A method and system for measuring equivalent acoustic parameters of soft ultrasonic gel material

Abstract

The present invention discloses a method and system for determining equivalent acoustic parameters of a soft ultrasonic gel material. The method comprises: measuring the reflection coefficient of a soft gel metamaterial-backing plate structure; measuring the transmission coefficient of a soft gel metamaterial-backing plate structure; determining the impedance of the soft gel metamaterial according to the reflection coefficient and the transmission coefficient; determining the phase change of the sound wave in the soft gel metamaterial based on the impedance of the soft gel metamaterial; calculating the sound velocity in the soft gel metamaterial according to the phase change of the sound wave in the soft gel metamaterial; calculating the equivalent acoustic parameters of the soft ultrasonic gel material according to the impedance of the soft gel metamaterial and the sound velocity in the soft gel metamaterial; the equivalent acoustic parameters include equivalent elastic modulus and equivalent mass density. The present invention can indirectly determine the equivalent mass density and equivalent elastic modulus parameters of the acoustic metamaterial by adding a backing material behind the soft gel metamaterial.

Description

Technical Field

[0001] The present invention relates to the technical field of acoustic metamaterials, and in particular to a method and system for determining equivalent acoustic parameters of a soft ultrasonic gel material. Background Art

[0002] Acoustic metamaterials are artificial structural materials. Through artificial design of the material structure, the material as a whole behaves as a material with unique acoustic properties, such as negative refraction, acoustic invisibility, extraordinary transmission, sub-wavelength imaging, etc. By designing soft gel ultrasound metamaterials, it is possible to enhance the energy of ultrasound penetrating the skull, but in actual measurements, the reflection signal of this soft gel metamaterial is too weak to be measured. Summary of the invention

[0003] The purpose of the present invention is to provide a method and system for determining equivalent acoustic parameters of a soft ultrasonic gel material, by adding a backing material behind the soft gel metamaterial, to indirectly determine the equivalent mass density and equivalent elastic modulus parameters of the acoustic metamaterial.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] A method for determining equivalent acoustic parameters of a soft ultrasonic gel material, comprising:

[0006] Measuring the reflection coefficient of a soft gel metamaterial-backing plate structure; the soft gel metamaterial-backing plate structure is composed of a backing plate placed behind the soft gel metamaterial;

[0007] Measuring the transmission coefficient of the soft gel metamaterial-backing plate structure;

[0008] Determining the impedance of the soft gel metamaterial according to the reflection coefficient and the transmission coefficient;

[0009] determining a phase change of an acoustic wave in the soft gel metamaterial based on the impedance of the soft gel metamaterial;

[0010] Calculating the speed of sound in the soft gel metamaterial according to the phase change of the sound wave in the soft gel metamaterial;

[0011] According to the impedance of the soft gel metamaterial and the sound velocity in the soft gel metamaterial, the equivalent acoustic parameters of the soft ultrasound gel material are calculated; the equivalent acoustic parameters include an equivalent elastic modulus and an equivalent mass density.

[0012] Optionally, measuring the reflection coefficient of the soft gel metamaterial-backing plate structure specifically includes:

[0013] Measuring the direct signal from the transducer and the reflected signal reflected by the soft gel metamaterial-backing plate structure by a hydrophone;

[0014] The reflection coefficient of the soft gel metamaterial-backing plate structure is obtained by Fourier transforming the reflected signal and the direct signal and dividing them.

[0015] Optionally, measuring the transmission coefficient of the soft gel metamaterial-backing plate structure specifically includes:

[0016] Measuring the direct signal from the transducer and the transmitted signal through the soft gel metamaterial-backing plate structure by a hydrophone;

[0017] The transmission signal and the direct signal are Fourier transformed and then divided to obtain the transmission coefficient of the soft gel metamaterial-backing plate structure.

[0018] Optionally, the calculation formula of the equivalent acoustic parameters of the soft ultrasound gel material is as follows:

[0019]

[0020] Among them, ρ eff is the equivalent mass density, K eff is the equivalent elastic modulus, Z3 is the impedance of the soft gel metamaterial, c3 is the sound velocity in the soft gel metamaterial, ρ3=ρ eff , ρ3 is the mass density of the soft gel metamaterial.

[0021] Optionally, the calculation formula of the phase change φ3 of the sound wave in the soft gel metamaterial is as follows:

[0022]

[0023] Wherein, f is the test frequency of the transducer, d3 is the thickness of the soft gel metamaterial, θ3 is the incident angle of the sound wave from the soft gel metamaterial to the backing plate, and c3 is the phase change of the sound wave in the soft gel metamaterial.

[0024] The present invention also provides a system for measuring equivalent acoustic parameters of soft ultrasonic gel materials, comprising:

[0025] A reflection coefficient measurement module, used to measure the reflection coefficient of a soft gel metamaterial-backing plate structure; the soft gel metamaterial-backing plate structure is composed of a backing plate placed behind the soft gel metamaterial;

[0026] A transmission coefficient measurement module, used to measure the transmission coefficient of the soft gel metamaterial-backing plate structure;

[0027] A soft gel metamaterial impedance determination module, used to determine the impedance of the soft gel metamaterial according to the reflection coefficient and the transmission coefficient;

[0028] a phase change determination module, configured to determine a phase change of an acoustic wave in the soft gel metamaterial based on the impedance of the soft gel metamaterial;

[0029] A sound velocity calculation module, used for calculating the sound velocity in the soft gel metamaterial according to the phase change of the sound wave in the soft gel metamaterial;

[0030] An equivalent acoustic parameter calculation module is used to calculate the equivalent acoustic parameters of the soft ultrasound gel material according to the impedance of the soft gel metamaterial and the sound velocity in the soft gel metamaterial; the equivalent acoustic parameters include an equivalent elastic modulus and an equivalent mass density.

[0031] Optionally, the calculation formula of the equivalent acoustic parameters of the soft ultrasound gel material is as follows:

[0032]

[0033] Among them, ρ eff is the equivalent mass density, K eff is the equivalent elastic modulus, Z3 is the impedance of the soft gel metamaterial, c3 is the sound velocity in the soft gel metamaterial, ρ3=ρ eff , ρ3 is the mass density of the soft gel metamaterial.

[0034] Optionally, the calculation formula of the phase change φ3 of the sound wave in the soft gel metamaterial is as follows:

[0035]

[0036] Wherein, f is the test frequency of the transducer, d3 is the thickness of the soft gel metamaterial, θ3 is the incident angle of the sound wave from the soft gel metamaterial to the backing plate, and c3 is the phase change of the sound wave in the soft gel metamaterial.

[0037] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0038] The measurement of the reflected signal is particularly important in the calculation of the equivalent acoustic parameters (equivalent mass density and equivalent elastic modulus) of the soft gel metamaterial. The present invention solves the problem that the reflected signal of the soft gel metamaterial is too weak to be measured by adding a backing material behind the soft gel metamaterial. Further, by measuring the reflected signal and the transmitted signal of the soft gel metamaterial-backing plate structure, according to the propagation theory of sound waves in any multilayer medium, the equivalent acoustic parameters (equivalent mass density and equivalent elastic modulus) of the soft gel metamaterial to be measured are calculated. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0040] Figure 1 A flow chart of a method for determining equivalent acoustic parameters of a soft ultrasound gel material provided by the present invention;

[0041] Figure 2 A schematic diagram of the structure of the soft gel metamaterial-backing plate provided by the present invention;

[0042] Figure 3 A schematic diagram of the reflection coefficient measurement of the soft gel metamaterial-backing plate structure provided by the present invention;

[0043] Figure 4 Schematic diagram of the transmission coefficient measurement of the soft gel metamaterial-backing plate structure provided by the present invention. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] The purpose of the present invention is to provide a method and system for determining equivalent acoustic parameters of a soft ultrasonic gel material, by adding a backing material behind the soft gel metamaterial, to indirectly determine the equivalent mass density and equivalent elastic modulus parameters of the acoustic metamaterial.

[0046] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] like Figure 1 As shown, the method for determining equivalent acoustic parameters of a soft ultrasound gel material provided by the present invention comprises the following steps:

[0048] Step 101: Measure the reflection coefficient of a soft gel metamaterial-backing plate structure; the soft gel metamaterial-backing plate structure is composed of a backing plate placed behind the soft gel metamaterial.

[0049] Step 102: Measure the transmission coefficient of the soft gel metamaterial-backing plate structure.

[0050] Step 103: Determine the impedance of the soft gel metamaterial according to the reflection coefficient and the transmission coefficient.

[0051] Step 104: Determine a phase change of an acoustic wave in the soft gel metamaterial based on the impedance of the soft gel metamaterial.

[0052] Step 105: Calculate the speed of sound in the soft gel metamaterial according to the phase change of the sound wave in the soft gel metamaterial.

[0053] Step 106: Calculate equivalent acoustic parameters of the soft ultrasound gel material according to the impedance of the soft gel metamaterial and the sound velocity in the soft gel metamaterial; the equivalent acoustic parameters include an equivalent elastic modulus and an equivalent mass density.

[0054] The principle of the above method provided by the present invention is as follows:

[0055] Step 1: Calculation of equivalent acoustic parameters of soft gel metamaterials

[0056] A backing plate is placed behind the soft gel metamaterial to form a soft gel metamaterial-backing plate structure, such as Figure 2 shown.

[0057] Among them, medium 1 and 4 are degassed, medium 2 is a backing material with known impedance and sound velocity (the reflection signal and transmission signal of this material are easy to observe), and medium 3 is the soft gel metamaterial to be tested. The sound wave enters medium 3 from medium 4 at a certain angle θ4, and then exits from medium 2 to medium 1 at a certain angle θ1. At this time, the transmission coefficient is determined by formula (1):

[0058]

[0059] Expanding formula (1) yields:

[0060]

[0061] in is the "input impedance" when the sound wave enters medium j from medium j+1, and Determined by formulas (3) and (4) respectively:

[0062]

[0063]

[0064] Where Z j =ρ jc j / cosθ j is the impedance in each medium, ρ j is the density of each medium, The phase change of sound waves in various media The tangent value of .

[0065] In addition, the reflection coefficient of the multilayer medium is determined by formula (5):

[0066]

[0067] Substituting formula (4) into formula (5) and combining it with formula (2), we get:

[0068]

[0069] in:

[0070]

[0071] B=-(Z1p2+iZ2) (8)

[0072]

[0073]

[0074]

[0075]

[0076]

[0077] In formula (6), there are Z3, p3 and Three unknown quantities. According to Euler's formula, p3 and The following relationship exists:

[0078]

[0079] Substituting formula (14) into formula (6), we get the equation for Z3 as follows:

[0080] M·Z3 4 +N·Z3 3 +O·Z3 2 +P·Z3+Q=0 (15)

[0081] in:

[0082] M=B(F 2 -E 2 ) (16)

[0083] N=2B(FG-DE)-Ai(F 2 +E 2 ) (17)

[0084] O=B(G 2 -D 2 )+C(F 2 -E 2 )-2Ai(FG+DE) (18)

[0085] P=2C(FG-DE)-Ai(G 2 +D 2 ) (19)

[0086] Q=C(G 2 -D 2 ) (20)

[0087] Solving equation (15), we can get Z3 and calculate the corresponding

[0088] The phase change The expression is as follows:

[0089]

[0090] The sound velocity in medium 3 (the soft gel metamaterial to be tested) is deduced from this:

[0091]

[0092] Finally, the equivalent mass density ρ of the soft gel metamaterial is derived from Z3 and c3 eff and equivalent elastic modulus K eff :

[0093]

[0094] ρ3=ρ eff

[0095] From the above theoretical derivation, it can be observed that when the reflection coefficient of the sound wave on the incident surface (to be measured), the transmission coefficient on the exit surface (to be measured) and the relevant acoustic parameters of the backing material (known) are known, the equivalent elastic modulus and equivalent mass density of the soft gel metamaterial can be obtained.

[0096] Next, the reflection coefficient and transmission coefficient of the soft gel metamaterial-backing plate structure are measured through steps 2 and 3.

[0097] Step 2: Reflection coefficient measurement

[0098] Soft gel metamaterial-backing plate structure reflection coefficient test device Figure 3As shown, the center frequency of the transducer is 7.5 MHz (the center frequency of the transducer is selected according to the test frequency of the material, and multiple center frequencies can be selected for wide frequency range detection). Figure 3 The distance between the hydrophone and the surface of the soft gel metamaterial is d1 (1.5 cm), the thickness of the soft gel metamaterial is d3 (2 mm), and the thickness of the backing plate is d2 (4 mm). The hydrophone receives the direct signal from the transducer and the reflected signal reflected by the soft gel metamaterial-backing plate structure. The reflection coefficient R of the soft gel metamaterial-backing plate structure in the frequency band near 7.5 MHz is obtained by Fourier transforming the reflected signal and the direct signal and dividing them.

[0099] Step 3: Transmission coefficient measurement

[0100] Transmission coefficient test device for soft gel metamaterial-backing plate structure Figure 4 As shown, first pass Figure 4 The setup in (a) uses a hydrophone to measure the direct signal from the transducer, then Figure 4 The device in (b) measures the transmission signal through the soft gel metamaterial-backing plate structure. The transmission coefficient T of the soft gel metamaterial-backing plate structure in the frequency band around 7.5MHz is obtained by Fourier transforming the transmission signal and the direct signal and dividing them.

[0101] The present invention solves the problem that the reflection signal of the soft gel metamaterial is too weak to be measured by adding a backing material behind the soft gel metamaterial. Further, by measuring the reflection signal and transmission signal of the soft gel metamaterial-backing plate structure, the equivalent acoustic parameters (equivalent mass density and equivalent elastic modulus) of the soft gel metamaterial to be measured are calculated based on the propagation theory of sound waves in any multilayer medium.

[0102] The present invention also provides a system for measuring equivalent acoustic parameters of soft ultrasonic gel materials, comprising:

[0103] A reflection coefficient measurement module, used to measure the reflection coefficient of a soft gel metamaterial-backing plate structure; the soft gel metamaterial-backing plate structure is composed of a backing plate placed behind the soft gel metamaterial;

[0104] A transmission coefficient measurement module, used to measure the transmission coefficient of the soft gel metamaterial-backing plate structure;

[0105] A soft gel metamaterial impedance determination module, used to determine the impedance of the soft gel metamaterial according to the reflection coefficient and the transmission coefficient;

[0106] a phase change determination module, configured to determine a phase change of an acoustic wave in the soft gel metamaterial based on the impedance of the soft gel metamaterial;

[0107] A sound velocity calculation module, used for calculating the sound velocity in the soft gel metamaterial according to the phase change of the sound wave in the soft gel metamaterial;

[0108] An equivalent acoustic parameter calculation module is used to calculate the equivalent acoustic parameters of the soft ultrasound gel material according to the impedance of the soft gel metamaterial and the sound velocity in the soft gel metamaterial; the equivalent acoustic parameters include an equivalent elastic modulus and an equivalent mass density.

[0109] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0110] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for determining equivalent acoustic parameters of soft ultrasonic gel materials, characterized in that: include: Measuring the reflection coefficient of a soft gel metamaterial-backing plate structure; the soft gel metamaterial-backing plate structure is composed of a backing plate placed behind the soft gel metamaterial; Measuring the transmission coefficient of the soft gel metamaterial-backing plate structure; Determining the impedance of the soft gel metamaterial according to the reflection coefficient and the transmission coefficient; determining a phase change of an acoustic wave in the soft gel metamaterial based on the impedance of the soft gel metamaterial; Calculating the speed of sound in the soft gel metamaterial according to the phase change of the sound wave in the soft gel metamaterial; Calculating equivalent acoustic parameters of the soft ultrasound gel material according to the impedance of the soft gel metamaterial and the sound velocity in the soft gel metamaterial; the equivalent acoustic parameters include an equivalent elastic modulus and an equivalent mass density; Phase transition of sound waves in the soft gel metamaterial The calculation formula is as follows: Wherein, f is the test frequency of the transducer, d3 is the thickness of the soft gel metamaterial, θ3 is the incident angle of the sound wave from the soft gel metamaterial to the backing plate, and c3 is the speed of sound in the soft gel metamaterial.

2. The method for determining equivalent acoustic parameters of soft ultrasound gel material according to claim 1, characterized in that: The method of measuring the reflection coefficient of the soft gel metamaterial-backing plate structure specifically includes: Measuring the direct signal from the transducer and the reflected signal reflected by the soft gel metamaterial-backing plate structure by a hydrophone; The reflection coefficient of the soft gel metamaterial-backing plate structure is obtained by Fourier transforming the reflected signal and the direct signal and dividing them.

3. The method for determining equivalent acoustic parameters of soft ultrasonic gel material according to claim 1, characterized in that: The measuring of the transmission coefficient of the soft gel metamaterial-backing plate structure specifically includes: Measuring the direct signal from the transducer and the transmitted signal through the soft gel metamaterial-backing plate structure by a hydrophone; The transmission signal and the direct signal are Fourier transformed and then divided to obtain the transmission coefficient of the soft gel metamaterial-backing plate structure.

4. The method for determining equivalent acoustic parameters of soft ultrasonic gel material according to claim 1, characterized in that: The calculation formula of the equivalent acoustic parameters of the soft ultrasound gel material is as follows: Among them, ρ eff is the equivalent mass density, K eff is the equivalent elastic modulus, Z3 is the impedance of the soft gel metamaterial, c3 is the sound velocity in the soft gel metamaterial, ρ3=ρ eff , ρ3 is the mass density of the soft gel metamaterial.

5. A system for measuring equivalent acoustic parameters of soft ultrasonic gel materials, characterized in that: include: A reflection coefficient measurement module, used to measure the reflection coefficient of a soft gel metamaterial-backing plate structure; the soft gel metamaterial-backing plate structure is composed of a backing plate placed behind the soft gel metamaterial; A transmission coefficient measurement module, used to measure the transmission coefficient of the soft gel metamaterial-backing plate structure; A soft gel metamaterial impedance determination module, used to determine the impedance of the soft gel metamaterial according to the reflection coefficient and the transmission coefficient; a phase change determination module, configured to determine a phase change of an acoustic wave in the soft gel metamaterial based on the impedance of the soft gel metamaterial; A sound velocity calculation module, used for calculating the sound velocity in the soft gel metamaterial according to the phase change of the sound wave in the soft gel metamaterial; An equivalent acoustic parameter calculation module, used to calculate the equivalent acoustic parameters of the soft ultrasound gel material according to the impedance of the soft gel metamaterial and the sound velocity in the soft gel metamaterial; the equivalent acoustic parameters include an equivalent elastic modulus and an equivalent mass density; Phase transition of sound waves in the soft gel metamaterial The calculation formula is as follows: Wherein, f is the test frequency of the transducer, d3 is the thickness of the soft gel metamaterial, θ3 is the incident angle of the sound wave from the soft gel metamaterial to the backing plate, and c3 is the speed of sound in the soft gel metamaterial.

6. The soft ultrasound gel material equivalent acoustic parameter measurement system according to claim 5, characterized in that: The calculation formula of the equivalent acoustic parameters of the soft ultrasound gel material is as follows: Among them, ρ eff is the equivalent mass density, K eff is the equivalent elastic modulus, Z3 is the impedance of the soft gel metamaterial, c3 is the speed of sound in the soft gel metamaterial, v3 = ρ eff , ρ3 is the mass density of the soft gel metamaterial.

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