Sound pressure frequency selective enhancer, test method and acquisition system

Abstract

The present invention discloses a sound pressure frequency selective enhancer, a test method, and an acquisition system, belonging to the technical field of sound source positioning. The system comprises a conductive rod and at least three conductors, all of which are sleeved on the outside of the conductive rod. The three conductors are arranged in sequence along the length direction of the conductive rod, and the cross-sections of the three conductors increase from one end of the conductive rod to the other end, and the cross-sections of the conductors intersect with the length direction of the conductive rod. As the cross-sections of the three conductors gradually increase from one end of the conductive rod to the other end, an equivalent medium with a refractive index higher than that of air is formed between adjacent conductors in the air, reducing the propagation speed of the sound wave and compressing the sound wave of the sound pressure frequency selective enhancer. Through the continuously increasing conductors, a higher sound pressure amplitude is generated, thereby enhancing the weak signal of the mechanical equipment and improving the accuracy of mechanical fault detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of sound source localization, and in particular relates to a sound pressure frequency selective enhancer, a testing method and an acquisition system. Background Art

[0002] Low-cost condition monitoring and fault diagnosis technologies are of great practical significance for maintaining the health of mechanical equipment and preventing accidents. Among the numerous fault diagnosis methods, acoustic sensing has attracted considerable attention due to its advantages, such as rich information acquired through acoustic signal acquisition, non-contact nature, and flexible installation. However, irrelevant noise, both from the environment and from the acoustic sensors themselves, can interfere with the acoustic signal and reduce the effectiveness of acoustic sensors.

[0003] Acoustic metamaterials have garnered widespread attention in recent years due to their unique wave manipulation properties. These unique properties offer promising prospects for the development of metamaterial-based sound source localization technologies. For example, randomly coded acoustic metamaterials and directional acoustic metamaterials with anisotropic acoustic responses can overcome limitations on the number of sensors. Furthermore, resonant and high-refractive-index acoustic metamaterials can utilize resonant cavities or high-refractive-index regions to capture incident acoustic waves, enabling pre-amplification of the detected sound waves.

[0004] Existing technology, such as Chinese patent number CN202111631579.8, discloses a subwavelength acoustic metamaterial coupling structure for sound source localization. This novel structure, formed by coupling a gradient refractive index structure with a spatially curled structure, can achieve sound source localization at the subwavelength scale. However, this structure has a limited range of acoustic wave frequencies. While it can detect some weak signals, it cannot enhance the sound pressure of these weak signals, resulting in low accuracy in mechanical fault detection. Summary of the Invention

[0005] The purpose of the present invention is to provide a sound pressure frequency selective enhancer, a test method and an acquisition system, which can enhance the sound pressure of weak signals and are suitable for enhancing weak signals and fault detection of mechanical equipment.

[0006] The technical solution is as follows:

[0007] A sound pressure frequency selective enhancer comprises a conductive rod and at least three conductors, wherein the three conductors are all sleeved on the outside of the conductive rod;

[0008] The three conductors are sequentially arranged along the length direction of the conductive rod, and the cross-sections of the three conductors increase sequentially from one end to the other end of the conductive rod, and the cross-sections of the conductors intersect with the length direction of the conductive rod.

[0009] In one embodiment, the number of the conductors is multiple, and the cross-sections of the multiple conductors are all circular. In the direction of the X-axis of the coordinate system, the radius of the multiple conductors is arranged as follows: z(x)=0.0007x 2 +(8~10);

[0010] Where x is the distance between the conductor and the origin of the X-axis coordinate system; z is the value of the conductor's radius on the Z-axis of the coordinate system.

[0011] In one embodiment, the center of the conductor has a through hole for the conductive rod to pass through, there is a gap between two adjacent conductors, and the distance between the two adjacent conductors is equal.

[0012] In one embodiment, the equivalent refractive index of the sound pressure frequency selective enhancer is expressed as follows:

[0013]

[0014] ω=2πf;

[0015] Where n TSAM is the equivalent refractive index of the sound pressure frequency selective enhancer; f is the frequency of the incident sound wave; ω is the angular frequency; n air is the refractive index of air to sound; β air is the bulk modulus of air; ρ air is the mass density of air; ρ z is the overall equivalent mass density of the frequency-selective sound pressure enhancer along the Z-axis; β is the overall equivalent bulk modulus of the frequency-selective sound pressure enhancer; and z is the value of the conductor's radius on the Z-axis of the coordinate system.

[0016] In one embodiment, in the relationship between the sound pressure along the X-axis and the input sound frequency, the enhanced sound pressure of the sound pressure frequency selective enhancer is expressed as follows:

[0017]

[0018] Where, P TSAM is the enhanced sound pressure of the sound pressure frequency selective enhancer; f is the frequency of the incident sound wave; ρ air is the mass density of air, ρ z is the overall equivalent mass density of the sound pressure frequency selective enhancer along the Z-axis.

[0019] In one embodiment, when the sound source is located on one side of the conductive rod and the vertical distance between the sound source and the length direction of the conductive rod remains unchanged, the sound pressure amplitude at any position within the gap on the conductive rod is equal and greater than the sound pressure amplitude outside the gap.

[0020] In one embodiment, the plurality of conductors are in a trumpet-shaped structure; the trumpet-shaped structure has an arc-shaped outer edge, and an inner arc surface of the arc-shaped outer edge faces the conductive rod.

[0021] In one embodiment, the number of the conductors is 20 to 30; the length of the conductive rod is 300 to 400 mm; the thickness of each conductor is 2.5 to 3.5 mm, and the gap between two adjacent conductors is 10 to 15 mm.

[0022] In one embodiment, at least a portion of the conductor is made of a material containing aluminum metal.

[0023] The present invention also provides a testing method, in which a sound pressure frequency selective enhancer is applied, comprising the following steps:

[0024] Step 1: Install an acoustic sensor in the gap between two adjacent conductors, wherein the acoustic sensor is electrically connected to a data receiver;

[0025] Step 2: Setting a test piece at the front end of the sound pressure frequency selective enhancer, with a detection point on the test piece;

[0026] Step 3: Start the test piece, the test piece generates sound waves, and the data receiver obtains sound wave data.

[0027] The present invention also proposes an acquisition system, comprising an acoustic sensor, a data receiver, and the sound pressure frequency selective enhancer as described above, wherein the data receiver is electrically connected to the acoustic sensor, and the acoustic sensor is installed on the sound pressure frequency selective enhancer and located in the gap.

[0028] The technical solution provided by the present invention has the following advantages and effects:

[0029] 1. Three conductors are sleeved on the outside of the conductive rod; the three conductors are arranged in sequence along the length direction of the conductive rod, and the cross-sections of the three conductors gradually increase from one end to the other end of the conductive rod, and the cross-sections of the conductors intersect with the length direction of the conductive rod; as the cross-sections of the three conductors gradually increase from one end to the other end of the conductive rod, an equivalent medium with a refractive index higher than that of air is formed between adjacent conductors in the air, which reduces the propagation speed of the sound wave and compresses the sound wave of the sound pressure frequency selective enhancer. A higher sound pressure amplitude is generated through the continuously increasing conductors, thereby enhancing the weak signal of the mechanical equipment and improving the accuracy of mechanical fault detection.

[0030] 2. The radius of multiple conductors is calculated by the formula z(x)=0.0007x 2The conductors are arranged in an orderly fashion, with the cross-sections of the multiple conductors gradually increasing along the conductive rods. This increases the frequency selection range of acoustic waves and enhances sound pressure, making it suitable for enhancing weak signals and fault detection in mechanical equipment. This frequency-selective sound pressure enhancer has a simple structure and low manufacturing cost, and offers fast optimization and flexible sensing performance. During equipment operation, it amplifies a specific frequency range of acoustic signals, thereby improving the signal-to-noise ratio. This enriches the monitoring methods for mechanical fault diagnosis and can be used for fault detection in most rotating machinery, demonstrating its strong adaptability.

[0031] 3. By calculating the equivalent refractive index of the sound pressure frequency selective enhancer, the relationship between the equivalent refractive index and the sound pressure enhancement is obtained. Based on the relationship between the overall equivalent bulk modulus of the conductor and the sound pressure enhancement, it is helpful for experimenters to select a medium that is more suitable for sound propagation.

[0032] 4. After calculating the equivalent refractive index formula and referring to the bulk modulus and density of each metal, aluminum metal is selected as the most suitable medium for sound propagation, which further generates a higher sound pressure amplitude and enhances the weak signals of mechanical equipment.

[0033] 5. Through the testing method, a detection point with defects is set on the test piece. After the test piece generates sound waves, all frequency components of the sound waves are transmitted to the data receiver through the sound pressure frequency selective enhancer. The signal-to-noise ratio of the four harmonics of the test piece's rotation is observed. The seven signals collected in the gap are significantly 25% higher than the signals collected outside the structure. It can be seen that this sound pressure frequency selective enhancer significantly improves the efficiency of fault detection, thereby verifying the analysis result that the sound pressure frequency selective enhancer can be used to increase sound pressure.

[0034] 6. Applying the sound pressure frequency selective enhancer to the acquisition system can generate a higher sound pressure amplitude, thereby enhancing the weak signals collected from mechanical equipment and improving the accuracy of mechanical fault detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 1 is a structural diagram of a sound pressure frequency selective enhancer in one embodiment of the present invention.

[0036] Figure 2 1 is a schematic diagram of an equivalent medium principle of a sound pressure frequency selective enhancer in one embodiment of the present invention.

[0037] Figure 3 This is a mathematical model calculation simulation of a sound pressure frequency selective enhancer in one embodiment of the present invention. Figure 1 .

[0038] Figure 4 This is a mathematical model calculation simulation of a sound pressure frequency selective enhancer in one embodiment of the present invention. Figure 2 .

[0039] Figure 5 The finite element analysis of the sound pressure frequency selective enhancer in one embodiment of the present invention is as follows Figure 1 .

[0040] Figure 6 The finite element analysis of the sound pressure frequency selective enhancer in one embodiment of the present invention is as follows Figure 2 .

[0041] Figure 7 The frequency response characteristic curve of the sound pressure frequency selective enhancer in one embodiment of the present invention is Figure 1 .

[0042] Figure 8 The frequency response characteristic curve of the sound pressure frequency selective enhancer in one embodiment of the present invention is Figure 2 .

[0043] Figure 9 This is a diagram showing the refraction effect of sound waves propagating through different media in one embodiment of the present invention.

[0044] Figure 10 Schematic diagram of the dimensions of a conductor in one embodiment of the present invention.

[0045] Figure 11 Schematic diagram of sound wave transmission in one embodiment of the present invention.

[0046] Figure 12 Schematic diagram of the coupling between acoustic waves and space boundaries in one embodiment of the present invention.

[0047] Figure 13 1 is a curve fitting diagram of a sound pressure frequency selective enhancer in one embodiment of the present invention.

[0048] Figure 14 Schematic diagram of a coordinate system in one embodiment of the present invention.

[0049] Figure 15 1 is a schematic diagram of a test experiment of a sound pressure frequency selective enhancer in one embodiment of the present invention.

[0050] Figure 16 This is the effectiveness data effect after the experiment in one embodiment of the present invention Figure 1 .

[0051] Figure 17 This is the effectiveness data effect after the experiment in one embodiment of the present invention Figure 2 .

[0052] Description of reference numerals:

[0053] 100. Sound pressure frequency selective enhancer; 1. Conductor; 2. Conducting rod; 3. Gap; 4. Arc outer edge; T is the thickness of the conductor; z is the value of the conductor's radius on the Z axis of the coordinate system; G is the width of the gap. DETAILED DESCRIPTION

[0054] To facilitate understanding of the present invention, specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings.

[0055] Unless otherwise specified or defined, the "first, second..." used in this article is only used to distinguish names and does not represent a specific quantity or order.

[0056] Unless stated otherwise or defined otherwise, the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0057] It should be noted that, in this document, “fixed to” or “connected to” may mean directly fixing or connecting to an element, or indirectly fixing or connecting to an element.

[0058] like Figures 1 to 6 As shown, a sound pressure frequency selective enhancer 100 includes a conductive rod 2 and at least three conductors 1, each of which is sleeved on the outside of the conductive rod 2. The three conductors 1 are arranged in sequence along the length of the conductive rod 2, and the cross-sections of the three conductors 1 increase from one end of the conductive rod 2 to the other. The cross-sections of the conductors 1 intersect with the length of the conductive rod 2. As the cross-sections of the three conductors 1 gradually increase from one end of the conductive rod 2 to the other, an equivalent medium with a higher refractive index than air is formed between adjacent conductors 1 in the air, reducing the propagation speed of sound waves and compressing the sound waves of the sound pressure frequency selective enhancer 100. Through the continuously increasing conductors 1, a higher sound pressure amplitude is generated, thereby enhancing the weak signals of mechanical equipment and improving the accuracy of mechanical fault detection.

[0059] In addition, there are multiple conductors 1, and the cross-sections of the multiple conductors 1 are all circular. In the direction of the X-axis of the coordinate system, the radius arrangement formula of the multiple conductors 1 is: z(x)=0.0007x 2 +(8~10);

[0060] Where x is the distance between the conductor and the origin of the X-axis coordinate system; z is the value of the radius of conductor 1 on the Z-axis of the coordinate system.

[0061] In this embodiment, the conductor 1 is a circular aluminum plate. The full symmetry of the circular aluminum plate is conducive to identifying the location of the sound source; the combination of the circular aluminum plate and air forms an effective medium with a refractive index much higher than that of air as a sound pressure frequency selective enhancer 100, which is used to compress the propagating sound waves in the structure, thereby generating a higher sound pressure amplitude and ultimately amplifying the sound pressure signal.

[0062] like Figure 2As shown, the key to achieving signal amplification lies in the ability of the acoustic metamaterial device to combine with air to form an effective medium with a refractive index much higher than that of air. This method enhances the sound pressure amplitude of the sound waves passing through the frequency-selective sound pressure enhancer 100, providing theoretical support for the design of the frequency-selective sound pressure enhancer 100.

[0063] like Figure 3 and Figure 4 As shown, the simulation results show that the effective refractive index and frequency characteristic model of the metamaterial are Figure 3 In the figure, under different single-frequency sound excitations, five single-frequency sounds are taken as input excitations, and significant amplification occurs along the X-axis of the coordinate system, which is related to the specific position of the designed metamaterial. Figure 4 In the figure, five separate positions are taken along the X-axis for observation, and the model shows that different fixed positions correspond to different acoustic signal frequency ranges. Overall, the analytical model shows that the smaller the radius of the aluminum plates on the left and right sides of gap 3, the lower the frequency of the amplified sound. The improvement of the selection range of sound wave frequency and the enhancement of sound pressure are achieved, which is suitable for the enhancement of weak signals and fault detection of mechanical equipment. This sound pressure frequency selective enhancer 100 has a simple structure and low production cost; it has fast optimization and flexible sensing performance; when the equipment is running, it amplifies the specific range of frequencies of the acoustic signal, thereby improving the signal-to-noise ratio of the sound signal, which enriches the monitoring means of mechanical fault diagnosis and can be used for fault detection of most rotating machinery, with strong adaptability.

[0064] like Figure 5 and Figure 6 To more accurately investigate the performance of the frequency-selective sound pressure enhancer 100, a finite element analysis was performed. Under different single-frequency excitations, the sound pressure within each gap 3 between two adjacent conductors was enhanced. Along the X-axis, each gap 3 has a detection point for sound pressure amplification. Furthermore, for gaps 3 between adjacent conductors 1 with larger diameters, the frequency of the amplified sound decreases, due to the structure's higher effective refractive index.

[0065] like Figure 7 and Figure 8 As shown in FIG. 1 , under different single-frequency excitations, the sound pressure inside each gap of the sound pressure frequency selective enhancer 100 is enhanced, wherein, Figure 7 is the enhanced time domain sound signal collected in each gap, Figure 8The corresponding frequency response curve is shown in FIG. It shows that the structure can selectively divide the broadband sound signal by frequency in the gap position of different aluminum plates, and produce a higher local sound pressure amplification of the sound amplitude. The principle is: when the sound wave is incident from a low refractive index propagation medium to a high refractive index propagation medium, according to Snell's law, the speed of the sound wave will decrease. The equivalent refractive index of this sound pressure frequency selective enhancer 100 is higher than that of air, and the effective refractive index increases with the increase of the radius of the aluminum plate (increases along the X-axis direction), so the horn shape of the designed sound pressure frequency selective enhancer 100 forms a structure with a refractive index gradient change. The speed of the sound wave decreases in the high refractive index medium, and is compressed between the two circular aluminum plates, thereby increasing the amplitude of the sound pressure, but the total energy remains unchanged.

[0066] like Figure 7 and Figure 8 As shown, when the amplitude of the input sound pressure is 1Pa plane wave, the large diameter aluminum circular plate takes the waveform of the frequency response range of the sound pressure frequency selective enhancer 100 from 1Hz to 3000Hz in 5 consecutive adjacent gaps 3. Figure 7 and Figure 8 It can be seen that the device can amplify the sound pressure by up to 5 times.

[0067] like Figure 1 As shown, in order to collect the sound signal enhanced by the sound pressure frequency selective enhancer 100, an acoustic sensor (not shown in the figure) is inserted in the gap 3 between two adjacent aluminum plates. Multiple acoustic sensors are controlled by the same control circuit board to achieve synchronous sound signal collection. The control circuit board is electrically connected to the data receiver to form a multi-channel selective sound enhancement collection system. When facing rotating machinery with different working conditions, different models and sizes, this sound pressure frequency selective enhancer 100 can selectively adopt the enhanced sound pressure of each channel, so that the sound pressure frequency selective enhancer 100 can adapt to the status detection and fault diagnosis of various types of mechanical equipment.

[0068] The formula for arranging the radius sizes of the multiple conductors 1 is derived in the following manner: The main function of this sound pressure frequency selective enhancer 100 is the frequency selective enhancement of sound signals; this effect is based on the effect produced by the propagation of sound in a medium with a gradient high refractive index. However, it is difficult to find a medium (i.e., a natural material) with a higher refractive index than air in nature. Therefore, this sound pressure frequency selective enhancer 100 adopts the idea of ​​metamaterials, by artificially creating a medium (material or structure) with a higher refractive index than air, in order to achieve the effect of enhancing sound in a specific frequency band.

[0069] When designing this structure, it was important to consider the refractive index during sound propagation. The refractive index is a physical quantity that describes the changes in speed and direction of waves as they propagate through different media. When a wave propagates from one medium (such as air) to another (such as glass or water), the propagation speed of light changes and the direction of the light is deflected due to the different properties of the medium.

[0070] like Figure 9 As shown in Figure 2, the refraction of waves propagating through different media is determined by Snell's law, also known as the law of refraction. This law describes the refraction of waves propagating between two media. It can be expressed mathematically as follows:

[0071]

[0072] Among them, n i is the refractive index of the medium; θ1 is the incident angle; θ2 is the refraction angle; c i is the speed of the wave in the medium. Therefore, if we only consider the sound wave incident vertically from the air into medium 2 (incident angle 90°), and regard medium 2 as the designed acoustic metamaterial, that is:

[0073] n1→n air

[0074] n2→n TSAM

[0075] c1→c air

[0076] c2→c TSAM

[0077] Substituting into formula (1), we get:

[0078]

[0079] Among them, n air is the refractive index of air; n TSAM is the equivalent refractive index of the sound pressure frequency selective enhancer 100; c air is the speed of sound in air; C TSAM is the speed at which sound propagates in the sound pressure frequency selective enhancer 100 .

[0080] From formula (2), we can see that c air =343m / s,n air =1, is a constant, when c TSAM The smaller the speed of sound in the structure, the lower the equivalent refractive index of the structure. In other words, another function of the sound pressure frequency selective enhancer 100 is to reduce the speed of sound waves in the structure, thereby increasing the refractive index.

[0081] So how do we reduce the speed of sound? According to acoustic wave theory, the speed of sound is determined by the constitutive parameters of the medium in which it propagates, namely the bulk modulus β and the equivalent density ρ (for details, please refer to acoustic wave theory). The specific formula is as follows:

[0082]

[0083] Thus, these two constitutive parameters can be artificially designed to achieve physical properties that the designed medium does not possess compared to natural media. The special physical property achieved by the sound pressure frequency selective enhancer 100 is the frequency selective enhancement of sound. This sound pressure frequency selective enhancer 100 uses aluminum as one of its materials, and through the configuration of the ratio with air, the above two constitutive parameters are designed as follows:

[0084]

[0085] Among them, β Al is the bulk modulus of aluminum (70 GPa); β air is the bulk modulus of air (1.4×10 5 Pa); ρ Al The density of aluminum (2700kg / m 3 );ρ air is the density of air (1.2 kg / m 3 );ρ z is the equivalent density of conductor 1 in the Z-axis direction of the coordinate system; ρ x is the equivalent density of conductor 1 in the X-axis direction of the coordinate system; β is the equivalent bulk modulus; F r is the volume ratio of aluminum to air, such as Figure 10 As shown, take one of the units and observe, Where T is the thickness of the conductor and G is the width of the gap.

[0086] Assume that the sound wave is incident on the ZX plane of the coordinate system from left to right, such as Figure 11 As shown, the sound wave propagates along the X-axis of the coordinate system and oscillates along the Z-axis. The expression of its sound pressure with respect to time and space can be:

[0087]

[0088] According to the linear Euler relationship, and Newton's second law like Figure 11 As shown, combined with formula (4), we can get:

[0089]

[0090]

[0091] Integrating both sides of formula (6) and formula (7), we can obtain:

[0092]

[0093]

[0094] Formula (8) is the vibration velocity of air molecules along the Z-axis of the coordinate system; Formula (9) is the vibration velocity of air molecules along the X-axis of the coordinate system. Where P is the sound pressure; P0·cos(k z z) is the amplitude expression of vibration along the Z-axis direction of the coordinate system; k z is the wave number propagating along the Z axis of the coordinate system; ω is the angular frequency; k x is the wave number propagating along the X-axis of the coordinate system; u z is the vibration velocity of air particles vibrating along the Z axis of the coordinate system; u x is the vibration speed of air particles vibrating along the X-axis of the coordinate system.

[0095] In addition, if Figure 14 As shown, for the wave number k in any direction in any sound field, the following relationship exists:

[0096]

[0097]

[0098]

[0099] in, is the unit vector of the wave vector k; is the unit vector of the X axis; is the unit vector of the Y axis; is the unit vector of the Z axis.

[0100] for Figure 11 The coordinate system of the X-axis-Z-axis plane (not considering the Y-axis direction) can be obtained according to the above expression formula (3), formula (10), formula (11), and formula (12):

[0101]

[0102]

[0103]

[0104]

[0105]

[0106]

[0107] The above expression (13) is the frequency dispersion relationship of the sound wave during the propagation of the sound pressure frequency selective enhancer 100. In addition, the mathematical model of the sound pressure frequency selective enhancer 100 makes the following assumptions: relative to the density and modulus of air, the density and modulus of the selected aluminum material are considered to be infinite, that is, ρ Al =∞、β Al =∞, combined with the constitutive parameter formula (4), it can be simplified to:

[0108]

[0109] Next, it is necessary to analyze the structure of the sound pressure frequency selective enhancer 100 and the boundary conditions of the air, such as Figure 12 As shown, it is the boundary between region 1 and region 2. In this boundary, the evanescent wave propagates along the X-axis of the coordinate system in the gap 3 between the two adjacent guides, and attenuates along the Z-axis of the coordinate system.

[0110] For the sound field on the boundary between area 2 and area 1, the expression of the sound field in area 2 can be as follows:

[0111]

[0112] Similar to the derivation process of formula (5) to formula (9), the vibration velocity of air particles in area 2 can be derived as:

[0113]

[0114]

[0115] Where P2 is the expression of the sound pressure in area 2; P air2 is the sound pressure amplitude in area 2; P air3 is the sound pressure amplitude in area 3; k z_air is the wave vector in the Z-axis direction of the coordinate system of region 2; u 2x is the equivalent vibration velocity of air particles in the X-axis direction of the coordinate system of region 2; u 2z is the equivalent vibration velocity of air particles in the Z-axis direction of the coordinate system of region 2; u 3z is the equivalent vibration velocity of air particles in the Z-axis direction of the coordinate system of region 3; u 3x is the equivalent vibration velocity of air particles in the X-axis direction of the coordinate system of region 3.

[0116] Due to the symmetry along the X-axis, for region 3, the following equation can be derived by analogy:

[0117]

[0118]

[0119]

[0120] P3(x,z,t)=P2(x,z,t), Formula (21);

[0121] P air3 =P air2 , formula (22);

[0122] Next, based on the relationship between the equal physical quantities of the boundaries, we can conclude that:

[0123] P2(x,z,t)=P1(x,z,t), Formula (23);

[0124] Right now: Formula (24).

[0125] Likewise, Figure 12 As shown, at the boundary between area 1 and area 2, the vibration velocity equation of the air medium is:

[0126] u z (x,z,t)=u 2z (x,z,t);

[0127] Right now:

[0128]

[0129] Dividing the above expression (25) by (26) yields:

[0130]

[0131] Right now:

[0132] In regions 2 and 3, the wave numbers in each direction have the following relationship:

[0133] k z_air 2 =k x 2 -k air 2 , formula (29);

[0134]

[0135] At the same time, the wave number along the X-axis direction and the equivalent refractive index of the sound pressure frequency selective enhancer 100 satisfy the following relationship:

[0136] k x =k air ·n TSAM , formula (31).

[0137] Therefore, substitute formula (29), formula (30), formula (31) and formula (13) into formula (28):

[0138]

[0139]

[0140]

[0141]

[0142]

[0143]

[0144] Inverse n TSAM have:

[0145]

[0146] Right now:

[0147] Formula (32) is an expression for the equivalent refractive index, which is a function of the frequency of the incident sound wave and the radius of the aluminum plate. The above formula "1" can be regarded as the refractive index n of air. air , x is the distance between conductor 1 and the origin of the coordinate system X axis, z is the value of the radius of conductor 1 on the coordinate system Z axis, reverse z(x:

[0148]

[0149] Where f is the frequency of the sound wave, the formula (33) shows that n TSAM It is a function of frequency and the radius z(x) of conductor 1. Assuming that the radius z(x) of conductor 1 is a smooth function along the X-axis of the coordinate system, gradually increasing z(x) can adjust the equivalent refractive index of the overall structure of the sound pressure frequency selective enhancer 100, so that the refractive index is distributed in a gradient along the propagation direction. However, in actual practice, it is difficult to produce a device with a continuous and smooth equivalent refractive index function. According to the frequency requirements of actual rotating machinery fault diagnosis, the geometric dimensions of this sound pressure frequency selective enhancer 100 are based on Figure 10 , combined with formula (4), select T = 3mm, G = 13mm, β air =1.4×10 5 Pa, ρ air =1.2kg / m 3 , ρ Al =2700kg / m 3 , β Al =70GPa, n TSAM∈(1, 6), f = 1361Hz, substitute into formula (33) for numerical calculation and curve fitting, the fitting result is as follows Figure 13 As shown, the analytical expression of this curve fitting is: z(x=0.0007x 2 +9(0≤x≤350mm).

[0150] like Figure 1 As shown, the center of conductor 1 has a through-hole for conducting rod 2 to pass through. A gap 3 is formed between two adjacent conductors 1, and the distance between the two adjacent conductors 1 is equal. After this conductor 1 passes through the center of the conducting rod 2, due to the symmetry of the circular conductor 1 in multiple directions, the sound pressure enhancement collected by the gap 3 between two adjacent conductors 1 is the same for any sound source at any position along the entire circumference after being amplified by the conductor 1.

[0151] According to the structural derivation formula of the above-mentioned sound pressure frequency selective enhancer 100, the equivalent refractive index of the sound pressure frequency selective enhancer 100 is expressed as follows:

[0152]

[0153] ω=2πf;

[0154] Where n TSAM is the equivalent refractive index of the sound pressure frequency selective enhancer 100; f is the frequency of the incident sound wave; ω is the angular frequency; n air is the refractive index of air to sound; β air is the bulk modulus of air; ρ air is the mass density of air; ρ z is the overall equivalent mass density of the sound pressure frequency selective enhancer 100 along the Z-axis; β is the overall equivalent bulk modulus of the sound pressure frequency selective enhancer 100; and z is the value of the radius of the conductor 1 on the Z-axis of the coordinate system.

[0155] By calculating the equivalent refractive index of the sound pressure frequency selective enhancer 100, the relationship between the equivalent refractive index and the sound pressure enhancement is obtained. Based on the relationship between the overall equivalent bulk modulus of the conductor 1 and the sound pressure enhancement, it is helpful for experimenters to select a medium that is more suitable for sound propagation.

[0156] In addition, regarding the relationship between the sound pressure along the X-axis and the input sound frequency, in this embodiment, the length direction of the conductive rod 2 is the X-axis direction of the coordinate system, and the expression formula for the enhanced sound pressure of the sound pressure frequency selective enhancer 100 is:

[0157]

[0158] Where, P TSAM is the enhanced sound pressure of the sound pressure frequency selective enhancer 100; f is the frequency of the incident sound wave; ρ airis the mass density of air, ρ z is the overall equivalent mass density of the sound pressure frequency selective enhancer 100 along the Z-axis.

[0159] In addition, when the sound source is located on one side of the conductive rod 2 and the vertical distance between the sound source and the length direction of the conductive rod 2 remains unchanged, the sound pressure amplitude at any position within the gap 3 on the conductive rod 2 is equal and greater than the sound pressure amplitude outside the gap 3.

[0160] Furthermore, the plurality of conductors 1 are in a trumpet-shaped structure having an arc-shaped outer edge 4, the inner arc surface of which faces the conductive rod 2. The sound pressure frequency selective enhancer 100 can enhance the sound pressure of the sound signal according to the frequency in different gaps 3 thereof.

[0161] Furthermore, there are 24 conductors 1; the length of the conductive rods 2 is 350 mm; each conductor 1 is 3 mm thick, and the gap 3 between two adjacent conductors 1 is 12 mm. At least a portion of the conductors 1 is made of a material containing aluminum. Aluminum was selected as a more suitable medium for sound propagation based on the formula for equivalent refractive index, as well as the bulk modulus and density of various metals. This results in a higher sound pressure amplitude, enhancing weak signals from mechanical equipment.

[0162] like Figures 15 to 17 As shown, in order to verify the performance of the sound pressure frequency selective enhancer 100, an electric fan fault detection experiment based on the device was conducted. The present invention also proposes a mechanical fault testing method, in which the sound pressure frequency selective enhancer 100 is applied, comprising the following steps:

[0163] Step 1: Install an acoustic sensor in the gap 3 between two adjacent conductors 1, and electrically connect the acoustic sensor to a data receiver;

[0164] Step 2: a test piece having a detection point is set at the front end of the sound pressure frequency selective enhancer 100; the test piece is located 1 meter away from the front end of the sound pressure frequency selective enhancer 100;

[0165] Step 3: Start the test piece, which generates sound waves. The sound waves are played at a frequency of 1 Hz to 3000 Hz within 20 seconds, and the data receiver obtains the sound wave data.

[0166] To simulate the common situation of pitting corrosion on a test piece, a defect was made on one of the seven blades of an electric fan. The envelope analysis was performed with the second blade passband as the center frequency and a bandwidth of 200Hz. The envelope spectrum obtained is as follows: Figure 16 It can be observed that the frequency and harmonic components of the rotating faulty blade are retained in the sound signal obtained inside the sound pressure frequency selective enhancer 100. This function is very critical for fault detection.

[0167] like Figure 17 As shown, in terms of the quality of the acoustic signal collected in the gap of this sound pressure frequency selective enhancer 100, the signal-to-noise ratio of the four harmonics of the fan speed is observed. The seven signals collected in the gap 3 are obviously 25% higher than the signals collected outside the structure. It can be seen that this sound pressure frequency selective enhancer 100 significantly improves the efficiency of fault detection, thereby verifying the analytical result that the sound pressure frequency selective enhancer 100 can be used to increase sound pressure.

[0168] A frequency-selective sound pressure enhancer 100, based on acoustic theory, is fabricated as follows: Based on acoustic theory, the equivalent mass density and modulus of the acoustic metasurface are simulated and calculated to obtain the effective refractive index of the metamaterial, along with the device's structural parameters and effective frequency response range. The obtained structural parameters are used to create a three-dimensional solid model in 3D software, which is then fabricated into a finished product and polished.

[0169] The present invention also provides a data acquisition system comprising an acoustic sensor, a data receiver, and the aforementioned sound pressure frequency selective enhancer 100. The data receiver is electrically connected to the acoustic sensor, which is mounted on the sound pressure frequency selective enhancer 100 and located in gap 3. Application of the sound pressure frequency selective enhancer 100 to the data acquisition system enables the system to generate higher sound pressure amplitudes, thereby enhancing weak signals collected from mechanical equipment and improving the accuracy of mechanical fault detection.

[0170] The above embodiments are not exhaustive and may include many other embodiments not listed above. Any replacements and improvements made without violating the concept of the present invention are within the scope of protection of the present invention.

Claims

1. A sound pressure frequency selective enhancer, characterized in that: It comprises a conductive rod and at least three conductors, wherein the three conductors are all sleeved outside the conductive rod; The three conductors are sequentially arranged along the length direction of the conductive rod, and the cross-sections of the three conductors increase sequentially from one end to the other end of the conductive rod, and the cross-sections of the conductors intersect with the length direction of the conductive rod; The plurality of conductors are in a trumpet-shaped structure; the trumpet-shaped structure has an arc-shaped outer edge, the inner arc surface of the arc-shaped outer edge facing the conductive rod; At least a portion of the conductor is made of a material containing aluminum metal; The equivalent refractive index of the sound pressure frequency selective enhancer is expressed as follows: ； Where, is the equivalent refractive index of the sound pressure frequency selective enhancer; is the frequency of the incident sound wave; ω is the angular frequency; is the refractive index of air to sound; is the bulk modulus of air; is the mass density of air; is the overall equivalent mass density of the frequency-selective sound pressure enhancer along the Z-axis; is the overall equivalent bulk modulus of the frequency-selective sound pressure enhancer; is the value of the conductor's radius on the Z axis of the coordinate system.

2. The sound pressure frequency selective enhancer according to claim 1, wherein: There are multiple conductors, and the cross-sections of the multiple conductors are all circular. In the direction of the X-axis of the coordinate system, the radius arrangement formula of the multiple conductors is: ; Where, ; is the value of the conductor's radius on the Z axis of the coordinate system.

3. The sound pressure frequency selective enhancer according to claim 2, wherein: The center of the conductor has a through hole for the conductive rod to pass through, there is a gap between two adjacent conductors, and the distance between every two adjacent conductors is equal.

4. The sound pressure frequency selective enhancer according to claim 1, wherein: In the relationship between the sound pressure along the X-axis and the input sound frequency, the expression formula of the enhanced sound pressure of the sound pressure frequency selective enhancer is: Where, The enhanced sound pressure of the sound pressure frequency selective enhancer; is the frequency of the incident sound wave; is the mass density of air, is the overall equivalent mass density of the sound pressure frequency selective enhancer along the Z-axis.

5. The sound pressure frequency selective enhancer according to claim 4, wherein: When the sound source is located on one side of the conductive rod and the vertical distance between the sound source and the length direction of the conductive rod remains unchanged, the sound pressure amplitude at any position in the gap on the conductive rod is equal and greater than the sound pressure amplitude outside the gap.

6. The test method is characterized in that Applying the sound pressure frequency selective enhancer according to claim 1 to a testing method comprises the following steps: An acoustic sensor is installed in a gap between two adjacent conductors, wherein the acoustic sensor is electrically connected to a data receiver; A test piece is set at the front end of the sound pressure frequency selective enhancer, and a detection point is provided on the test piece; The test piece is started to generate sound waves, and the data receiver acquires sound wave data.

7. The acquisition system is characterized in that The device comprises an acoustic sensor, a data receiver and the sound pressure frequency selective enhancer according to any one of claims 1 to 5, wherein the data receiver is electrically connected to the acoustic sensor, and the acoustic sensor is mounted on the sound pressure frequency selective enhancer and located in the gap.

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