sound absorption coefficient testing industrial process by introducing the embedded system and the short sound tube.
According to the invention, a single chip microcomputer in the embedded system generates a time-domain broadband pulse digital excitation signal, the digital signal is converted into an analog voltage signal through a DA conversion circuit in the embedded system, the analog voltage signal drives a loudspeaker unit to sound, a sound wave signal is parallelly transmitted in the short sound tube main body, and the sound wave signal is absorbed and reflected by a material at the opening of the short sound tube to form a sound field in the tube. A microphone arranged on the wall of the short sound tube main body collects sound pressure signals in the tube and converts the sound pressure signals into voltage signals, a signal conditioning circuit in the embedded system supplies power to the microphone and conditions the voltage signals obtained by the microphone, and the conditioned voltage signals enter an AD sampling circuit to be sampled, quantized and coded and then converted into digital response signals; the single chip microcomputer receives the digital response signal and calculates, and the sound absorption coefficient of the material sample is obtained by calculating the sound transmission relation at the measuring point of the microphone.
The invention provides a method for constructing a sound absorption coefficient test system by an embedded system, which has flexibility and universality and can be transplanted and utilized in different sensor test systems. Compared with the traditional scheme, the method has the advantages of high efficiency, high reliability, low cost and portability.
Drawings
FIG. 1 is a schematic view of the construction of a sound absorption coefficient testing apparatus;
FIG. 2 is a block diagram of an embedded control system;
FIGS. 3(a) -3(d) are schematic diagrams of lithium battery packs and power supply circuits;
FIGS. 4(a) -4(c) are signal conditioning circuit diagrams;
FIG. 5 is an AD sampling circuit diagram;
fig. 6 is a DA conversion circuit diagram;
FIG. 7 is a flow chart of a sound absorption coefficient testing method;
FIG. 8 is a comparison of the sound absorption coefficient test curves of the test device and the B & K system for a certain sponge standard sample.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
As shown in fig. 1, the portable sound absorption coefficient testing device based on the embedded control system and the short sound tube provided by the invention comprises the embedded control system 1 and the short sound tube.
The short sound tube comprises a loudspeaker unit 2, a short sound tube main body 4 and a microphone 5; the embedded control system 1 is respectively connected with a loudspeaker unit 2 and a microphone 5; the speaker unit 2 and the microphone 5 are respectively connected with the short sound tube main body 4; the test material sample 6 is placed at the orifice of the short sound tube main body 4, and the test material sample 6 is tested through the embedded control system 1.
As shown in fig. 2, the embedded control system 1 includes a signal conditioning circuit 20, an AD sampling circuit 30, a single chip and a DA conversion circuit 40, which are connected in sequence, the signal conditioning circuit 20 is connected with the microphone 5, and the DA conversion circuit 40 is connected with the speaker unit 2; the lithium battery pack and power supply circuit 10 is connected with the signal conditioning circuit 20, the AD sampling circuit 30, the single chip microcomputer and the DA conversion circuit 40.
The lithium battery pack and the power circuit comprise a lithium battery circuit and a three-level power circuit, and an output power supply of the lithium battery circuit is connected with the three-level power circuit which is connected in sequence.
As shown in fig. 3(a), the lithium battery circuit is connected in parallel with an input filter capacitor C8 through a lithium battery pack pin 1, the lithium battery pack pin 2 is connected to the analog ground, and one end of the pin 1 outputs +24V power to be connected to a three-stage power circuit. 24V voltage is provided by the lithium battery pack, the instant working current of the lithium battery pack is 4A, the continuous power supply current stably supports 2A output, the power reaches 48W, and large-capacity aluminum electrolysis is connected between the power supply 24V and the ground to play a role in energy storage, buffering and stabilizing input voltage.
As shown in fig. 3(b), the first stage power circuit includes a DC-DC power module U3, a power supply +24V parallel input capacitor C9, and pin 1 of the series-connected DC-DC power module U3, pin 2 and pin 4 of the power module U3 are connected to analog ground, pin 3 of the power module U3 outputs power supply +12V, and pin 5 outputs power supply-12V, a series output capacitor C4 between pin 3 and pin 4 of the power module U3, and a series output capacitor C10 between pin 4 and pin 5; the analog ground is connected to ground through a 0 ohm resistor.
The U3 realizes voltage conversion, U3 is a DC/DC power supply module VRA2412YMD-6WR3, power supply +24V provided by a lithium battery pack is converted into power supply +/-12V, and filter capacitors C9, C4 and C10 are connected between input and output pins of the power supply module and the ground in series to reduce input and output ripples to be below 60 mv.
As shown in fig. 3(C), the second stage power circuit includes a DC-DC chip U1, a power supply +12V series schottky diode D2 and two parallel capacitors C11 and C12 connected to analog ground, a negative series resistor of the schottky diode D2 is connected to pin 4 of the DC-DC chip U1, and a pin of U1 is connected to pin 4 and pin 5 through a resistor R3; pin 1 and pin 6 of U1 are connected through a capacitor C1, pin 6 of U1 is connected in series with the cathode of a Schottky diode and then is connected to an analog ground, the cathode of the Schottky diode is connected in series with a power inductor L1 and two output capacitors C7 and C6 which are connected in parallel and then is connected to the analog ground, and the anode of the capacitor C6 outputs +5V power; pin 2 and pin 3 of U1 are connected through a resistor R2, and are connected to a power supply +5V after being connected in series with a resistor R2 and a resistor R4 in an analog manner.
U1 realizes voltage conversion, U1 is DC-DC chip MP2359, converts +12V of power supply provided by DC/DC power module VRA2412YMD-6WR3 into +5V of power supply, Schottky diode D1 releases current, and releases the current to output capacitors C7 and C6 after conversion of inductor L1, the power output end adopts ceramic output capacitor C7 with ESR less than 100 milliohm to make the circuit work stably, and the current in inductor L1 rises at the rate of 12V/100 uH.
As shown in fig. 3(d), the third stage power circuit includes a DC-DC chip U2, a power supply +5V is connected to pin 3 of LDO chip U2, pin 1 of U2 is connected to analog ground, and a capacitor C5 is connected in series between pin 3 and pin 1 of U2; and after the pin 2 and the pin 4 of the U2 are short-circuited, the power supply +3.3V is output, and the power supply +3.3V is connected with two filter capacitors in series and then is connected with the analog ground.
Because the required precision of the +3.3V power supply voltage required by the interior of the single chip microcomputer is +/-10%, the voltage between the +5V power supply and the +3.3V power supply is less than 3V, the LDO chip AMS-1117 is selected to realize high-precision voltage conversion, namely U2 in the figure, the precision of the output voltage is 1.5%, the capacitor C5 is an input filter capacitor, the noise of the input voltage can be reduced, and the capacitors C2 and C3 are output filter capacitors, so that the output voltage is more stable.
The signal conditioning circuit 20 includes a constant current source circuit, a voltage amplifying circuit, and an output buffer circuit, which are connected in sequence.
As shown in fig. 4(a), the constant current source circuit includes a constant current source chip U7, pin 4 and pin 1 of U7 are connected to +24V of power supply, pin 4 of U7 is connected in parallel with a capacitor filter C26, pin 2, pin 3, pin 7 and pin 6 of the constant current source chip U7 are connected to +24V of power supply through a resistor R11, and a resistor R6 series diode D4 is connected in parallel with a resistor R11; the cathode of the diode D4 is connected to the anode of the capacitor C14, pin 1 of the microphone socket is connected in parallel to the capacitor C14, pin 2 of the microphone socket is connected to ground, and the capacitor C14 is connected in parallel to the resistor R10 to output a microphone voltage Signal 1.
The microphone is powered by a constant-current 4mA power supply mode, so that a constant-current source chip LM334 is required to provide 4mA driving current, the constant-current source chip LM334 needs +24V power supply input, an input pin bypass capacitor C26 plays a role in energy storage buffering, resistors R6 and R7 adjust the output current to 4mA, the resistance value of R7 is ten times of that of R6, a diode D4 outputs constant current, a microphone socket receives constant current and then feeds back a microphone voltage signal, a capacitor C14 is a blocking capacitor and filters a front-stage signal direct-current component, and a resistor R10 plays a role in impedance matching.
As shown in fig. 4(b), the voltage amplifying circuit includes a first-stage operational amplifier U4B, an instrumentation amplifier U5, and a second-stage operational amplifier U6A.
The microphone voltage Signal 1 is connected to the homodromous input end of a first-stage operational amplifier U4B, and the inverting input end of the operational amplifier U4B is connected with the output end; the output end of U4B is connected with a DC blocking capacitor C19 in series and then connected with a resistor R16 and the positive input end of an instrumentation amplifier U5, the negative input end of the instrumentation amplifier U5 is grounded with a pin 5, an adjusting resistor R5 is connected between a pin 1 and a pin 8 of the instrumentation amplifier, and the output end of the instrumentation amplifier U5 is connected with a resistor R13 in series and then connected with the inverting input end of a second-stage operational amplifier U6A; the homodromous input end of the second-stage operational amplifier U6A is connected with the matching resistor R14 in series and then grounded, the inverting input end of U6A is connected with the resistor R9 in series to power-12V, the output end of U6A and the inverting input end of U6A are connected with the feedback resistor R7 in series, and the output end of the second-stage operational amplifier outputs an amplified voltage Signal 2; pin 4 of U4B, pin 4 of U5 and pin 4 of U6A are connected with a power supply of-12V and are respectively connected with capacitors C21, C22 and C23 in parallel to the ground, and pin 8 of U4B, pin 7 of U5 and pin 8 of U6A are connected with a power supply of +12V and are respectively connected with capacitors C16, C15 and C18 in parallel to the ground.
The signal 1 output in fig. 4(a) is input to the equidirectional input end of the first-stage operational amplifier U4B, the output end of U4B is connected to the inverting input end to form an input buffer, which plays a role of matching input impedance, the signal passes through the buffer and then passes through the dc blocking capacitor C19, the bias voltage is filtered, the resistor R16 provides a dc loop of bias current, so that the instrumentation amplifier U5 works stably, the resistor R5 adjusts the amplification factor of U5 to 10 times, the signal is amplified and then input to the second-stage operational amplifier U6A, the U6A and the resistors R13, R9 and R7 form an inverting amplifier circuit, and the signal 2 is output after providing a dc bias voltage of + 5V. In the figure, U4B and U6A are operational amplifiers NE5532, and U5 is instrumentation amplifier AD 620.
As shown in fig. 4(c), the output buffer circuit includes a third stage operational amplifier U6B and a second stage operational amplifier U4A. The amplified voltage Signal 2 is connected to the homodromous input end of a third-stage operational amplifier U6B, the output end of U6B is connected with the inverting input end, the output end of U6B is connected with a three-terminal Schottky diode D3 in parallel, the anode of the three-terminal Schottky diode D3 is grounded, the cathode of the three-terminal Schottky diode D3 is connected with the output end and the inverting input end of an operational amplifier U4A, the homodromous input end of U4A is connected with a resistor R8 and a resistor R12, a resistor R8 is grounded, and a resistor R12 is connected with +12V of a power supply; the output end of the third-stage operational amplifier U6B is connected in series with a resistor R15 and a parallel capacitor C24 and then outputs a conditioning voltage Signal 3; pin 4 of U6B and pin 4 of U4A are both connected to power supply 12V and connected in parallel to capacitors C17 and C25 respectively to ground, and pin 8 of U6B and pin 8 of U4A are both connected to power supply +12V and connected in parallel to capacitors C20 and C13 respectively to ground.
The Signal 2 output in fig. 4(b) is input into a voltage follower formed by a third-stage operational amplifier U6B, the voltage follower plays a role of output impedance matching, after the Signal is followed by voltage, the Signal passes through a three-terminal schottky diode D3, the lower limit of the voltage of a Signal is clamped to 0V by grounding of the cathode of the three-terminal schottky diode D3, the anode of the three-terminal schottky diode D3 is connected with the follower formed by the operational amplifier U4A, the output voltage of the follower is +10V, the upper limit of the voltage of the Signal is clamped to +10V, the clamping voltage floats up and down by 0.2V according to the conduction voltage drop of the schottky diode, the Signal passes through a low-pass filter formed by a resistor R15 and a capacitor C24 after being clamped by overvoltage, the cutoff frequency of the low-pass filter is set to 60KHz, and the Signal is filtered and noise-reduced and then output Signal 3. The operational amplifiers U6B and U4A are NE 5532.
As shown in fig. 5, the AD sampling circuit 30 includes an AD conversion chip U8, a pin 49 of the AD conversion chip U8 is connected to the Signal conditioning circuit 20 to output Signal 3, a pin 50 is connected to an analog ground, a pin 34 is connected in series with a resistor R23 to the ground, a pin 48 is connected to a power supply +5V, a pin 42 is connected in parallel with a filter capacitor C28 and then connected to a pin 2 of a reference source chip U10, a pin 3 of the reference source chip U10 is connected to the ground, and a pin 1 is connected to the power supply +3.3V and the filter capacitor C30; pin 3, pin 4 and pin 5 of the AD conversion chip are grounded, pin 6 is connected with a power supply +5V after being connected with a resistor R19 in series, and pin 23 is connected with the power supply +3.3V and a grounded capacitor C32.
The final output signal 3 of fig. 4(C) enters a pin 49 of an AD sampling chip U8, a pin 34 of a U8 is connected with a pull-down resistor to ground to select an external reference power supply, a pin 42 of a U8 is a reference voltage input port, a +2.5V voltage with a precision of ± 1% is generated by a reference source chip U10 and is supplied to the pin 42 of the U8, the reference source chip U10 needs an input of +3.3V, a capacitor C28 is an output filter capacitor, which can further stabilize the reference voltage, and a capacitor C30 is an input filter capacitor, which can stabilize the input of the reference source chip U10. And pins 3, 4 and 5 of the AD sampling chip U8 are grounded, the chip is set to be in a non-oversampling mode, and pin 6 is connected with a pull-up resistor to be set to be in a serial input mode. U8 is AD sampling chip AD7606, and AD7606 passes through SPI communication interface connection with singlechip STM32F429, and it is used for receiving AD7606 conversion and obtains digital signal to the inside further operation of singlechip.
As shown in fig. 6, the DA conversion circuit 40 includes a DA conversion chip U9 and an operational amplifier U11A. Pin 9 of the DA conversion chip U9 is connected with a power supply +5V and a grounding capacitor C29, pin 1 of the DA conversion chip U9 is connected with a resistor R21 in series and a grounding resistor R22 in parallel and then is connected with the homodromous input end of an operational amplifier U11A; a pin 10 of the DA conversion chip U9 outputs a REF voltage, and is connected with a grounded capacitor C27 and a series resistor R18 in parallel and then is connected with the reverse input end of an operational amplifier U11A; the series resistor R17 is connected between the output end and the inverting input end of the operational amplifier U11A, the output end of the operational amplifier U11A is connected with the resistor R20 in series and is connected with the ground capacitor C31 in parallel, then the pin 1 of the loudspeaker unit socket is connected, and the pin 2 of the loudspeaker unit socket is connected with the ground. Pin 4 of U11A is connected to power supply-12V, and pin 8 of U11A is connected to power supply + 12V.
Singlechip STM32F429 passes through SPI communication interface with DA conversion chip U9 and connects, and U9 is DA conversion chip DAC8563, and U9's pin 9 connects power supply +5V, and the input precision of voltage is 5%, and electric capacity C29 is input filter capacitor. U9 receives the digital signal of singlechip STM32F429 and converts into analog voltage signal through SPI communication mode, and analog voltage signal is exported by pin 1, and pin 10 exports +5V reference voltage. The analog voltage signal output from the U9 pin 1 enters a differential proportion amplifying circuit composed of an operational amplifier U11A, a resistor R21, a resistor R22, a resistor R18 and a resistor R17, the circuit modulates the analog output signal into an output range of 0-10V, the modulated signal passes through a low-pass filter composed of resistors R20 and C31, the cut-off frequency of the filter is set to 10KHz, the analog voltage signal is output after being filtered and is connected to a loudspeaker unit by a coaxial cable to drive the loudspeaker to produce sound, and the signal-to-noise ratio of the sound source signal is larger than 80 dB.
As shown in fig. 7, the following provides a portable sound absorption coefficient testing method based on an embedded control system and a short sound tube, the measurement includes the following steps:
and S1, placing a sound absorption material to be detected at a specific position of the short sound tube, and installing a microphone on the wall of the short sound tube and connecting the microphone with the embedded control system. The sound absorbing material sample needs to be cut into a small round piece with a diameter of 9.75-10.25mm to ensure that the sample should not be compressed too much or mounted so tightly that the sample bulges, and mounted perpendicular to the short sound tube axis with the sample tightly against the tube cap.
And S2, after the system is powered on and initialized, starting the timer interrupt of the singlechip. After the system is powered on, the system is in a waiting state before receiving the command, the tester is known to send out a test command, and the response time of the device for receiving the command does not exceed 20 ms; and after receiving the command, the single chip microcomputer opens a timer to interrupt, and the period of timer interrupt is set to be 30.5 us.
S3, the embedded control system gives a pulse excitation signal to the DA conversion circuit through the singlechip, the loudspeaker unit obtains the signal to form a sound field in the short sound tube, and the microphone collects the sound field of the sound absorption material sample in the short sound tube;
s4, conditioning the signal through a signal conditioning circuit and an AD sampling circuit, synchronously starting a signal acquisition and signal sending function in a timer interrupt function, generating a digital excitation signal by a singlechip, converting the digital excitation signal into an analog voltage excitation signal by a DA conversion circuit, exciting a loudspeaker unit to sound, wherein the signal-to-noise ratio of the signal is not less than 65dB, and the conversion time of each time is not more than 3 us; meanwhile, analog voltage signals received by the microphone are converted into digital signals through the AD sampling circuit after passing through the signal conditioning circuit and are transmitted to the single chip microcomputer, and each sampling time is not more than 4 us. And finishing data acquisition and closing timer interruption after the execution times of the timer interruption is not less than 32768 times, wherein the total time of the data acquisition is not more than 1 s.
And calculating the acquired data by using an algorithm unit in the single chip microcomputer, wherein the calculation time does not exceed 1s, and the data obtained by the calculation of the single chip microcomputer is the sound absorption coefficient of the sound absorption material sample to be detected.
In this example, the sound absorption coefficient test of a certain sponge sample is performed according to the test flow, the test curve is shown in fig. 8, meanwhile, in order to verify the measurement accuracy and accuracy of the device, the sound absorption coefficient test of the same sample is performed by using a 3050 system of B & K company under the same conditions, the test results of the two methods are shown in fig. 8, it can be seen that the sound absorption curves are well matched, and the validity and feasibility of the system are verified.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that, for those skilled in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be construed as the protection scope of the present invention.
Claims (10)
1. A sound absorption coefficient testing device based on an embedded control system and a short sound tube is characterized by comprising an embedded control system (1) and a short sound tube;
the short sound tube comprises a loudspeaker unit (2), a short sound tube main body (4) and a microphone (5);
the embedded control system (1) is respectively connected with the loudspeaker unit (2) and the microphone (5); the loudspeaker unit (2) and the microphone (5) are respectively connected with the short sound tube main body (4);
the pipe orifice of the short sound tube main body (4) is used for placing a test material sample (6), and the test material sample (6) is tested through the embedded control system (1).
2. The device for testing the sound absorption coefficient based on the embedded control system and the short sound tube is characterized in that the embedded control system (1) comprises a signal conditioning circuit (20), an AD sampling circuit (30), a single chip microcomputer and a DA conversion circuit (40) which are sequentially connected, wherein the signal conditioning circuit (20) is connected with a microphone (5), and the DA conversion circuit (40) is connected with a loudspeaker unit (2);
the device also comprises a lithium battery pack and a power circuit (10) which are connected with the signal conditioning circuit (20), the AD sampling circuit (30), the single chip microcomputer and the DA conversion circuit (40).
3. The device for testing the sound absorption coefficient based on the embedded control system and the short sound tube as claimed in claim 2, wherein the lithium battery pack and power circuit (10) comprises a lithium battery circuit and a three-level power circuit, and an output power of the lithium battery circuit is connected with the three-level power circuit which is connected in sequence.
4. The device for testing the sound absorption coefficient based on the embedded control system and the short sound tube as claimed in claim 3, wherein the lithium battery circuit is connected in parallel with the input filter capacitor C8 through the lithium battery pack, one end of the lithium battery circuit is grounded, the other end of the lithium battery circuit outputs +24V power, and the lithium battery circuit is connected to a three-stage power circuit, and the three-stage power circuit comprises:
the first stage power supply circuit comprises a DC-DC power supply module U3, an input capacitor C9 connected with a +24V power supply in parallel; the output end of the U3 is connected in parallel with output capacitors C4 and C10 to output +/-12V power respectively;
the second-stage power supply circuit comprises an input end of a DC-DC chip U1, a resistor R2 is connected in parallel with the input end of the DC-DC chip U1, and a resistor R4 is connected in series and then connected with a +5V power supply; the other input end and the output end are connected with the capacitor C11 and the diode D1 in series and then are grounded; the diode D1 is connected in series with the power inductor L1 and the output capacitors C7 and C6 which are connected in parallel and then grounded, and the positive electrode of the capacitor C6 outputs a +5V power supply; the input end of the DC-DC chip U1 is connected with a series resistor R3 and another pin in parallel and then connected with a group of capacitors C11 and C12 in parallel to be grounded, and is connected with a Schottky diode D2 in series to be connected with a +12V power supply;
the third-stage power circuit comprises an LDO chip U2, wherein the input end of the LDO chip U2 is connected with a capacitor C5 in parallel to connect a +5V power supply, the output end of the LDO chip U2 is short-circuited and then outputs a +3.3V power supply, and the power supply +3.3V power supply is grounded after being connected with two filter capacitors C2 and C3 in series.
5. The sound absorption coefficient testing device based on the embedded control system and the short sound tube as claimed in claim 1, wherein the signal conditioning circuit (20) comprises a constant current source circuit, a voltage amplifying circuit and an output buffer circuit which are connected in sequence.
6. The device for testing the sound absorption coefficient based on the embedded control system and the short sound tube as claimed in claim 5, wherein the constant current source circuit comprises a constant current source chip U7 with an input end connected with +24V of a power supply, an input/output pin connected with resistors R11 and R6 in parallel, a diode D4 connected with a capacitor C14 and a microphone in parallel, a capacitor C14 connected with a resistor R10 in parallel and outputting a microphone voltage Signal 1;
the voltage amplifying circuit comprises a first-stage operational amplifier U4B, an instrumentation amplifier U5 and a second-stage operational amplifier U6A, and a microphone voltage Signal 1 is connected to the first-stage operational amplifier U4B;
the output end of the first-stage operational amplifier U4B is connected with a DC blocking capacitor C19, and a resistor R16 is connected with the input end of an instrumentation amplifier U5; the output end of the instrumentation amplifier U5 is connected with the resistor R13 and the input end of the second-stage operational amplifier U6A;
the inverting input end of the operational amplifier U4B is connected with the output end; a regulating resistor R5 is connected between pins of the instrumentation amplifier U5; the inverting input end of the second-stage operational amplifier U6A is connected with a resistor R9 in series to a power supply of-12V, and the output end of U6A and the inverting input end of U6A are connected with a feedback resistor R7 in series;
the same-direction input end of the second-stage operational amplifier U6A is connected with the ground after being connected with the matching resistor R14 in series; the output end of the second-stage operational amplifier U6A outputs an amplified voltage Signal Signal 2;
pins of the first-stage operational amplifier U4B, the instrumentation amplifier U5 and the second-stage operational amplifier U6A are all connected with a power supply of-12V and are respectively connected with capacitors C21, C22 and C23 to the ground in parallel; pins of U4B, U5 and U6A are all connected with a power supply of +12V and are respectively connected with capacitors C16, C15 and C18 in parallel to the ground;
the output buffer circuit comprises a third-stage operational amplifier U6B and a fourth-stage operational amplifier U4A, the input end of the third-stage operational amplifier U6B is connected with a Signal 2, and the rear end of an output end of the third-stage operational amplifier U6 is grounded with the rear end of a three-terminal Schottky diode D3 connected between the output end of the fourth-stage operational amplifier U4A;
the third-stage operational amplifier U6B and the fourth-stage operational amplifier U4A are both connected with a power supply-12V and are respectively connected with capacitors C17 and C25 in parallel to the ground; the pin of U6B and the pin of U4A are both connected with a power supply of +12V and are respectively connected with capacitors C20 and C13 to the ground in parallel;
the same-direction input end of the U4A is connected with a resistor R8 and a resistor R12, the resistor R8 is grounded, and the resistor R12 is connected with a power supply + 12V;
the output end of the third-stage operational amplifier U6B is connected in series with a resistor R15 and a parallel capacitor C24 and then outputs a conditioning voltage Signal 3.
7. The device for testing the sound absorption coefficient based on the embedded control system and the short sound tube as claimed in claim 1, wherein the AD sampling circuit (30) comprises an AD conversion chip U8, and a pin of the AD conversion chip U8 is connected to the Signal conditioning circuit (20) to output Signal 3; a pin 34 is connected with a resistor R23 in series to the ground, a pin 48 is connected with a power supply of +5V, and a pin 42 is connected with a reference source chip U10 after being connected with a filter capacitor C28 in parallel; pin 3 of the reference source chip U10 is grounded, pin 1 is connected with the power supply +3.3V and the filter capacitor C30; pins 3, 4 and 5 of the AD conversion chip are grounded, pin 6 is connected with a power supply +5V after being connected with a resistor R19 in series, and pin 23 is connected with the power supply +3.3V and a grounded capacitor C32.
8. The device for testing sound absorption coefficient based on embedded control system and short sound tube as claimed in claim 1, wherein the DA conversion circuit (40) comprises a DA conversion chip U9 and an operational amplifier U11A; the pin of the DA conversion chip U9 is connected with a power supply +5V and a grounding capacitor C29, and the DA conversion chip U9 is connected with a resistor R21 in series and is connected with a grounding resistor R22 in parallel and then is connected with the homodromous input end of an operational amplifier U11A; a pin 10 of the DA conversion chip U9 outputs a REF voltage, and is connected with a grounded capacitor C27 and a series resistor R18 in parallel and then is connected with the reverse input end of an operational amplifier U11A;
a resistor R17 is connected between the output end and the inverting input end of the operational amplifier U11A, and the output end of the operational amplifier U11A is connected with the resistor R20 in series and is connected with a ground capacitor C31 in parallel and then is connected with a pin 1 of the socket of the loudspeaker unit; pins of U11A are connected to power supply + -12V respectively.
9. The method for testing the sound absorption coefficient of the device according to any one of claims 1-8 based on the embedded control system and the short sound tube is characterized by comprising the following steps:
s1, placing a sound absorption material to be detected at the pipe orifice of the short sound pipe, and installing a microphone on the wall of the short sound pipe and connecting the microphone with the embedded control system;
s2, after the embedded control system is powered on and initialized, starting the timer interrupt of the singlechip;
s3, the embedded control system gives a pulse excitation signal to the DA conversion circuit through the singlechip, the loudspeaker unit obtains the signal to form a sound field in the short sound tube, and the microphone collects the sound field of the sound absorption material sample in the short sound tube;
and S4, after the signal is conditioned by the signal conditioning circuit and the AD sampling circuit, the sound absorption coefficient of the material is calculated by a single chip microcomputer algorithm.
10. The method for testing the sound absorption coefficient based on the embedded control system and the short sound tube is characterized in that a sound absorption material sample (6) is cut into a round sample with the diameter of 9.75-10.25mm, the sound absorption material sample is perpendicular to the tube wall and the tube cover is tightly attached to the sample.
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