CN207881835U - A kind of anechoic tank, for acoustic metrology - Google Patents

Abstract

The utility model discloses a muffler pool for acoustic measurement. The device is mainly composed of a pool body, a sound-absorbing material layer, a mechanical device and a control system. The pool structure adopts reinforced waterproof concrete; the sound-absorbing material layer adopts sound-absorbing wedges, and steel bars with hooks are installed inside the pool, and the sound-absorbing wedges are installed in plastic shells and hung in the hooks, and the sound-absorbing wedge shells are directly laid on the bottom of the pool body, the thickness of the sound-absorbing material layer is about 250mm. The mechanical device is divided into an automatic scanning device and an installation platform. The automatic scanning device is used for the scanning motion control of the hydrophone. It adopts a gantry-type four-degree-of-freedom linear module structure, which can realize the translation of the X, Y, and Z axes and the movement around the Z axis. The automatic rotation, the mounting platform is used to install the standard sound source or the calibrated transducer, array. The device is mainly used for performance test calibration of underwater acoustic and ultrasonic transducers and their arrays, material sound performance test and acoustic test measurement method research; it effectively ensures the measurement accuracy and expands the measurement range.

Description

An anechoic pool for acoustic metering

technical field

The utility model belongs to the technical field of sound field measurement, in particular to an underwater acoustic measurement device.

Background technique

Ultrasound is a sound wave with a frequency higher than 20,000 Hz. It has good directionality and strong penetrating ability. It is easy to obtain concentrated sound energy and has a long distance in water. It can be used for distance measurement, speed measurement, cleaning, welding, and stone breaking. , Sterilization, etc. There are many applications in medicine, military, industry, and agriculture.

Ultrasound has mechanical effects, cavitation effects, thermal effects and other biochemical effects. When the radiation amount Q of the focusing transducer reaches a certain intensity, not only thermal effects but also destructive cavitation effects may occur. The radiation dose Q is related to the sound power:

Q=E×t

Where E is the sound power, and t is the action time. The size of the rising power is particularly important. The sound power refers to the amount of sound energy per unit time when the sound wave passes through a specified area perpendicular to the propagation direction. In focused ultrasound, what people care about is the sound power out of the focus plane. The sound power cannot be directly measured at a certain position in the sound field, but can only be measured indirectly. The commonly used measurement methods include radiation force method, laser interferometry and sound pressure method.

The method of radiation force method appeared first, and most of the products commonly used in China to measure the output sound power of ultrasound are developed based on this principle. It is based on the basic principle of ultrasonic metrology, the ultrasonic signal acts on the receiving target in the measured field, and the sound power is calculated by using the relationship between the force and power on the receiving target, but this equipment has a great influence on the size of the receiving target and the size of the receiving target. The measurement position requirements are higher, and the manufacturing cost of this red equipment is higher.

Laser interferometry is to determine the radiated sound power by measuring the radiated sound source and mechanical parameters. The radiated power is determined by measuring the displacement amplitude of the surface of the radiating sound source. However, this method has high requirements for optical equipment, and the measurement of different types of sounding probes is not universal. For some probes, further research is needed to obtain the acoustic impedance expression.

The basis of the sound pressure method is to use a hydrophone to scan the radiation sound field of the equipment to obtain its sound pressure, and then obtain its sound power by integration, which is relatively simple to measure. However, due to the energy convergence of the focusing transducer, the sound pressure at the focal point is relatively large, and direct measurement with the hydrophone in the focal area will cause irreparable damage to the hydrophone and increase the measurement cost. For the measurement device, when using the hydrophone to measure the sound field of the underwater acoustic transducer, in order to ensure that the signal received by the hydrophone is moved and scanned underwater through the mechanical structure of the control device equipped with the hydrophone, so , it is particularly important to realize the three-dimensional movement of the hydrophone in the sound field and ensure the displacement accuracy. The utility model patent CN201520242815.0 relates to an acoustic power measurement device of an underwater acoustic focusing transducer. The high-precision mechanical movement device in the utility model includes an automatic movement control part of a hydrophone and a manual movement control part of a focusing transducer. The signal generator generates a pulse signal that passes through the power amplifier and then excites the focusing transducer to radiate sound waves into the water. The signal received by the hydrophone is pre-amplified and displayed by a digital oscilloscope. However, the second movement mechanism in the device is manually driven, and its precision is low. At the same time, the size of the device is small and there is no sound-absorbing layer, so the ultrasonic frequency that can be used is too limited and the measurement accuracy is low.

Acoustic quantities such as sound pressure, sound intensity, and sound power are needed in acoustic research and applications, and the most basic and widely used quantity is sound pressure. In order to detect the sound field and accurately measure the free-field sound pressure at each point in the sound field, a sound pressure measuring instrument or a standard hydrophone is required, because the sound pressure measuring instrument is usually composed of a standard hydrophone, a measuring amplifier and a filter. The key component is the standard hydrophone. However, a standard hydrophone cannot be completed only by careful design and production. It must be precisely calibrated before it can become a standard hydrophone. Therefore, the sensitivity calibration of the hydrophone occupies an important role in the acoustic measurement. Important position.

Underwater acoustic components are widely used and crucial underwater components in deep water engineering. Different application backgrounds have special requirements for the acoustic properties of materials. With the advancement of material science, new high-performance sound-absorbing materials such as viscoelastic polymer materials Materials are increasingly used in underwater acoustic engineering fields such as sound insulation and vibration reduction, sound absorption and noise reduction. Therefore, the measurement of acoustic parameters of such materials in underwater acoustic use environments has become particularly important.

Contents of the invention

The utility model patent does not solve the above problems and aims at the deficiencies of the prior art, and provides an anechoic pool for acoustic measurement.

The utility model provides the following technical solutions:

It includes a pool body 1, a sound-absorbing material layer 2, an automatic scanning device 3, an installation platform 4 and a control system 5.

The pool body 1 has a total length of 6600mm (X-axis direction), a width of 4100mm (Y-axis direction), a depth of 3500mm (Z-axis direction), a pool inner length of 5500mm, a width of 3500mm, and a depth of 3500mm. Reinforced waterproof concrete, impermeability grade S6.

The inside of the pool is equipped with steel bars with hooks, and the sound-absorbing tip is installed in the plastic shell and hung in the hook. The sound-absorbing tip shell is directly laid on the bottom of the pool, which is convenient for installation and maintenance. The thickness of the sound-absorbing material layer 2 is about 250mm .

The automatic scanning device 3 and the installation platform 4 are mechanical parts of the device.

The control system 5 adopts a six-axis servo control drive system based on an industrial computer.

The automatic scanning device 3 includes an X-direction slide rail 7 , a Y-direction slide rail 8 , a Z-direction work surface slide rail 9 and a work surface turntable 10 .

The automatic scanning device 3 is used for the scanning motion control of the hydrophone. It adopts a gantry-type four-degree-of-freedom linear module structure, which can realize the translation of the X, Y, and Z axes and the automatic rotation around the Z axis.

The automatic scanning device 3X-axis has an effective stroke of 3000mm, a precision of 0.5mm, a total length of 3500mm, a Y-axis effective stroke of 1800mm, a precision of 0.08mm, a Z-axis effective stroke of 1800mm, a precision of 0.08mm, and an effective rotation of 360° around the Z-axis, with a precision of 0.1° , 1800*1800mm local scan of the pool center is realized in the YZ section perpendicular to the horizontal direction.

The installation platform 4 includes a platform 11, a fixed surface slide rail 12 in the Z direction, and a fixed surface turntable 13. The installation platform 4 is used to install standard sound sources or calibrated transducers and arrays, and adopts two degrees of freedom of the Z axis and the rotation around the Z axis. Module structure, fixed in the directions of X and Y axes, Z-axis effective stroke 1500mm, precision 0.08mm, rotation range around Z-axis 360°, precision 0.1°, maximum load at the end of Z-axis 20Kg.

The control system 5 realizes the position servo control function by the six-axis motion control card, the servo driver and the servo motor, has strong anti-electromagnetic interference shielding measures, and realizes the fixing of the sound source or the calibrated transducer and the fixing of the hydrophone. Automatic scanning movement;

The beneficial effect of the utility model is that: the computer controls the high-precision mechanical movement device to improve the measurement accuracy, and adopts the gantry type four-degree-of-freedom linear module structure and the turntable device to ensure that the working surface of the hydrophone is parallel to the fixed surface of the material. The measurement of parameters is more precise.

Description of drawings

Fig. 1 is the schematic diagram of the structure diagram of the utility model device.

Fig. 2 is a schematic diagram of the automatic scanning device of the present invention.

Fig. 3 is a schematic diagram of the utility model and the installation platform.

Fig. 4 is a block diagram of the utility model hydrophone sensitivity calibration system.

Among the figure: 14, transducer, 15, power amplifier, 16, signal generator, 17, oscilloscope, 18, filter, 19, anechoic pool, 20, hydrophone.

specific embodiment

Below in conjunction with the practical content of the description and the description of the accompanying drawings, the specific embodiments of the utility model are described in further detail:

The signal generator 16 generates a pulse signal that passes through the power amplifier 15 and then excites the focusing transducer 14 to radiate sound waves into the water. The hydrophone 20 is installed on the working surface turntable 10 of the automatic scanning device 3, and the signal received by the hydrophone 20 passes through a filter. After 18, it is displayed by the digital oscilloscope 17; the computer controls the high-precision mechanical movement device to perform scanning measurement and collects the signal of the digital oscilloscope through serial port communication.

Further, the comparison method of hydrophone measurement is to put a hydrophone with unknown sensitivity (ie, the hydrophone to be tested) and a hydrophone with known sensitivity (ie, the standard hydrophone) into the same position in the sound field. , let them receive the same free-field sound pressure, and then compare the open-circuit output voltages of the two hydrophones. According to the definition of free-field voltage sensitivity: the two-field sound pressure p _f before and after the replacement is the same, then:

where e _x and e _s represent the open-circuit output voltages of the hydrophone to be tested and the standard hydrophone, respectively; M _x and M _s represent the free-field voltage sensitivities of the hydrophone to be tested and the standard hydrophone, respectively.

According to formula (2.1), it can be deduced that:

Namely: 20lgM _x ＝20lgM _s +20lge _x -20lge _s

Or expressed as sensitivity (level):

M _x =M _s +20lge _x -20lge _s (2.3)

From formula (2.2) or (2.3), it can be seen that as long as the open-circuit output voltages e _s and _ex of the standard hydrophones and the hydrophones to be tested are measured before and after, combined with the known standard hydrophone sensitivity M _s , the free-field voltage sensitivity M _x of the hydrophone to be tested can be obtained.

The measurement steps are as follows:

(1) Put the transmitting transducer and standard hydrophone in the proper position of the plane wave free field and fix them.

(2) Connect the instrument according to the circuit diagram and turn on the power.

(3) Adjust the output voltage of the signal source, the power amplifier, and adjust the filter to a suitable gear.

(4) Adjust the frequency values of the signal source and the filter respectively and keep them consistent, and then measure the open circuit voltage e _s of the standard hydrophone at each frequency point.

(5) Replace the standard hydrophone in the water with the hydrophone to be calibrated, and measure its open circuit output voltage e _x again, and then calculate the hydrophone to be calibrated according to the two measured data and the formula (2.2) or (2.3). The sensitivity value of the earphone at each frequency point.

Claims (3)

1. a kind of anechoic tank, for acoustic metrology, including pond body（1）, sound-absorbing material layer（2）, automatic sweep apparatus（3）、 Mounting platform（4）And control system（5）, it is characterised in that：The pond body（1）Total length 6600mm（X-direction）, width 4100mm（Y direction）, depth 3500mm（Z-direction）, length 5500mm, wide 3500mm, depth 3500mm in pond, pool wall 300 millimeters thick, pool construction uses reinforcing bar water-proof concrete, seepage-resistant grade S6；Equipped with band hook steel bar inside pond, will absorb sound Wedge is hung in plastic casing in hook, and bottom of pond is directly laid with wedge absorber shell, is easily installed and safeguards, the sound absorption Material layer（2）Thickness about 250mm；Control system（5）Using the six axis SERVO CONTROL drive systems based on industrial personal computer.

2. a kind of anechoic tank, for acoustic metrology according to claim 1, it is characterised in that：The automatically scanning dress It sets（3）Including X-direction sliding rail（7）, Y-direction sliding rail（8）, Z-direction working face sliding rail（9）With working face turntable（10）；Automatically it sweeps Imaging apparatus（3）For the scan time delay of hydrophone, using planer-type four-degree-of-freedom straight line modular structure, it can be achieved that X, Y, Z The translation of three axis and automatic rotation about the z axis；The automatic sweep apparatus（3）X-axis effective travel 3000mm, precision 0.5mm, always Long 3500mm, Y-axis effective travel 1800mm, precision 0.08mm, Z axis effective travel 1800mm, precision 0.08mm rotate about the z axis 360 ° are effectively formed, 0.1 ° of precision realizes the pond center local of 1800*1800mm in the sections YZ perpendicular to horizontal direction Scanning；Mounting platform（4）Including platform（11）, Z-direction stationary plane sliding rail（12）With stationary plane turntable（13）, mounting platform（4） For installing standard source or being calibrated energy converter, array, the two-freedom modular structure rotated using Z axis and about the z axis, X, Y Fixed in two axis directions, Z axis effective travel 1500mm, precision 0.08mm, 360 ° of rotating range, 0.1 ° of precision, Z axis are last about the z axis Hold maximum load 20Kg.

3. according to a kind of anechoic tank, for acoustic metrology described in claim 1, it is characterised in that：The control system （5）Position servo control function is realized by six axis motion control cards, servo-driver and servo motor, there is stronger anti-electromagnetism The fixation of energy converter and the automatically scanning movement of hydrophone are realized to sound source or are calibrated in interference shielding measure.