JP2009005144A - Sound collecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound collecting apparatus collecting the sonic waves while improving a detection efficiency of sonic waves. <P>SOLUTION: A sound collecting apparatus 1 comprises: a horn unit 3 including a horn body formed into a hollow tubular shape wherein an area of one of both opening end faces is wider than an area of the other end face, and a vibrating film spread over an inner wall in the vicinity of one end face of the horn body so as to close the relevant one end face; an optical fiber 5 passed through a center of the vibrating film of the horn unit 3 and supported between the relevant vibrating film and a fixed portion bonded to an inner wall in the vicinity of the other end face of the horn unit 3; optical fiber Bragg grating 7 provided between the vibrating film and the fixed portion for emitting reflection light with vibration as distortion; an optical fiber distortion measuring means 9; and a conversion device 11. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sound collection device using an FBG (optical fiber Bragg grating).

  At present, if you want to detect sound waves and record sound in a wide outdoor area such as the F1 circuit or racetrack, prepare as many microphones as there are appropriate for the place and connect them with cables. I have to do it. Also, since the audio signal output from the microphone is extremely weak, signal quality is likely to deteriorate due to propagation attenuation and is not suitable for long-distance transmission in a wide place.

  Furthermore, when many microphones are connected outdoors with cables, the outdoors are not in an electrically favorable environment compared to indoors such as studios, so it is necessary to consider the effects of external noise due to electromagnetic induction. .

Thus, conventionally, a method of detecting sound waves using an FBG (optical fiber Bragg grating) has been disclosed. For example, a method of increasing the area for receiving sound waves by diffracting many FBGs, or a thin film such as a vibrating membrane of a microphone A method of applying a force to the FBG from a thin film by directly attaching the FBG to the FBG is disclosed (for example, see Non-Patent Documents 1 and 2).
T.A. Iida, et al. , Proc. OFS 15, TuP29, 239 (2003). S. Knudsen, et al. , Proc. OFS 10, 396 (1994).

  However, the conventional method using the FBG has a problem that the detection efficiency for detecting the sound wave is low when put into practical use. Note that the greatest cause of the low detection efficiency is derived from the difficulty in achieving impedance matching between air, which is a sound wave medium, and the optical fiber.

  Therefore, an object of the present invention is to provide a sound collection device that can solve the above-described problems, improve the detection efficiency of sound waves, and pick up the sound waves.

  In order to solve the above-described problem, a sound collecting device according to claim 1 is a sound collecting device that collects sound using incident light incident on an optical fiber, and includes a horn unit, an optical fiber, and an optical fiber Bragg. It was set as the structure provided with a grating, a distortion measurement means, and a conversion means.

  According to such a configuration, in the sound collecting device, the sound (sound wave) in the air flowing in from the other end surface of the horn body is condensed by the horn unit toward one end surface narrower than the other end surface, and in the vicinity of the one end surface. Sound (sound wave) can be efficiently captured by vibrating the vibrating membrane attached to the inner wall of the. In addition, the horn unit transmits sound waves arriving from a direction perpendicular to the other end surface (the one end surface is closed and open, so that it is an open surface), and the wind instrument trumpet (so-called trumpet). The sound can be collected efficiently by the same principle that makes it easy to transmit sound in the opening direction.

  Also, in the sound collection device, the vibration of the vibration film is distorted by the optical fiber Bragg grating due to the optical fiber and the optical fiber Bragg grating, and the incident light is reflected by the distorted optical fiber Bragg grating to become reflected light. The sound wave collected by the horn unit can be transmitted as reflected light by being transmitted through the optical fiber.

  Then, the sound collection device measures the reflected light emitted with respect to the incident light as a spectrum of an arbitrary wavelength as distortion generated in the optical fiber Bragg grating by the vibration of the horn unit vibrating by the distortion measuring means. Then, the sound collecting device converts the fluctuation speed and the fluctuation wavelength width when the peak of the spectrum measured by the distortion measuring means fluctuates with time by the converting means to the frequency and sound pressure of the sound collected by the horn unit. Convert.

  The sound collection device according to claim 2 is the sound collection device according to claim 1, wherein a plurality of the horn units are provided, and the optical fiber extends from a hole provided in the other end surface or the horn body. Inserted into the other end surface of the other horn unit or the hole provided in the horn main body of the horn unit, penetrates the center of the diaphragm of the horn unit, and The diffraction gratings of the fiber Bragg grating are formed to have different intervals, and the strain measuring means measures each reflected light as a spectrum of different wavelengths.

  According to such a configuration, the sound collecting device forms the optical fiber Bragg gratings in the plurality of horn units so that the intervals of the diffraction gratings of the optical fiber Bragg gratings are different, so that the wavelength of each reflected light is different. It becomes different, and it can measure as a spectrum of a different wavelength with a distortion measurement means.

  According to the first aspect of the present invention, the sound (sound wave) captured by the horn unit becomes the vibration of the vibrating membrane, and this vibration is detected as the distortion of the optical fiber Bragg grating, thereby improving the sound wave detection efficiency. Thus, the sound wave can be collected.

  According to the invention described in claim 2, since the reflected light emitted from the optical fiber Bragg grating in the plurality of horn units can be measured as a spectrum of different wavelengths, a plurality of locations where the horn unit is disposed. You can pick up sound. For this reason, by connecting a plurality of horn units with a single optical fiber, it is possible to simplify the apparatus configuration when collecting sound at a plurality of locations as compared with the case of using a conventional microphone.

Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
(Configuration of sound collection device)
FIG. 1 is an overview of the sound collection device. As shown in FIG. 1, the sound collecting device 1 includes a plurality of horn units 3 (3 ₁ , 3 ₂ , 3 ₃ ,...), An optical fiber 5, and an optical fiber Bragg grating 7 (7 ₁ , 7 ₂ , 7 ₃ ,...), An optical fiber strain measuring device (strain measuring means) 9, and a converting device (converting means) 11.

  In the sound collecting device 1, a plurality of horn units 3 are connected by a single optical fiber 5. One end of the optical fiber 5 is connected to the optical fiber strain measuring device 7, and the other end of the optical fiber 5 is connected to an arbitrary place. Although only three horn units 3 are shown here, any number may be used.

The horn unit 3 (3 ₁ , 3 ₂ , 3 ₃ ,...) Is for efficiently collecting sound in the air (sound wave), and from the area of one end face (throat face) of both open end faces. Also, the other end surface (opening surface) is formed in a hollow cylindrical shape. In addition, the horn unit 3 (3 ₁ , 3 ₂ , 3 ₃ ,...) Includes an opening that opens in the shape of a conical bottom (a trumpet shape), and a columnar throat that has a shorter radius than the opening. You may comprise. In this embodiment, the material of the horn unit 3 is hard vinyl chloride. However, the material of the horn unit 3 is not limited to vinyl chloride, and may be formed of a material such as plastic or plywood. The horn unit 3 is provided with a vibration film and an installation portion as will be described later.

  The optical fiber 5 connects a plurality of horn units 3, passes through the center of the diaphragm of the horn unit 3 (details will be described with reference to FIG. 2), and the diaphragm and the horn unit. It is supported between a mounting portion (details will be described with reference to FIG. 2) joined to the inner wall near the other end surface.

The optical fiber Bragg grating 7 (7 ₁ , 7 ₂ , 7 ₃ ,...) Is connected to the optical fiber 5, creates a diffraction grating with a constant interval in the optical fiber, and transmits only light of a specific wavelength. It has a property of reflecting, and is used as a sensor (optical fiber sensor) that detects the vibration of the vibration film provided inside the horn unit 3.

  In the optical fiber Bragg grating 7, diffraction gratings are formed at different intervals for each of the horn units 3. For this reason, the incident light incident on the optical fiber Bragg grating 7 from the optical fiber strain measurement device 9 becomes reflected light of a different wavelength and returns to the optical fiber strain measurement device 9.

  Further, the optical fiber Bragg grating 7 can express the change in the vibration as vibration amount of the reflected light (sound pressure) and change speed (sound wave frequency) with respect to the vibration of the vibrating membrane.

Here, with reference to FIG. 2, the detailed structure of the horn unit 3 and the optical fiber Bragg grating 7 is demonstrated.
FIG. 2 is a view showing the inside of the horn unit 3.
The horn unit 3 includes a horn main body 3a, a thin vibration membrane (for example, several μm to several tens μm in thickness) 3b attached so as to close one end surface (throat surface) of the horn unit 3, and an installation portion 3c. It is equipped with. The optical fiber Bragg grating 7 is bonded to the optical fiber 5 between the center portion of the vibration film 3b and the apex of the installation portion 3c.

  The optical fiber Bragg grating 7 is stretched (fixed in a pulled state) and is in a state in which a tension bias is applied in advance. Due to this tension, the optical fiber Bragg grating 7 is perpendicular to the film surface of the vibration film 3b, and the optical fiber Bragg grating 7 itself forms a straight line.

  Further, the vibrating membrane 3b is configured so that air does not enter and exit from the inside and outside of the vibrating membrane 3b (so as to block the throat surface), and vibrates with sound waves captured by the horn unit 3. In this embodiment, the material of the vibration film 3b is synthetic rubber. However, the material of the vibration film 3b is not limited to synthetic rubber, and may be formed of a light and easy to vibrate material such as Japanese paper or a polymer film (aramid film).

One end of the mounting portion 3c is joined to the inner wall of the horn body 3a, and the other end (vertex) fixes the optical fiber Bragg grating 7. In this embodiment, the material of the mounting portion 3 c is acrylic, the shape is a long and narrow bar, and it has a fixed end for fixing the optical fiber 5. However, the material of the installation part 3c is not limited to acrylic, and may be formed of a material having high rigidity such as a metal such as steel.
Returning to FIG.

  The optical fiber strain measuring device 9 includes a light source (not shown), an interferometer (not shown), and a personal computer (not shown). In this optical fiber strain measuring device 9, incident light incident on the optical fiber 5 from the light source is reflected by the optical fiber Bragg grating 7 to become reflected light, and the wavelength (nm) of the reflected light is measured by an interferometer, Recorded on a computer.

  Since the optical fiber Bragg grating 7 provided in each horn unit 3 has a different wavelength of reflected light, it is clear which horn unit 3 has collected sound.

  The conversion device 11 uses the frequency and sound of the sound collected by the horn unit 3 to indicate the fluctuation speed and fluctuation wavelength width (in nm unit) when the peak of the spectrum measured by the optical fiber strain measurement device 9 fluctuates with time. It is converted into a pressure (an audio file containing these pieces of information). In addition, this conversion apparatus 11 can be comprised with the existing software and hardware.

  According to the sound collection device 1, the horn unit 3 can capture sound waves in the air (in the air), and the sound waves captured by the horn unit 3 become vibrations of the vibration film 3b, and this vibration is converted into an optical fiber Bragg grating. By detecting the distortion as 7, the detection efficiency of the sound wave can be improved and the sound wave can be collected.

Here, an example in which the sound collection device 1 is used in the F1 circuit will be described with reference to FIG. In this example, eight horn units 3 (3 ₁ , 3 ₂ , 3 ₃ , 3 ₄ , 3 ₅ , 3 ₆ , 3 ₇ , 3 ₈ ) are installed on the curve and straight course of the F1 circuit, and these horns The units 3 are connected by an optical fiber 5.

Then, as shown in FIG. 3, for example, the horn unit _{3 1,} 3 2, _{3 3,} the spectrum of each wavelength nm (the predetermined wavelength), and detects the sound waves.

(Operation of sound collection device)
Next, the operation of the sound collection device 1 will be described with reference to the flowchart shown in FIG. 4 (see FIGS. 1 and 2 as appropriate).
First, the sound collection device 1 catches a sound wave in the air by the horn unit 3 (the sound wave is input to the horn unit 3) (step S1).
Then, in the sound collection device 1, the vibration film 3b of the horn unit 3 vibrates, and this vibration is output as reflected light by the optical fiber Bragg grating 7 (step S2).

  Then, the sound collection device 1 detects the presence or absence of a peak at a predetermined wavelength for the reflected light returned by the optical fiber strain measurement device 9 (step S3). Then, the sound collection device 1 outputs the change in the peak as sound by the conversion device 11 (step S4).

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. For example, in the present embodiment, the case where there are a plurality of horn units 3 has been described, but one horn unit 3 may be provided. Further, although the optical fiber Bragg grating 7 is stretched vertically with respect to the vibration film 3b, it may be inclined as long as the correction means for correcting the detected sound is used separately. The fiber Bragg grating 7 may not be fixed to the center of the vibration film 3b.

It is a general-view figure of the sound collection device which concerns on embodiment of this invention. It is the figure which showed the detail of the horn unit. It is the figure which showed the case where a sound-collecting apparatus was used by F1 circuit. It is the flowchart which showed operation | movement of the sound collection device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sound collecting device 3 Horn unit 3a Horn main body 3b Vibrating membrane 3c Installation part 5 Optical fiber 7 Optical fiber Bragg grating 9 Optical fiber distortion measuring device (strain measuring means)
11 Conversion device (conversion means)

Claims (2)

A sound collecting device that collects sound using incident light incident on an optical fiber,
A horn body formed in a hollow cylindrical shape having an area of the other end face wider than an area of one end face of the both open end faces, and vibration attached to the inner wall near the one end face so as to close the one end face of the horn body A horn unit having a membrane;
An optical fiber that passes through the center of the diaphragm of the horn unit and is supported between the diaphragm and an installation portion that is joined to the inner wall of the horn unit;
An optical fiber Bragg grating that emits the reflected light as a change in the wavelength of the reflected light, which is provided in the optical fiber between the vibrating membrane and the installation part, and is caused by the pressure caused by the vibration,
Strain measurement that measures the reflected light emitted to the incident light as a spectrum of an arbitrary wavelength as distortion generated in the optical fiber Bragg grating due to vibration of the vibration film of the horn unit connected to the optical fiber Means,
Conversion means for converting the fluctuation speed and fluctuation wavelength width when the peak of the spectrum measured by this distortion measurement means fluctuates with time into the frequency and sound pressure of the sound collected by the horn unit;
A sound collecting device comprising: A plurality of the horn units are provided,
The optical fiber extends from the hole provided in the other end surface or the horn body, and is inserted into the other end surface of the other horn unit or the hole provided in the horn body of the horn unit, Penetrates the center of the diaphragm of the horn unit,
For each of the horn units, the distance between the diffraction gratings of the optical fiber Bragg grating is formed differently,
The sound collection device according to claim 1, wherein the distortion measuring unit measures each reflected light as a spectrum of different wavelengths.

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