CN101917655A - Resonant cavity microphone for sound detection in deep water - Google Patents

Abstract

The invention discloses a resonant cavity microphone for sound wave detection in deep water. The length of the air cavity in the pressure-resistant medium acoustic resonant cavity is half of the working wavelength λ of the sound wave. The microphone is installed at one end of the pressure-resistant medium acoustic wave resonant cavity, and the receiving surface of the microphone is in the air cavity. The invention can still detect the sound wave signal even in the deep water high pressure condition, and through this simple structure, it can not only maintain the high sensitivity of the traditional microphone under normal pressure measurement, but also overcome the defect that the traditional microphone cannot be used to detect the sound wave in water. The device is simple in design, small in size, low in cost and convenient to use. It can be widely used in underwater microphones for sound wave detection systems under high pressure such as deep water pipelines, oil wells, and deep seas.

Description

Resonant cavity microphone for sound detection in deep water

technical field

The invention relates to an underwater microphone, in particular to a resonant cavity microphone for sound wave detection in deep water.

Background technique

With the development of human society, wireless communication technology plays an increasingly important role in our life. The traditional electromagnetic wave wireless communication is very familiar to everyone. For example, mobile phones used in daily life and radio stations widely used in the military all transmit information through electromagnetic waves. However, in some cases, wireless communication of electromagnetic waves is not necessarily the best communication method, such as wireless communication in deep water.

Underwater communication is very difficult due to the attenuation effect of seawater on electromagnetic waves. So, can you use sound waves to transmit information? For several years, scientists from various countries have been committed to the research of submarine acoustic communication, that is, to transmit a large amount of data containing voice, text and image on the seabed in the form of sound waves. At present, the use of sound in the military is mainly concentrated in the use of sonar detection, reconnaissance and simple communication, such as identifying the position of the enemy submarine in the water based on the sound, using active sonar to search for mines, and using bathymetric sonar to determine the depth of the seabed , According to the signals sent and received by the sonar to identify the enemy and the enemy. In commercial production, there are many places that need to use sound waves. For example, deep-water communications such as mines and oil wells, how to transmit signals to the bottom of mines or oil wells to control the operation of a certain system.

Although breakthroughs have been made in acoustic wave communication technology, there are still many problems to be overcome. First, the sound waves also taper off as they travel, making the signal weaker. At the same time, since water is an excellent transmission medium for sound, all kinds of sound waves can be transmitted for hundreds of thousands of kilometers, making it difficult for people to distinguish the sound waves carrying data from the usual background noise. At present, there is no perfect acoustic wave detection instrument in underwater communication, which can work normally, stably, and with high sensitivity under ultra-high pressure conditions at a depth of thousands of meters. Although traditional hydrophones can work underwater to detect underwater sound waves and have high sensitivity, traditional hydrophones mostly work in shallow water areas within 500 meters. Under high-pressure conditions in deep water, even after passing through With a special design, its sensitivity will also deteriorate to a greater extent, and its pressure-bearing structure will also be difficult to work stably for a long time. Therefore, there is an urgent need for a new type of acoustic wave detector so that it can work under deep water and has a high detection sensitivity.

Contents of the invention

The object of the present invention is to provide a resonant cavity microphone for deep water sound wave detection, which utilizes the resonance effect of sound waves in multi-layer media, and utilizes the sound wave resonance effect to realize the energy accumulation of sound waves, so that the sound waves in deep water are coupled to the resonant cavity , and realize the accumulation of energy so that the traditional microphone can detect the sound wave coupled from the water in the resonant cavity filled with air close to the atmospheric pressure of the ground.

The technical solution adopted by the present invention to solve its technical problems is:

The length of the air cavity in the pressure-resistant medium acoustic wave resonant cavity of the present invention is half of the sound wave working wavelength λ, the microphone is installed at one end of the pressure-resistant medium acoustic wave resonant cavity, and the receiving surface of the microphone is in the air cavity.

The air cavity in the pressure-resistant medium acoustic wave resonator cavity is a cylinder or a cuboid air cavity with both ends closed.

The receiving surface of the microphone is coplanar with an inner end surface of the air cavity in the pressure-resistant medium sound wave resonant cavity.

The beneficial effect that the present invention has compared with background technology is:

The invention can still realize the detection of the sound wave signal even in the deep water high pressure condition, and overcomes the shortcoming that the traditional underwater sound detection equipment cannot work in the deep water high pressure. Moreover, through this simple structure, the high sensitivity of the traditional microphone can be maintained, and the defect that the traditional microphone cannot detect sound waves in water can be overcome, thereby providing a highly stable sound wave detection device. The device is simple in design, small in size, low in cost and convenient to use.

The invention can be widely used in underwater microphones of sound wave detection systems under high pressure such as deep water pipelines, oil wells and deep seas.

Description of drawings

Figure 1 is a schematic diagram of the reflection and transmission of sound waves in a multi-layer medium.

Figure 2 is a schematic diagram of the structure of a resonant cavity microphone.

In the figure: 1. pressure-resistant medium sound wave resonance cavity, 2. air cavity, 3. microphone, 4. deep-water pipeline, 5. water in the deep-water pipeline.

Detailed ways

The present invention will be further described below in conjunction with drawings and embodiments.

Sound waves will be reflected and transmitted in multi-layer media, especially when sound waves are vertically incident on multi-layer planes, we can use the wave equation and Euler equation to write the sound pressure p(x) and vibration velocity in each layer of media v(x), as shown in Figure 1:

Among them, the third layer of medium is the same as the first layer of medium, that is, it has the same density and the same speed of sound. The thickness of the medium in the middle layer is l, and the sound wave is incident from the first layer on the left. p _1i (x) represents the incident wave of the first layer, p _1r (x) represents the reflected wave of the first layer, ρ ₁ and c ₁ represent the density and sound velocity of the first layer medium respectively, p _2i (x) represents the incident wave of the second layer wave, p _2r (x) represents the reflected wave in the second layer, ρ ₂ and c ₂ represent the density and sound velocity of the medium in the second layer, respectively, p _3i (x) represents the transmitted wave in the third layer, ρ ₁ and c ₁ represent the The density and sound velocity of the three-layer medium.

We can successively express their sound pressure p(x) and vibration velocity v(x) in the three-layer medium, and the sound pressure p ₁ (x) and vibration velocity u ₁ (x) in the first layer medium are expressed as:

$p_1\left(x\right)=A_1{e}^{-j{k}_{1}x}+B_1{e}^{j{k}_{1}x}$ (1)

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>$

表示第一层介质里朝x负方向传播的声波算式，k₁为第一层介质里的波矢。Wherein A ₁ represents the magnitude of the sound pressure of the first layer of incident sound waves, B ₁ is the magnitude of the sound pressure of the first layer of reflected sound waves, Indicates the sound wave formula propagating in the positive direction of x in the first layer of medium,

Represents the acoustic wave formula propagating in the negative direction of x in the first layer of medium, and k ₁ is the wave vector in the first layer of medium.

The sound pressure p ₂ (x) and vibration velocity u ₂ (x) in the second layer medium are expressed as:

$p_2\left(x\right)=A_2{e}^{-j{k}_{2}x}+B_2{e}^{j{k}_{2}x}$ (2)

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>$

表示第二层介质里朝x正方向传播的声波算式，表示第二层介质里朝x负方向传播的声波算式，k₂为第二层介质里的波矢。Wherein A ₂ represents the magnitude of the sound pressure of the second layer of incident sound waves, B ₂ is the magnitude of the sound pressure of the second layer of reflected sound waves,

Indicates the sound wave formula propagating in the positive direction of x in the second layer of medium, Represents the acoustic wave formula propagating in the negative direction of x in the second layer of medium, and k ₂ is the wave vector in the second layer of medium.

The sound pressure p ₃ (x) and vibration velocity u ₃ (x) in the medium of the third layer are:

$p_3\left(x\right)=A_3{e}^{-j{k}_3(x-l)}$ (3)

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; )</span>}$

表示第三层介质里朝x正方向传播的声波算式，k₃为第三层介质里的波矢。where _A3 represents the magnitude of the sound pressure of the incident sound wave on the third layer,

Represents the sound wave formula propagating in the positive direction of x in the third layer medium, and k ₃ is the wave vector in the third layer medium.

The sound wave propagating in the three-layer medium must satisfy the continuity of sound pressure and vibration velocity at the boundary, and it can be known that the following equation is satisfied:

p ₁ (x) | _{x = 0} = p ₂ (x) | _{x = 0} p ₂ (x) | _{x = l} = p ₃ (x) | _{x = l}

...

u ₁ (x) | _{x = 0} = u ₂ (x) | _{x = 0} u ₂ (x) | _{x = l} = u ₃ (x) | _{x = l}

Simultaneously solving the above four equations, it can be solved that when the second layer of medium satisfies k ₂ l=nπ, the amplitude of the standing wave in the second layer of medium is the largest, and at this time the sound wave is transmitted from the first layer of medium to the third layer of medium The maximum transmittance is exactly equal to 1. At the same time, the sound wave resonates on the medium in the middle layer, and the energy is greatly increased. get:

$\begin{array}{cc}{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; 2</span>}}& {\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; 2</span>}}\end{array}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

It can be found that at the time of resonance, the maximum sound pressure of the sound wave in the second layer of medium is |A ₂ |+|B ₂ |, therefore, if the first and third layers of media are set to water, and the middle layer of medium If it is set as air, when the length of the air layer satisfies the above k ₂ l=nπ, the sound waves in the air layer between the water layers will resonate, making the energy accumulation in it larger.

According to the nature of the above-mentioned acoustic resonance, in order to measure the acoustic wave in deep water, an air acoustic wave resonator was made, and the measurement of the acoustic wave signal was realized through the resonance effect. In order to illustrate the working process of the resonant cavity microphone 1 , an example of sound wave signal detection in a deep water pipeline is given. As shown in Figure 2, in the vertically placed deep water pipeline 4, a pressure-resistant medium acoustic wave resonator 1, such as a steel acoustic wave resonator, is placed, which can withstand high pressure in deep water. When the length of the air cavity 2 in the pressure-resistant medium acoustic resonator 1 is just half of the working wavelength of the acoustic wave, that is, k ₂ l = nπ is satisfied, and due to the resonance effect, the sound wave will be coupled into the acoustic resonator and accumulate in it The energy increases the sound pressure inside. On the inner end face of one end of the sound wave resonator, a traditional microphone is placed so that the receiving end face of the microphone is just in the same plane as the end face, which can eliminate the influence on the resonance effect. The microphone can receive the sound wave signal in the air. When the sound wave resonator couples the sound wave signal in the water 5 in the deep water pipeline to the air cavity 2, the traditional microphone can measure the signal, thus realizing the detection of the sound wave signal in the high pressure deep water pipeline. Detection, the principle of detecting sound waves in other deep waters is similar.

The structural block diagram of the resonant cavity microphone provided by the present invention is shown in Figure 2, the length of the air cavity 2 in the pressure-resistant medium acoustic resonant cavity 1 is one-half of the working wavelength λ of the acoustic wave, and the microphone 3 is installed in the pressure-resistant medium acoustic resonant cavity 1, the receiving surface of the microphone 3 is in the air cavity 2.

The air cavity 2 in the pressure-resistant medium acoustic wave resonator cavity 1 is a cylindrical or cuboid air cavity 2 with both ends closed.

The receiving surface of the microphone 3 is coplanar with an inner end surface of the air cavity 2 in the pressure-resistant medium sound wave vibration cavity 1 .

The thickness of the pressure-resistant medium acoustic resonator 1 can be changed appropriately, and the thinner the better under the condition that the high-pressure resistance can be guaranteed; Compression signals are converted into electrical signals for processing.

The working frequency of the present invention is undetermined, and the working wavelength of the sound wave can be determined first, and then the size of the corresponding pressure-resistant medium sound wave resonant cavity can be set. At the same time, the same pressure-resistant medium sound wave resonator can work at multiple frequencies. As long as the sound wave is an integer multiple of the fundamental frequency, it can resonate in the resonator and be received by the microphone, so its working frequency band is discrete.

The above is only a preferred example of the detection in deep water pipelines of the present invention, and does not limit the present invention in any form. Any skilled person who is familiar with this field may use the technical content disclosed above to change or modify it to be equivalent. The equivalent examples of changes, but any simple modification, equivalent change and modification made to the above examples according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still belong to the scope of the technical solution of the present invention.

Claims (3)

1. resonant cavity microphone that is used for detecting deep water sound waves, it is characterized in that: air chamber (2) length in the withstand voltage medium acoustic wave resonator (1) is 1/2nd of sound wave operation wavelength λ, microphone (3) is installed in an end of withstand voltage medium acoustic wave resonator (1), and the receiving plane of microphone (3) is in the air chamber (2).

2. a kind of resonant cavity microphone that is used for detecting deep water sound waves according to claim 1 is characterized in that: the air chamber (2) in the described withstand voltage medium acoustic wave resonator (1) is the air chamber (2) of cylinder or cuboid, closed at both ends.

3. a kind of resonant cavity microphone that is used for detecting deep water sound waves according to claim 1 is characterized in that: shake an inner face coplane of the air chamber (2) in the chamber (1) of the receiving plane of described microphone (3) and withstand voltage medium sound wave.

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