Acoustics—Measurements of the longitudinal wave velocity and attenuation coefficient for underwater acoustical materials—Pulse tube method
Some standard content:
ICS17.140
National Standard of the People's Republic of China
GB/T 5266--2006
Replaces GB/T5266-1985
Acoustics-Measurements of the longitudinal wave velocity and attenuation coefficient for underwater acoustical materials-Pulse tube method
method Issued on May 8, 2006
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China Administration of Standardization of the People's Republic of China
Implementation on November 1, 2006
Normative references
Terms and definitionsWww.bzxZ.net
Symbols and abbreviations
Measurement principle
5.1 Measurement of complex reflection coefficient
5.2 Input impedance of the sample and its relationship with the complex reflection coefficient Calculation of longitudinal wave sound velocity and attenuation coefficient
5.4 Measurement frequency range
6 Measurement device and sample
6.1 Composition of measurement device
6.2 Requirements for standard reflector
6.3 Requirements for sample
7 Measurement method
7.1 Preparation before measurement
7. 2 Measurement of complex reflection coefficient
7.3 Calculation of longitudinal wave sound velocity and attenuation coefficient
8 Measurement uncertainty·…
Appendix A (Informative Appendix) Measurement of sound velocity of water in pulse sound tube Appendix B (Informative Appendix) References
GB/T 5266--2006
This standard replaces GB/T5266--1985 "Measurement of longitudinal wave sound velocity and attenuation of underwater acoustic materials - Pulse tube method". GB/T 5266-2006
Compared with GB/T5266-1985, this standard adds digital measuring devices, uses digital program-controlled instruments and discrete Fourier transform (DFT) technology.
Appendix A and Appendix B of this standard are informative appendices. This standard was proposed by the Chinese Academy of Sciences.
This standard is under the jurisdiction of the National Technical Committee for Acoustic Standardization (SAC/TC17). The drafting units of this standard are: the 715th Institute of China Shipbuilding Industry Corporation and the Institute of Acoustics of the Chinese Academy of Sciences. The main drafters of this standard are: Li Shui, Miao Rongxing and Wang Rongjin. The previous versions of the standards replaced by this standard are: GB/T5266-1985. 1 Scope
Acoustics Measurement of longitudinal wave velocity and attenuation coefficient of underwater acoustic materials Pulse tube method
GB/T 5266-2006
This standard specifies the method of measuring the complex reflection coefficient of underwater acoustic material samples under steady-state plane wave conditions in a rigid thick-walled acoustic tube using pulse sound technology, and then calculating the longitudinal wave velocity and attenuation coefficient of the sample material. This standard is applicable to uniform and dense polymer materials for underwater acoustics. 2 Normative references
The clauses in the following documents become the clauses of this standard through reference in this standard. For all dated referenced documents, all subsequent amendments (excluding errata) or revisions are not applicable to this standard. However, parties to an agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For any undated referenced document, the latest version shall apply to this standard. GB/T3223-1994 Acoustics-Free field calibration method for underwater acoustic transducers GB/T3947-1996 Acoustics-Terminology
GB/T4472-1984 General rules for determination of density and relative density of chemical products 3 Terms and definitions
The following terms and definitions established in GB/T3947-1996 apply to this standard. 3.1
Pulse tube
A water-filled rigid thick-walled metal circular tube in which pulse sound waves can be emitted, propagated and received. Used to measure the acoustic performance parameters of underwater acoustic materials or component samples.
Note: Thick wall means that the wall thickness of the tube is not less than the inner radius of the tube. 3.2
complex reflection coefficient
The complex ratio of the reflected sound pressure to the incident sound pressure when a plane sound wave in water medium is incident on the interface (surface) of an acoustic material under given frequency and conditions.
Note: The surface should be a part of an infinite surface, and the edge effect is not included. 3.3
Longitudinal wave velocityc
The propagation speed of a longitudinal wave in an acoustic material, in meters per second (m/s). 3.4
attenuation coefficient
The number of neperts of the sound pressure amplitude attenuated per unit length of a longitudinal wave propagating in an acoustic material, in neperts per meter (Np/m). Note: 1 Np=8. 686 dB.
4 Symbols and abbreviations
The following symbols apply to this standard:
GB/T5266—2006
A.: The voltage amplitude corresponding to the reflected wave of the standard reflector received by the transducer, in volts (V). A1: The voltage amplitude corresponding to the reflected wave of the material sample received by the transducer, in volts (V). a: The inner radius of the pulse tube, in meters (m). c: The longitudinal sound velocity of the sample material, in meters per second (m/s). cw: The sound velocity in the water medium in the pulse tube, in meters per second (m/s). Cwo: The sound velocity of distilled water, in meters per second (m/s). d: The thickness of the sample, in meters (m). D: The diameter of the sample, in meters (m). D.: The inner diameter of the pulse tube, in meters (m). f: The measurement frequency, in Hertz (Hz). f.: The middle frequency of the measurement frequency range, in Hertz (Hz). fi: lower limit of measurement frequency, in Hertz (Hz). f2: upper limit of measurement frequency, in Hertz (Hz). f.: resonant frequency of transducer, in Hertz (Hz). h: wall thickness of pulse tube, in meter (m). K: number of cycles of steady-state sine wave in pulse sound wave. L: effective length of pulse tube (distance from transducer surface to sample reflection surface), in meter (m). Q: quality factor of transducer.
R: modulus of complex reflection coefficient.
t: temperature of water medium in pulse tube, in degree Celsius (℃). Zin: input acoustic impedance of sample, in Pascal second per meter (Pa·s/m). α: attenuation coefficient of sample, in neper per meter (Np/m). △l: amount of liquid level rise caused by water in the gap between sample and tube wall after sample is taken out of pulse tube, in meter (m). Ap: Phase correction of the reflected wave caused by the liquid level rise △I, in degrees (°). Φ: Phase of the complex reflection coefficient, in degrees (°). 9o: Phase of the electrical signal corresponding to the reflected wave of the standard reflector, in degrees (°). 91: Phase of the electrical signal corresponding to the reflected wave of the sample, in degrees (°). In: Wavelength of the sound wave in the sample material, in meters (m). p: Density of the sample material, in kilograms per cubic meter (kg/m). Pw: Density of the water medium in the pulse tube, in kilograms per cubic meter (kg/m). t: Pulse width, in seconds (s).
w: Angular frequency (w-2f), in radians per second (rad/s). 5 Measurement principle
5.1 Measurement of complex reflection coefficient
The sample to be tested and the standard reflector are placed alternately at one end of the pulse tube, and the rear interface impedance of the sample is known. The pulse method is used to measure the voltage amplitude and phase corresponding to the sample reflection wave and the standard reflector reflection wave received by the transducer to obtain the modulus R and phase of the complex reflection coefficient of the sample front interface9.
5.2 Input impedance of the sample and its relationship with the complex reflection coefficient When a plane wave propagates in a pulse tube, according to the acoustic transmission line theory, the input impedance of the sample can be calculated under two different backing conditions: a) When the end of the sample is an air backing (i.e., an acoustic soft end), the input acoustic impedance is calculated by formula (1): 2
tanh(ad + jw d /c)
(α+jw/c)
When the end of the sample is a rigid backing (i.e., an acoustic hard end), the input acoustic impedance is calculated by formula (2): b)
-coth(ad + jd /c)
(α+jw/c)
From the complex reflection coefficient of the front interface of the sample, the input acoustic impedance of the sample is calculated by formula (3): 1+R·eq
Za = pwcw iR.em
5.3 Calculation of longitudinal wave speed and attenuation coefficient
GB/T 5266—2006
（1）
From equations (1), (2) and (3), the relationship between the longitudinal wave speed and attenuation coefficient of the sample and the mode and phase of the complex reflection coefficient under the two terminal boundary conditions can be obtained:
a) For the acoustic soft terminal, it is expressed by equation (4): j tanh(ad + jw d /c)
ad + ja d/c
b) For the acoustic hard terminal, it is expressed by equation (5): j coth(ad + ja d/c)
ad + jw d/c
From equation (4) or (5), the longitudinal wave speed ℃ and attenuation coefficient α of the sample can be obtained. 5.4 Measurement frequency range
5.4.1 Measurement frequency upper limit
The calculation method of the pulse tube measurement frequency upper limit is as follows: 1+R·ei?
lR·ep
1+R·ejs
The measurement frequency upper limit f2 is related to the inner diameter of the tube and depends on the condition that only plane waves propagate in the pulse tube, which is expressed by formula (6): a)
When the vibration velocity distribution on the transducer surface is centrally symmetrical, the measurement frequency upper limit f2 can be increased, which is expressed by formula (7): b)
5.4.2 Measurement frequency lower limit
The calculation method of the pulse tube measurement frequency lower limit is as follows: · (4)
· (5)
...(6)
· (7)
The measurement frequency lower limit f is related to the pulse tube inner diameter. The pulse width t should be selected according to the provisions of A.2 in Appendix A of GB/T3223-1994, and should meet the conditions of formula (8): 3
GB/T5266—2006
The lower limit of the measurement frequency f is also related to the quality factor Q of the transducer, and depends on the conditions for propagating a steady-state sine wave in the pulse tube. 6)
The pulse width t should be selected according to the provisions of A.4 in Appendix A of GB/T3223--1994. If it is required that there should be at least K cycles of steady-state sine waves in the pulse sound wave, the pulse width↑ should meet the conditions of formula (9): Q+K
c) The lower limit of the measurement frequency fl is shown in formula (10): Kcwf.
fi = 2Lf.-Qcw
6 Measurement device and sample
6.1 Composition of measurement device
6.1.1 Analog measurement device
·(9)
( 10)
The composition of the analog measurement device of the pulse tube method is shown in Figure 1. This device consists of a sound tube, a transducer and an electronic measuring device. The transducer at one end of the sound tube emits a pulse-modulated sine wave into the sound tube, which is reflected by the sample at the other end of the sound tube, and then the reflected wave is received by the same transducer. By comparing the sound pressure amplitude and phase of the reflected wave of the sample with an acoustically hard (or acoustically soft) end with the reflected wave of the rigid (or flexible) standard reflector, the modulus and phase of the complex reflection coefficient of the sample are measured. Sample
Signal generator
Pulse modulator
Power amplifier
Transducer
Performance meter
Phase shifter
Amplitude indicator
Figure 1 Block diagram of pulse tube method analog measurement device
6.1.2 Digital measurement device
Transducer
Phase indicator
The composition of the digital measurement device of the pulse tube method is shown in Figure 2. The sound tube and transducer of this device are the same as those in 6.2.1. The electronic measurement equipment consists of a function generator, a power amplifier, a transceiver converter, a bandpass filter, a signal collector, and a computer system. The function generator directly generates a pulse sine signal. The bandpass filter should be able to filter out low-frequency noise and signals with a frequency higher than twice the measurement frequency. The transceiver converter should be able to close the receiving channel when the pulse signal is transmitted and open the receiving channel after the transmission. The computer is installed with measurement software, and the digital instrument is controlled through the bus to complete signal acquisition and processing, and save and print the measurement results. The measurement signal-to-noise ratio of the system should be greater than 20dB. This standard recommends digital measurement devices.
Function generator
Power amplifier
Transducer
Printer
Computer
Signal collector
Bandpass filter
Transceiver converter
Figure 2 Block diagram of pulse tube method digital measurement device
6.1.3 Pulse tube requirements
General requirements The pulse tube is a water-filled metal tube with uniform wall thickness and smooth inner wall. To ensure that the tube wall has sufficient rigidity, the ratio of the tube wall thickness h to the tube inner radius α should be greater than or equal to 1. 6.1.4 Transducer requirements
The transducer used in the pulse tube method should be a planar piston-type transducer for both transmission and reception. Under variable temperature and pressure measurement conditions, it should have good temperature stability and pressure stability. The transducer should be installed to avoid acoustic coupling with the sound tube shell. 6.1.5 Instrument requirements for analog measuring devices The instrument requirements for analog measuring devices are as follows: a) The frequency stability of the signal generator should be better than 2×10~5; the phase shifter should be able to evenly shift the phase of the sinusoidal signal within 0°~360°, with a maximum allowable error of ±2°; b) The attenuator range should be 0dB~~80dB, with a minimum step of 0.1dB; the resolution of the amplitude indicator should not be greater than 0.2dB, and the resolution of the phase indicator should not be greater than 2°; d) The maximum allowable error of the frequency meter should not be greater than ±10-4; the power amplifier should have good impedance matching with the transducer within the working frequency band, and the stability requirement is that the signal fluctuation does not exceed ±1% within 8h.
Instrument requirements for digital measuring devices
Instrument requirements for digital measuring devices are as follows:
The frequency stability of the function generator should be better than 2×10-5; a) The A/D bit number of the signal collector should be at least 8 bits, and the sampling rate should be at least 10 times greater than the maximum operating frequency of the pulse tube; b) The bandpass filter should be able to filter out low-frequency noise and signals with frequencies higher than twice the measurement frequency; d) The power amplifier should have good impedance matching with the transducer within the operating frequency band, and the stability requirement is that the signal fluctuation does not exceed ±1% within 8 hours.
6.2 Requirements for standard reflectors
6.2.1 Rigid standard reflectors can be used as total reflection references under normal pressure or pressurized conditions, and the complex reflection coefficient is approximately 1. Used for measurements under acoustic hard-end conditions. The main requirements are as follows: a) The standard reflector is usually a stainless steel cylinder, and the gap between it and the pulse tube should not be greater than 0.2mm; 5
GB/T 5266—2006
b) The length of the standard reflector should be one quarter of the wavelength of the sound wave at the frequency f. c) The applicable frequency range of the standard reflector is f0~f. 6.2.2 The flexible standard reflector can be used as a total reflection reference under normal pressure, and the complex reflection coefficient is approximately -1. It is used for measurements under acoustic soft end conditions. The flexible standard reflector is generally the air at the pipe end. Note: 6.2.2 is preferred under normal pressure.
6.3 Sample requirements
The requirements for the sample are as follows;
a) Test The sample should be made into a cylindrical shape with a cylindricality not greater than 0.1mm; the gap between the sample and the pulse tube should be not greater than 0.2mm; b) the thickness of the sample should be between 0.3 Å and 0.6 Å; the parallelism should be not greater than 0.5mm; c) the sample surface is required to be flat with a flatness not greater than 0.5mm. 7 Measurement method
7.1 Preparation before measurement
7.1.1 Preparation of pulse tube
The pulse sound tube should be prepared as follows:
a) The pulse tube should be filled with distilled water. After the first water filling or water change, it should be stable for at least 48 hours to allow sufficient infiltration between the pulse tube wall and the water medium to reach temperature equilibrium. The bubbles in the pulse tube should be removed before the measurement begins. b)
The density pw of water in the pulse tube is generally not measured. At normal pressure and water temperature t at 0℃1 Measurement frequency upper limit
The calculation method of the pulse tube measurement frequency upper limit is as follows: 1+R·ei?
lR·ep
1+R·ejs
The measurement frequency upper limit f2 is related to the inner diameter of the tube and depends on the condition that only plane waves propagate in the pulse tube, which is expressed by formula (6): a)
When the vibration velocity distribution on the transducer surface is centrally symmetrical, the measurement frequency upper limit f2 can be increased, which is expressed by formula (7): b)
5.4.2 Measurement frequency lower limit
The calculation method of the pulse tube measurement frequency lower limit is as follows: · (4)
· (5)
...(6)
· (7)
The measurement frequency lower limit f is related to the effective length of the pulse tube and should be avoided The direct and reflected pulse sound signals in the sound tube overlap and interfere with each other. The pulse width t should be selected according to the provisions of A.2 in Appendix A of GB/T3223-1994 and should meet the conditions of formula (8): 3
GB/T5266-2006
The lower limit of the measurement frequency f is also related to the quality factor Q of the transducer and depends on the conditions for propagating a steady-state sine wave in the pulse tube. 6)
The pulse width t should be selected according to the provisions of A.4 in Appendix A of GB/T3223--1994. If it is required that there should be at least K cycles of steady-state sine waves in the pulse sound wave, the pulse width↑ should meet the conditions of formula (9): Q+K
c) The lower limit of the measurement frequency fl is shown in formula (10): Kcwf.
fi = 2Lf.-Qcw
6 Measurement device and sample
6.1 Composition of measurement device
6.1.1 Analog measurement device
·(9)
( 10)
The composition of the analog measurement device of the pulse tube method is shown in Figure 1. This device consists of a sound tube, a transducer and an electronic measuring device. The transducer at one end of the sound tube emits a pulse-modulated sine wave into the sound tube, which is reflected by the sample at the other end of the sound tube, and then the reflected wave is received by the same transducer. By comparing the sound pressure amplitude and phase of the reflected wave of the sample with an acoustically hard (or acoustically soft) end with the reflected wave of the rigid (or flexible) standard reflector, the modulus and phase of the complex reflection coefficient of the sample are measured. Sample
Signal generator
Pulse modulator
Power amplifier
Transducer
Performance meter
Phase shifter
Amplitude indicator
Figure 1 Block diagram of pulse tube method analog measurement device
6.1.2 Digital measurement device
Transducer
Phase indicator
The composition of the digital measurement device of the pulse tube method is shown in Figure 2. The sound tube and transducer of this device are the same as those in 6.2.1. The electronic measurement equipment consists of a function generator, a power amplifier, a transceiver converter, a bandpass filter, a signal collector, and a computer system. The function generator directly generates a pulse sine signal. The bandpass filter should be able to filter out low-frequency noise and signals with a frequency higher than twice the measurement frequency. The transceiver converter should be able to close the receiving channel when the pulse signal is transmitted and open the receiving channel after the transmission. The computer is installed with measurement software, and the digital instrument is controlled through the bus to complete signal acquisition and processing, and save and print the measurement results. The measurement signal-to-noise ratio of the system should be greater than 20dB. This standard recommends digital measurement devices.
Function generator
Power amplifier
Transducer
Printer
Computer
Signal collector
Bandpass filter
Transceiver converter
Figure 2 Block diagram of pulse tube method digital measurement device
6.1.3 Pulse tube requirements
General requirements The pulse tube is a water-filled metal tube with uniform wall thickness and smooth inner wall. To ensure that the tube wall has sufficient rigidity, the ratio of the tube wall thickness h to the tube inner radius α should be greater than or equal to 1. 6.1.4 Transducer requirements
The transducer used in the pulse tube method should be a planar piston-type transducer for both transmission and reception. Under variable temperature and pressure measurement conditions, it should have good temperature stability and pressure stability. The transducer should be installed to avoid acoustic coupling with the sound tube shell. 6.1.5 Instrument requirements for analog measuring devices The instrument requirements for analog measuring devices are as follows: a) The frequency stability of the signal generator should be better than 2×10~5; the phase shifter should be able to evenly shift the phase of the sinusoidal signal within 0°~360°, with a maximum allowable error of ±2°; b) The attenuator range should be 0dB~~80dB, with a minimum step of 0.1dB; the resolution of the amplitude indicator should not be greater than 0.2dB, and the resolution of the phase indicator should not be greater than 2°; d) The maximum allowable error of the frequency meter should not be greater than ±10-4; the power amplifier should have good impedance matching with the transducer within the working frequency band, and the stability requirement is that the signal fluctuation does not exceed ±1% within 8h.
Instrument requirements for digital measuring devices
Instrument requirements for digital measuring devices are as follows:
The frequency stability of the function generator should be better than 2×10-5; a) The A/D bit number of the signal collector should be at least 8 bits, and the sampling rate should be at least 10 times greater than the maximum operating frequency of the pulse tube; b) The bandpass filter should be able to filter out low-frequency noise and signals with frequencies higher than twice the measurement frequency; d) The power amplifier should have good impedance matching with the transducer within the operating frequency band, and the stability requirement is that the signal fluctuation does not exceed ±1% within 8 hours.
6.2 Requirements for standard reflectors
6.2.1 Rigid standard reflectors can be used as total reflection references under normal pressure or pressurized conditions, and the complex reflection coefficient is approximately 1. Used for measurements under acoustic hard-end conditions. The main requirements are as follows: a) The standard reflector is usually a stainless steel cylinder, and the gap between it and the pulse tube should not be greater than 0.2mm; 5
GB/T 5266—2006
b) The length of the standard reflector should be one quarter of the wavelength of the sound wave at the frequency f. c) The applicable frequency range of the standard reflector is f0~f. 6.2.2 The flexible standard reflector can be used as a total reflection reference under normal pressure, and the complex reflection coefficient is approximately -1. It is used for measurements under acoustic soft end conditions. The flexible standard reflector is generally the air at the pipe end. Note: 6.2.2 is preferred under normal pressure.
6.3 Sample requirements
The requirements for the sample are as follows;
a) Test The sample should be made into a cylindrical shape with a cylindricality not greater than 0.1mm; the gap between the sample and the pulse tube should be not greater than 0.2mm; b) the thickness of the sample should be between 0.3 Å and 0.6 Å; the parallelism should be not greater than 0.5mm; c) the sample surface is required to be flat with a flatness not greater than 0.5mm. 7 Measurement method
7.1 Preparation before measurement
7.1.1 Preparation of pulse tube
The pulse sound tube should be prepared as follows:
a) The pulse tube should be filled with distilled water. After the first water filling or water change, it should be stable for at least 48 hours to allow sufficient infiltration between the pulse tube wall and the water medium to reach temperature equilibrium. The bubbles in the pulse tube should be removed before the measurement begins. b)
The density pw of water in the pulse tube is generally not measured. At normal pressure and water temperature t at 0℃1 Measurement frequency upper limit
The calculation method of the pulse tube measurement frequency upper limit is as follows: 1+R·ei?
lR·ep
1+R·ejs
The measurement frequency upper limit f2 is related to the inner diameter of the tube and depends on the condition that only plane waves propagate in the pulse tube, which is expressed by formula (6): a)
When the vibration velocity distribution on the transducer surface is centrally symmetrical, the measurement frequency upper limit f2 can be increased, which is expressed by formula (7): b)
5.4.2 Measurement frequency lower limit
The calculation method of the pulse tube measurement frequency lower limit is as follows: · (4)
· (5)
...(6)
· (7)
The measurement frequency lower limit f is related to the effective length of the pulse tube and should be avoided The direct and reflected pulse sound signals in the sound tube overlap and interfere with each other. The pulse width t should be selected according to the provisions of A.2 in Appendix A of GB/T3223-1994 and should meet the conditions of formula (8): 3
GB/T5266-2006
The lower limit of the measurement frequency f is also related to the quality factor Q of the transducer and depends on the conditions for propagating a steady-state sine wave in the pulse tube. 6)
The pulse width t should be selected according to the provisions of A.4 in Appendix A of GB/T3223--1994. If it is required that there should be at least K cycles of steady-state sine waves in the pulse sound wave, the pulse width↑ should meet the conditions of formula (9): Q+K
c) The lower limit of the measurement frequency fl is shown in formula (10): Kcwf.
fi = 2Lf.-Qcw
6 Measurement device and sample
6.1 Composition of measurement device
6.1.1 Analog measurement device
·(9)
( 10)
The composition of the analog measurement device of the pulse tube method is shown in Figure 1. This device consists of a sound tube, a transducer and an electronic measuring device. The transducer at one end of the sound tube emits a pulse-modulated sine wave into the sound tube, which is reflected by the sample at the other end of the sound tube, and then the reflected wave is received by the same transducer. By comparing the sound pressure amplitude and phase of the reflected wave of the sample with an acoustically hard (or acoustically soft) end with the reflected wave of the rigid (or flexible) standard reflector, the modulus and phase of the complex reflection coefficient of the sample are measured. Sample
Signal generator
Pulse modulator
Power amplifier
Transducer
Performance meter
Phase shifter
Amplitude indicator
Figure 1 Block diagram of pulse tube method analog measurement device
6.1.2 Digital measurement device
Transducer
Phase indicator
The composition of the digital measurement device of the pulse tube method is shown in Figure 2. The sound tube and transducer of this device are the same as those in 6.2.1. The electronic measurement equipment consists of a function generator, a power amplifier, a transceiver converter, a bandpass filter, a signal collector, and a computer system. The function generator directly generates a pulse sine signal. The bandpass filter should be able to filter out low-frequency noise and signals with a frequency higher than twice the measurement frequency. The transceiver converter should be able to close the receiving channel when the pulse signal is transmitted and open the receiving channel after the transmission. The computer is installed with measurement software, and the digital instrument is controlled through the bus to complete signal acquisition and processing, and save and print the measurement results. The measurement signal-to-noise ratio of the system should be greater than 20dB. This standard recommends digital measurement devices.
Function generator
Power amplifier
Transducer
Printer
Computer
Signal collector
Bandpass filter
Transceiver converter
Figure 2 Block diagram of pulse tube method digital measurement device
6.1.3 Pulse tube requirements
General requirements The pulse tube is a water-filled metal tube with uniform wall thickness and smooth inner wall. To ensure that the tube wall has sufficient rigidity, the ratio of the tube wall thickness h to the tube inner radius α should be greater than or equal to 1. 6.1.4 Transducer requirements
The transducer used in the pulse tube method should be a planar piston-type transducer for both transmission and reception. Under variable temperature and pressure measurement conditions, it should have good temperature stability and pressure stability. The transducer should be installed to avoid acoustic coupling with the sound tube shell. 6.1.5 Instrument requirements for analog measuring devices The instrument requirements for analog measuring devices are as follows: a) The frequency stability of the signal generator should be better than 2×10~5; the phase shifter should be able to evenly shift the phase of the sinusoidal signal within 0°~360°, with a maximum allowable error of ±2°; b) The attenuator range should be 0dB~~80dB, with a minimum step of 0.1dB; the resolution of the amplitude indicator should not be greater than 0.2dB, and the resolution of the phase indicator should not be greater than 2°; d) The maximum allowable error of the frequency meter should not be greater than ±10-4; the power amplifier should have good impedance matching with the transducer within the working frequency band, and the stability requirement is that the signal fluctuation does not exceed ±1% within 8h.
Instrument requirements for digital measuring devices
Instrument requirements for digital measuring devices are as follows:
The frequency stability of the function generator should be better than 2×10-5; a) The A/D bit number of the signal collector should be at least 8 bits, and the sampling rate should be at least 10 times greater than the maximum operating frequency of the pulse tube; b) The bandpass filter should be able to filter out low-frequency noise and signals with frequencies higher than twice the measurement frequency; d) The power amplifier should have good impedance matching with the transducer within the operating frequency band, and the stability requirement is that the signal fluctuation does not exceed ±1% within 8 hours.
6.2 Requirements for standard reflectors
6.2.1 Rigid standard reflectors can be used as total reflection references under normal pressure or pressurized conditions, and the complex reflection coefficient is approximately 1. Used for measurements under acoustic hard-end conditions. The main requirements are as follows: a) The standard reflector is usually a stainless steel cylinder, and the gap between it and the pulse tube should not be greater than 0.2mm; 5
GB/T 5266—2006
b) The length of the standard reflector should be one quarter of the wavelength of the sound wave at the frequency f. c) The applicable frequency range of the standard reflector is f0~f. 6.2.2 The flexible standard reflector can be used as a total reflection reference under normal pressure, and the complex reflection coefficient is approximately -1. It is used for measurements under acoustic soft end conditions. The flexible standard reflector is generally the air at the pipe end. Note: 6.2.2 is preferred under normal pressure.
6.3 Sample requirements
The requirements for the sample are as follows;
a) Test The sample should be made into a cylindrical shape with a cylindricality not greater than 0.1mm; the gap between the sample and the pulse tube should be not greater than 0.2mm; b) the thickness of the sample should be between 0.3 Å and 0.6 Å; the parallelism should be not greater than 0.5mm; c) the sample surface is required to be flat with a flatness not greater than 0.5mm. 7 Measurement method
7.1 Preparation before measurement
7.1.1 Preparation of pulse tube
The pulse sound tube should be prepared as follows:
a) The pulse tube should be filled with distilled water. After the first water filling or water change, it should be stable for at least 48 hours to allow sufficient infiltration between the pulse tube wall and the water medium to reach temperature equilibrium. The bubbles in the pulse tube should be removed before the measurement begins. b)
The density pw of water in the pulse tube is generally not measured. At normal pressure and water temperature t at 0℃1 Analog measurement device
·（9）
（ 10)
The analog measurement device of the pulse tube method is shown in Figure 1. This device consists of a sound tube, a transducer and an electronic measuring device. The transducer at one end of the sound tube emits a pulse-modulated sine wave into the sound tube, which is reflected by the sample at the other end of the sound tube, and then the reflected wave is received by the same transducer. By comparing the sound pressure amplitude and phase of the reflected wave of the sample with an acoustically hard (or acoustically soft) end with the reflected wave of the rigid (or flexible) standard reflector, the amplitude and phase of the complex reflection coefficient of the sample are measured. Sample
Signal generator
Pulse modulator
Power amplifier
Transducer
Performance meter
Phase shifter
Amplitude indicator
Figure 1 Block diagram of pulse tube method analog measurement device
6.1.2 Digital measurement device
Transducer
Phase indicator
The composition of the digital measurement device of the pulse tube method is shown in Figure 2. The sound tube and transducer of this device are the same as those in 6.2.1. The electronic measurement equipment consists of a function generator, a power amplifier, a transceiver converter, a bandpass filter, a signal collector, and a computer system. The function generator directly generates a pulse sine signal. The bandpass filter should be able to filter out low-frequency noise and signals with a frequency higher than twice the measurement frequency. The transceiver converter should be able to close the receiving channel when the pulse signal is transmitted and open the receiving channel after the transmission. The computer is installed with measurement software, and the digital instrument is controlled through the bus to complete signal acquisition and processing, and save and print the measurement results. The measurement signal-to-noise ratio of the system should be greater than 20dB. This standard recommends digital measurement devices.
Function generator
Power amplifier
Transducer
Printer
Computer
Signal collector
Bandpass filter
Transceiver converter
Figure 2 Block diagram of pulse tube method digital measurement device
6.1.3 Pulse tube requirements
General requirements The pulse tube is a water-filled metal tube with uniform wall thickness and smooth inner wall. To ensure that the tube wall has sufficient rigidity, the ratio of the tube wall thickness h to the tube inner radius α should be greater than or equal to 1. 6.1.4 Transducer requirements
The transducer used in the pulse tube method should be a planar piston-type transducer for both transmission and reception. Under variable temperature and pressure measurement conditions, it should have good temperature stability and pressure stability. The transducer should be installed to avoid acoustic coupling with the sound tube shell. 6.1.5 Instrument requirements for analog measuring devices The instrument requirements for analog measuring devices are as follows: a) The frequency stability of the signal generator should be better than 2×10~5; the phase shifter should be able to evenly shift the phase of the sinusoidal signal within 0°~360°, with a maximum allowable error of ±2°; b) The attenuator range should be 0dB~~80dB, with a minimum step of 0.1dB; the resolution of the amplitude indicator should not be greater than 0.2dB, and the resolution of the phase indicator should not be greater than 2°; d) The maximum allowable error of the frequency meter should not be greater than ±10-4; the power amplifier should have good impedance matching with the transducer within the working frequency band, and the stability requirement is that the signal fluctuation does not exceed ±1% within 8h.
Instrument requirements for digital measuring devices
Instrument requirements for digital measuring devices are as follows:
The frequency stability of the function generator should be better than 2×10-5; a) The A/D bit number of the signal collector should be at least 8 bits, and the sampling rate should be at least 10 times greater than the maximum operating frequency of the pulse tube; b) The bandpass filter should be able to filter out low-frequency noise and signals with frequencies higher than twice the measurement frequency; d) The power amplifier should have good impedance matching with the transducer within the operating frequency band, and the stability requirement is that the signal fluctuation does not exceed ±1% within 8 hours.
6.2 Requirements for standard reflectors
6.2.1 Rigid standard reflectors can be used as total reflection references under normal pressure or pressurized conditions, and the complex reflection coefficient is approximately 1. Used for measurements under acoustic hard-end conditions. The main requirements are as follows: a) The standard reflector is usually a stainless steel cylinder, and the gap between it and the pulse tube should not be greater than 0.2mm; 5
GB/T 5266—2006
b) The length of the standard reflector should be one quarter of the wavelength of the sound wave at the frequency f. c) The applicable frequency range of the standard reflector is f0~f. 6.2.2 The flexible standard reflector can be used as a total reflection reference under normal pressure, and the complex reflection coefficient is approximately -1. It is used for measurements under acoustic soft end conditions. The flexible standard reflector is generally the air at the pipe end. Note: 6.2.2 is preferred under normal pressure.
6.3 Sample requirements
The requirements for the sample are as follows;
a) Test The sample should be made into a cylindrical shape with a cylindricality not greater than 0.1mm; the gap between the sample and the pulse tube should be not greater than 0.2mm; b) the thickness of the sample should be between 0.3 Å and 0.6 Å; the parallelism should be not greater than 0.5mm; c) the sample surface is required to be flat with a flatness not greater than 0.5mm. 7 Measurement method
7.1 Preparation before measurement
7.1.1 Preparation of pulse tube
The pulse sound tube should be prepared as follows:
a) The pulse tube should be filled with distilled water. After the first water filling or water change, it should be stable for at least 48 hours to allow sufficient infiltration between the pulse tube wall and the water medium to reach temperature equilibrium. The bubbles in the pulse tube should be removed before the measurement begins. b)
The density pw of water in the pulse tube is generally not measured. At normal pressure and water temperature t at 0℃1 Analog measurement device
·（9）
（ 10)
The analog measurement device of the pulse tube method is shown in Figure 1. This device consists of a sound tube, a transducer and an electronic measuring device. The transducer at one end of the sound tube emits a pulse-modulated sine wave into the sound tube, which is reflected by the sample at the other end of the sound tube, and then the reflected wave is received by the same transducer. By comparing the sound pressure amplitude and phase of the reflected wave of the sample with an acoustically hard (or acoustically soft) end with the reflected wave of the rigid (or flexible) standard reflector, the amplitude and phase of the complex reflection coefficient of the sample are measured. Sample
Signal generator
Pulse modulator
Power amplifier
Transducer
Performance meter
Phase shifter
Amplitude indicator
Figure 1 Block diagram of pulse tube method analog measurement device
6.1.2 Digital measurement device
Transducer
Phase indicator
The composition of the digital measurement device of the pulse tube method is shown in Figure 2. The sound tube and transducer of this device are the same as those in 6.2.1. The electronic measurement equipment consists of a function generator, a power amplifier, a transceiver converter, a bandpass filter, a signal collector, and a computer system. The function generator directly generates a pulse sine signal. The bandpass filter should be able to filter out low-frequency noise and signals with a frequency higher than twice the measurement frequency. The transceiver converter should be able to close the receiving channel when the pulse signal is transmitted and open the receiving channel after the transmission. The computer is installed with measurement software, and the digital instrument is controlled through the bus to complete signal acquisition and processing, and save and print the measurement results. The measurement signal-to-noise ratio of the system should be greater than 20dB. This standard recommends digital measurement devices.
Function generator
Power amplifier
Transducer
Printer
Computer
Signal collector
Bandpass filter
Transceiver converter
Figure 2 Block diagram of pulse tube method digital measurement device
6.1.3 Pulse tube requirements
General requirements The pulse tube is a water-filled metal tube with uniform wall thickness and smooth inner wall. To ensure that the tube wall has sufficient rigidity, the ratio of the tube wall thickness h to the tube inner radius α should be greater than or equal to 1. 6.1.4 Transducer requirements
The transducer used in the pulse tube method should be a planar piston-type transducer for both transmission and reception. Under variable temperature and pressure measurement conditions, it should have good temperature stability and pressure stability. The transducer should be installed to avoid acoustic coupling with the sound tube shell. 6.1.5 Instrument requirements for analog measuring devices The instrument requirements for analog measuring devices are as follows: a) The frequency stability of the signal generator should be better than 2×10~5; the phase shifter should be able to evenly shift the phase of the sinusoidal signal within 0°~360°, with a maximum allowable error of ±2°; b) The attenuator range should be 0dB~~80dB, with a minimum step of 0.1dB; the resolution of the amplitude indicator should not be greater than 0.2dB, and the resolution of the phase indicator should not be greater than 2°; d) The maximum allowable error of the frequency meter should not be greater than ±10-4; the power amplifier should have good impedance matching with the transducer within the working frequency band, and the stability requirement is that the signal fluctuation does not exceed ±1% within 8h.
Instrument requirements for digital measuring devices
Instrument requirements for digital measuring devices are as follows:
The frequency stability of the function generator should be better than 2×10-5; a) The A/D bit number of the signal collector should be at least 8 bits, and the sampling rate should be at least 10 times greater than the maximum operating frequency of the pulse tube; b) The bandpass filter should be able to filter out low-frequency noise and signals with frequencies higher than twice the measurement frequency; d) The power amplifier should have good impedance matching with the transducer within the operating frequency band, and the stability requirement is that the signal fluctuation does not exceed ±1% within 8 hours.
6.2 Requirements for standard reflectors
6.2.1 Rigid standard reflectors can be used as total reflection references under normal pressure or pressurized conditions, and the complex reflection coefficient is approximately 1. Used for measurements under acoustic hard-end conditions. The main requirements are as follows: a) The standard reflector is usually a stainless steel cylinder, and the gap between it and the pulse tube should not be greater than 0.2mm; 5
GB/T 5266—2006
b) The length of the standard reflector should be one quarter of the wavelength of the sound wave at the frequency f. c) The applicable frequency range of the standard reflector is f0~f. 6.2.2 The flexible standard reflector can be used as a total reflection reference under normal pressure, and the complex reflection coefficient is approximately -1. It is used for measurements under acoustic soft end conditions. The flexible standard reflector is generally the air at the pipe end. Note: 6.2.2 is preferred under normal pressure.
6.3 Sample requirements
The requirements for the sample are as follows;
a) Test The sample should be made into a cylindrical shape with a cylindricality not greater than 0.1mm; the gap between the sample and the pulse tube should be not greater than 0.2mm; b) the thickness of the sample should be between 0.3 Å and 0.6 Å; the parallelism should be not greater than 0.5mm; c) the sample surface is required to be flat with a flatness not greater than 0.5mm. 7 Measurement method
7.1 Preparation before measurement
7.1.1 Preparation of pulse tube
The pulse sound tube should be prepared as follows:
a) The pulse tube should be filled with distilled water. After the first water filling or water change, it should be stable for at least 48 hours to allow sufficient infiltration between the pulse tube wall and the water medium to reach temperature equilibrium. The bubbles in the pulse tube should be removed before the measurement begins. b)
The density pw of water in the pulse tube is generally not measured. At normal pressure and water temperature t at 0℃2dB, the resolution of the phase indicator should not be greater than 2°d)
the maximum allowable error of the frequency meter should not be greater than ±10-4; the power amplifier should have good impedance matching with the transducer within the working frequency band, and the stability requirement is that the signal fluctuation does not exceed ±1% within 8h.
Instrument requirements for digital measuring devices
Instrument requirements for digital measuring devices are as follows:
The frequency stability of the function generator should be better than 2×10-5; a) The A/D bit number of the signal collector should be at least 8 bits, and the sampling rate should be at least 10 times greater than the maximum operating frequency of the pulse tube; b) The bandpass filter should be able to filter out low-frequency noise and signals with frequencies higher than twice the measurement frequency; d) The power amplifier should have good impedance matching with the transducer within the operating frequency band, and the stability requirement is that the signal fluctuation does not exceed ±1% within 8 hours.
6.2 Requirements for standard reflectors
6.2.1 Rigid standard reflectors can be used as total reflection references under normal pressure or pressurized conditions, and the complex reflection coefficient is approximately 1. Used for measurements under acoustic hard-end conditions. The main requirements are as follows: a) The standard reflector is usually a stainless steel cylinder, and the gap between it and the pulse tube should not be greater than 0.2mm; 5
GB/T 5266—2006
b) The length of the standard reflector should be one quarter of the wavelength of the sound wave at the frequency f. c) The applicable frequency range of the standard reflector is f0~f. 6.2.2 The flexible standard reflector can be used as a total reflection reference under normal pressure, and the complex reflection coefficient is approximately -1. It is used for measurements under acoustic soft end conditions. The flexible standard reflector is generally the air at the pipe end. Note: 6.2.2 is preferred under normal pressure.
6.3 Sample requirements
The requirements for the sample are as follows;
a) Test The sample should be made into a cylindrical shape with a cylindricality not greater than 0.1mm; the gap between the sample and the pulse tube should be not greater than 0.2mm; b) the thickness of the sample should be between 0.3 Å and 0.6 Å; the parallelism should be not greater than 0.5mm; c) the sample surface is required to be flat with a flatness not greater than 0.5mm. 7 Measurement method
7.1 Preparation before measurement
7.1.1 Preparation of pulse tube
The pulse sound tube should be prepared as follows:
a) The pulse tube should be filled with distilled water. After the first water filling or water change, it should be stable for at least 48 hours to allow sufficient infiltration between the pulse tube wall and the water medium to reach temperature equilibrium. The bubbles in the pulse tube should be removed before the measurement begins. b)
The density pw of water in the pulse tube is generally not measured. At normal pressure and water temperature t at 0℃2dB, the resolution of the phase indicator should not be greater than 2°d)
the maximum allowable error of the frequency meter should not be greater than ±10-4; the power amplifier should have good impedance matching with the transducer within the working frequency band, and the stability requirement is that the signal fluctuation does not exceed ±1% within 8h.
Instrument requirements for digital measuring devices
Instrument requirements for digital measuring devices are as follows:
The frequency stability of the function generator should be better than 2×10-5; a) The A/D bit number of the signal collector should be at least 8 bits, and the sampling rate should be at least 10 times greater than the maximum operating frequency of the pulse tube; b) The bandpass filter should be able to filter out low-frequency noise and signals with frequencies higher than twice the measurement frequency; d) The power amplifier should have good impedance matching with the transducer within the operating frequency band, and the stability requirement is that the signal fluctuation does not exceed ±1% within 8 hours.
6.2 Requirements for standard reflectors
6.2.1 Rigid standard reflectors can be used as total reflection references under normal pressure or pressurized conditions, and the complex reflection coefficient is approximately 1. Used for measurements under acoustic hard-end conditions. The main requirements are as follows: a) The standard reflector is usually a stainless steel cylinder, and the gap between it and the pulse tube should not be greater than 0.2mm; 5
GB/T 5266—2006
b) The length of the standard reflector should be one quarter of the wavelength of the sound wave at the frequency f. c) The applicable frequency range of the standard reflector is f0~f. 6.2.2 The flexible standard reflector can be used as a total reflection reference under normal pressure, and the complex reflection coefficient is approximately -1. It is used for measurements under acoustic soft end conditions. The flexible standard reflector is generally the air at the pipe end. Note: 6.2.2 is preferred under normal pressure.
6.3 Sample requirements
The requirements for the sample are as follows;
a) Test The sample should be made into a cylindrical shape with a cylindricality not greater than 0.1mm; the gap between the sample and the pulse tube should be not greater than 0.2mm; b) the thickness of the sample should be between 0.3 Å and 0.6 Å; the parallelism should be not greater than 0.5mm; c) the sample surface is required to be flat with a flatness not greater than 0.5mm. 7 Measurement method
7.1 Preparation before measurement
7.1.1 Preparation of pulse tube
The pulse sound tube should be prepared as follows:
a) The pulse tube should be filled with distilled water. After the first water filling or water change, it should be stable for at least 48 hours to allow sufficient infiltration between the pulse tube wall and the water medium to reach temperature equilibrium. The bubbles in the pulse tube should be removed before the measurement begins. b)
The density pw of water in the pulse tube is generally not measured. At normal pressure and water temperature t at 0℃
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