Sound measuring instrument

Abstract

A sound meter (100) comprises: a light source (111) that emits laser light; a frame unit (120) that surrounds a predetermined space, through which sound passes, so as to intersect a travelling direction of the sound, the frame unit (120) having at least one reflection surface (1211a, 1211b) facing the predetermined space; and a light receiving unit (115) that receives laser light obtained through multiple reflections by the at least one reflection surface (1211a, 1211b). The at least one reflection surface (1211a, 1211b) is arranged so as to cause intersections and multiple reflections of the laser light in the predetermined space as viewed from the traveling direction of the sound.

Description

[Technical Field]

[0001] The present disclosure relates to a sound measuring instrument. [Background Art]

[0002] As a device that collects sound waves propagating in air and converts them into electrical signals, a diaphragm-type microphone is known, which allows sound waves to enter the diaphragm and converts minute vibrations excited in the diaphragm by sound into electrical signals. However, since it is difficult for a diaphragm-type microphone to detect sound with a frequency higher than the mechanical resonance frequency of the diaphragm, the upper limit of the detectable sound frequency band is limited to approximately 100 kHz.

[0003] On the other hand, optical microphones that measure minute, high-speed vibrations using light represented by laser light are known. For example, Patent Document 1 discloses a sound collection system that measures sound pressure by directly propagating laser light into a sound field and directly capturing changes in refractive index caused by sound waves in air using a laser Doppler vibrometer. In the sound collection system described in Patent Document 1, since the mechanical resonance of the diaphragm is not used for sound detection, the upper limit of the detectable sound frequency band easily exceeds 100 kHz. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2004-279259 [Summary of Invention] [Problem to be Solved by the Invention]

[0005] However, the sound collection system described in Patent Document 1 has low sound pressure sensitivity.

[0006] Therefore, the present disclosure provides a sound measuring instrument with improved sound pressure sensitivity. [Means for Solving the Problem]

[0007] A sound measuring instrument according to one aspect of the present disclosure comprises a light source that emits laser light, a frame that surrounds a predetermined space through which sound passes so as to intersect with the direction of sound propagation and has at least one reflective surface directed toward the predetermined space, and a light receiving unit that receives the laser light obtained by multiple reflection by the at least one reflective surface, wherein the at least one reflective surface is arranged such that, when the predetermined space is viewed from the direction of sound propagation, the laser light intersects and undergoes multiple reflection in the predetermined space. The frame portion is configured such that, when viewed from the direction of sound propagation, the ratio between the horizontal width of the frame portion and the vertical width of the frame portion is changed, thereby adjusting the directivity of the sound measuring instrument. . Alternatively, a sound measuring instrument according to one aspect of the present disclosure comprises a light source that emits laser light, a frame that surrounds a predetermined space through which sound passes so as to intersect with the direction of sound propagation and has at least one reflective surface directed toward the predetermined space, and a light receiving unit that receives the laser light obtained by multiple reflection by the at least one reflective surface, wherein the at least one reflective surface is arranged to cause the laser light to intersect and multiple reflect in the predetermined space when the predetermined space is viewed from the direction of sound propagation, and the frame is adjusted so that the horizontal and vertical directivity of the sound measuring instrument are different when the frame is viewed from the direction of sound propagation by increasing at least one of the horizontal width and vertical width of the frame. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide a sound measuring instrument with improved sound pressure sensitivity. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a diagram illustrating an example of a conventional optical microphone configuration. [Figure 2] Figure 2 shows an example of the configuration of a sound measuring instrument according to an embodiment. [Figure 3] Figure 3 is a perspective view of the frame shown in Figure 2, viewed from an oblique direction. [Figure 4] Figure 4 is a diagram illustrating an example of the configuration of the measurement unit shown in Figure 2. [Figure 5] Figure 5 shows another example of the configuration of the sound measuring instrument according to the embodiment. [Figure 6] Figure 6 shows the results of Experimental Example 1. [Figure 7] Figure 7 shows the results of Experiment Example 2. [Figure 8] Figure 8 shows the results of Experiment Example 3. [Figure 9] Figure 9 shows an example of the configuration of a sound measuring instrument according to Modification 1. [Figure 10] Figure 10 shows an example of the configuration of a sound measuring instrument according to Modification 2. [Figure 11]FIG. 11 is a diagram illustrating an example of a configuration of a sound measuring instrument according to Modification 3. [Figure 12] FIG. 12 is a diagram illustrating an example of a configuration of a sound measuring instrument according to Modification 4. [Figure 13] FIG. 13 is a diagram illustrating an example of a configuration of a sound measuring instrument according to Modification 5. [Figure 14] FIG. 14 is a diagram illustrating a first example of a relationship between a ratio of a horizontal width to a vertical width of a frame portion when the frame portion is viewed from a sound traveling direction, and directivity of the sound measuring instrument. [Figure 15] FIG. 15 is a diagram illustrating a second example of a relationship between a ratio of a horizontal width to a vertical width of a frame portion when the frame portion is viewed from a sound traveling direction, and directivity of the sound measuring instrument. DESCRIPTION OF EMBODIMENTS

[0010] (Findings Leading to the Present Disclosure) In recent years, techniques for detecting inaudible sound that cannot be detected by the human ear have been applied to detect or predict abnormalities in equipment and the like. Inaudible sound is sound in the ultrasonic band, and is less susceptible to the influence of audible sound, so abnormalities in equipment can be detected earlier with inaudible sound than with audible sound.

[0011] However, sound in the ultrasonic band of 100 kHz or higher cannot be detected by diaphragm-type microphones, so application of optical microphones is expected. Since optical microphones do not use mechanical resonance of a diaphragm for sound detection, they can detect sound in a frequency band of 100 kHz or higher. However, optical microphones have lower sound pressure sensitivity than diaphragm-type microphones, and for example, there are cases where sound cannot be detected unless it has a sound pressure of 80 dB or higher.

[0012] Hereinafter, an example of a conventional optical microphone will be described with reference to FIG. 1. FIG. 1 is a diagram for explaining an example of a configuration of a conventional optical microphone. The optical microphone 1 shown in FIG. 1 has the same configuration as the sound collection system described in Patent Document 1. FIG. 1 shows a schematic cross-sectional view when the frame portion 20 is cut along the ZX plane. . light The microphone 1 includes, for example, a laser Doppler vibrometer 10, a frame portion 20 constituted by a pair of reflecting mirrors 21a, 21b and an angle adjusting reflecting mirror 22, and a calculation unit 30. The pair of reflecting mirrors 21a and 21b each have one reflecting surface 211a and 211b directed toward a predetermined space W through which sound passes (that is, the predetermined space W in the sound field). The direction in which sound passes is indicated by a hollow arrow, but may be the Y-axis direction. The laser Doppler vibrometer 10 emits laser light into the predetermined space W, and reads the Doppler phenomenon caused by the interference between the reflected and returned laser light and reference light, thereby measuring the sound pressure in the predetermined space W from the phase fluctuation of the laser light caused by the change in the refractive index of air. At this time, as shown in FIG. 1, the laser light is reflected a plurality of times between the pair of reflecting mirrors 21a and 21b (in other words, multiple reflection), reflected by the reflecting surface 221 of the angle adjusting reflecting mirror 22, and returns to the laser Doppler vibrometer 10.

[0013] In order to improve the sound pressure sensitivity of the optical microphone 1, it is considered effective to increase the optical path length of the laser light in the sound field. However, in the optical microphone 1, when the predetermined space W is expanded to increase the optical path length, the laser light is affected by both the positive pressure and negative pressure of the sound wave, so the sound pressure sensitivity may decrease. For example, in the optical microphone 1 shown in FIG. 1, the predetermined space W can be expanded by expanding the distance between the pair of reflecting mirrors 21a and 21b arranged in parallel and expanding these reflecting mirrors 21a and 21b vertically or horizontally. However, when the predetermined space W is expanded, both the positive pressure and negative pressure of the sound wave are included in the predetermined space W, which may lead to a decrease in sound pressure sensitivity. Further, for example, in the optical microphone 1, by reducing the incident angle of the laser light, the laser light can be subjected to multiple reflections to increase the optical path length of the laser light. However, even a slight vibration makes it easier for the laser light to hit the edge of the reflecting mirror, so the sound pressure sensitivity may decrease.

[0014] Therefore, the inventors of this application, after diligently studying the above problems, found that it is possible to extend the optical path length of the laser light in a predetermined space W without expanding the predetermined space W. As a result, they found that it is possible to obtain a sound measuring instrument (a so-called optical microphone) with improved sound pressure sensitivity.

[0015] Therefore, according to this disclosure, it is possible to provide a sound measuring instrument with improved sound pressure sensitivity.

[0016] (Summary of this disclosure) An overview of one aspect of this disclosure is as follows:

[0017] A sound measuring instrument according to one aspect of the present disclosure comprises a light source that emits laser light, a frame that surrounds a predetermined space through which sound passes so as to intersect with the direction of sound propagation and has at least one reflective surface directed toward the predetermined space, and a light receiving unit that receives the laser light obtained by multiple reflection by the at least one reflective surface, wherein the at least one reflective surface is arranged such that the laser light intersects and is multiplely reflected in the predetermined space when the predetermined space is viewed from the direction of sound propagation.

[0018] This allows the sound measuring instrument to extend the optical path length of the laser beam within a given space, thereby improving its sound pressure sensitivity.

[0019] For example, in a sound measuring instrument according to one aspect of the present disclosure, the at least one reflective surface may be formed of at least one concave or flat surface.

[0020] This makes it easier for the sound measuring instrument to adjust the optical path length of the laser beam within a given space to a desired length. Furthermore, for example, the sound measuring instrument can also adjust the size of the given space and the optical path length of the laser beam according to the location where the sound measuring instrument is installed, the size of the installation location, or the characteristics of the sound being measured (e.g., frequency or sound pressure).

[0021] For example, in a sound measuring instrument according to one aspect of the present disclosure, the at least one reflective surface may be formed in a series.

[0022] This allows the sound measuring instrument to have a series of smooth reflective surfaces, thus providing a large area for reflecting laser light. Consequently, the sound measuring instrument makes it easier for the user to design the optical path of the laser beam and reduces losses caused by the laser beam escaping from the reflective surface.

[0023] For example, in a sound measuring instrument according to one aspect of the present disclosure, the at least one reflective surface may be a plurality of reflective surfaces, and the orientation of each of the plurality of reflective surfaces may differ within the predetermined space.

[0024] This allows the sound measuring instrument to intersect and reflect laser light in multiple different directions within a given space, thereby easily extending the optical path length within that space.

[0025] For example, in a sound measuring instrument according to one aspect of the present disclosure, the shape of the frame may be a polygon having three or more sides when viewed from the direction of sound propagation.

[0026] This allows the sound measuring instrument to appropriately set the size and shape of a predetermined space, or the optical path length of the laser beam, etc., according to, for example, the location where the sound measuring instrument is installed, the size of the installation location, or the characteristics of the sound being measured, thereby enabling more accurate sound measurement.

[0027] For example, in a sound measuring instrument according to one aspect of the present disclosure, the shape of the polygon may be triangular, quadrilateral, pentagonal, or hexagonal.

[0028] This allows the sound measuring instrument to properly reflect the laser light and measure sound accurately.

[0029] For example, in a sound measuring instrument according to one aspect of the present disclosure, the frame portion is composed of at least one reflective member, the at least one reflective member is a plurality of reflective members, and the plurality of reflective members may be spaced apart from each other.

[0030] This allows the sound measuring instrument to easily adjust the installation angles of multiple reflective members. Consequently, the sound measuring instrument can easily adjust the optical path length of the laser beam within a given space.

[0031] For example, in a sound measuring instrument according to one aspect of the present disclosure, the frame portion is composed of at least one reflective member, and the at least one reflective member may be one reflective member.

[0032] This allows sound measuring instruments to measure sound more easily. For example, a sound measuring instrument only requires the installation of a frame made up of one reflective member, eliminating the need to adjust the relative positions of reflective members, as is required with frames made up of two or more reflective members.

[0033] For example, a sound measuring instrument according to one aspect of the present disclosure may further include a collimating lens, and the light source may cause the laser light to be incident on the predetermined space through the collimating lens.

[0034] As a result, the sound measuring instrument is less likely to lose its laser beam diameter while the laser light is undergoing multiple reflections within a given space, thus preventing the laser light from straying beyond the reflective surface. Therefore, the sound measuring instrument can reduce the loss of laser light, improving its sound pressure sensitivity.

[0035] For example, a sound measuring instrument according to one aspect of the present disclosure may further include at least one angle-adjusting reflective member that reflects the laser light and is capable of adjusting the reflection angle of the laser light.

[0036] This allows the sound measuring instrument to adjust the reflection angle of the laser beam and thus adjust the optical path of the laser beam.

[0037] For example, in a sound measuring instrument according to one aspect of the present disclosure, the at least one angle-adjusting reflective member may be arranged independently of the frame.

[0038] This allows the sound measuring instrument to precisely adjust the angle of the laser beam and the optical path of the laser beam.

[0039] For example, in a sound measuring instrument according to one aspect of the present disclosure, the at least one angle-adjusting reflective member may be fixedly arranged on the frame.

[0040] This allows the sound measuring instrument to stabilize the angle of the laser beam without fluctuation. Furthermore, the configuration is simplified.

[0041] These comprehensive or specific embodiments may be implemented as systems, methods, apparatus, integrated circuits, computer programs, or recording media such as computer-readable CD-ROMs, or as any combination of systems, methods, apparatus, integrated circuits, computer programs, and recording media.

[0042] The embodiments of this disclosure will be described in detail below with reference to the drawings. The numerical values, shapes, materials, components, arrangement and connection configurations of components, steps, and the order of steps shown in the following embodiments are examples and are not intended to limit the scope of the claims. Furthermore, among the components in the following embodiments, components that are not described in the independent claim representing the highest-level concept will be described as optional components. In addition, the figures are not necessarily strictly illustrative. In each figure, substantially identical components are denoted by the same reference numerals, and redundant explanations may be omitted or simplified.

[0043] Furthermore, in this disclosure, terms indicating relationships between elements such as parallel and perpendicular, terms indicating the shape of elements such as rectangles, and numerical values ​​do not represent only strict meanings, but also include substantially equivalent ranges, such as differences of a few percent.

[0044] (Embodiment) The embodiments will be described in detail below with reference to the drawings.

[0045] [1. Structure] First, the configuration of the sound measuring instrument according to the embodiment will be described. Figure 2 is a diagram showing an example of the configuration of the sound measuring instrument 100 according to the embodiment. Figure 3 is a perspective view of the frame portion 120 shown in Figure 2, viewed from an oblique direction.

[0046] As shown in Figure 2, the sound measuring instrument 100 includes, for example, a measuring unit 110, a frame unit 120, and a calculation unit 130. Each of these components will be described below.

[0047] [Frame body part 120] The frame portion 120 is composed of at least one reflective member that surrounds a predetermined space through which sound passes, intersecting with the direction of sound propagation. In the examples of Figures 2 and 3, the sound measuring instrument 100 measures sound traveling from the positive Y-axis direction toward the ZX-plane in the predetermined space. Surrounding the predetermined space intersecting with the direction of sound propagation does not mean completely surrounding the predetermined space, but also includes surrounding a part of the predetermined space with at least one reflective member. Furthermore, if a pair of reflective members are arranged parallel to each other, it also includes sandwiching the sound between the pair of reflective members.

[0048] In this embodiment, the frame portion 120 is composed of two reflective members 121a and 121b, which are spaced apart from each other. In this case, the frame portion 120 may have at least one gap between the two reflective members 121a and 121b. The at least one gap is, for example, a gap for injecting laser light into a predetermined space (hereinafter also referred to as the inlet), and a gap for adjusting the reflection angle of the laser light and returning it to the inlet (hereinafter also referred to as the angle adjustment opening). The frame portion 120 may be provided with an angle adjustment reflective member 122 inside the angle adjustment opening or outside the angle adjustment opening (negative Z-axis side). The angle adjustment reflective member 122 has a reflective surface 1221, which is positioned so that the reflective surface 1221 faces the predetermined space. The angle-adjusting reflective member 122 may be rotatably mounted on a support shaft (not shown) fixed to two reflective members 121a and 121b, for example, or it may be tiltably supported by a piezoelectric element. This allows the angle-adjusting reflective member 122 to adjust the reflection angle of the laser beam with respect to the reflective surface 1221, thereby enabling the laser beam to be returned to the measuring unit 110 with high accuracy.

[0049] The shape of the frame portion 120 may be triangular, square, pentagonal, hexagonal, circular, or elliptical when viewed from the direction of sound propagation. In this case, the shape of the frame portion 120 is square.

[0050] The dimensions of the frame section 120 may be set appropriately according to the design. For example, the width (length in the X-axis direction) and height (length in the Z-axis direction) may each be 130 mm, and the depth (length in the Y-axis direction) may be 20 mm.

[0051] Each of the two reflective members 121a and 121b has at least one reflective surface. For example, as shown in Figure 3, each of the two reflective members 121a and 121b has multiple reflective surfaces 1211a and 1211b, and these multiple reflective surfaces 1211a and 1211b are arranged to face a predetermined space. More specifically, the two reflective surfaces 1211a and 1211b are arranged to cause multiple reflections of laser light in the predetermined space when the predetermined space is viewed from the direction of sound propagation (i.e., the Y-axis direction). For example, each of the multiple reflective surfaces 1211a is planar and is formed in a series. Furthermore, the orientation of each of the multiple reflective surfaces 1211a is different within the predetermined space. The multiple reflective surfaces 1211a may differ in shape and area. For example, the shape of the reflective surface 1211a may be a square, rectangle, or trapezoid, and its area may differ depending on its position on the reflective member 121a (e.g., corners and edges). The same applies to multiple reflective surfaces 1211b as to multiple reflective surfaces 1211a.

[0052] Furthermore, the multiple reflective surfaces 1211a of the reflective member 121a are such that two adjacent continuous reflective surfaces 1211a form a recess and a convex portion, and in this case, the angle between two adjacent reflective surfaces 1211a should be a right angle (tolerance: ±0.01). Also, each of the multiple reflective surfaces 1211a is a plane, and in this case, the surface accuracy of each reflective surface 1211a should be 4λ or less. In addition, each reflective surface 1211a should have a reflectance of 90% or more at the wavelength of the laser light used. The same applies to the multiple reflective surfaces 1211b as to the multiple reflective surfaces 1211a.

[0053] Although the multiple reflective surfaces 1211a are formed in a continuous sequence, they do not necessarily have to be formed in a continuous sequence.

[0054] For example, if multiple reflective surfaces 1211a are formed in a series, the reflective member 121a may be manufactured by forming a base (or substrate) from a substrate such as glass, metal, ceramics, or resin, and then forming a metal reflective film, an enhanced reflective film, a dielectric single layer film, a dielectric multilayer film, or a protective film on the multiple surfaces that will become the multiple reflective surfaces 1211a. The base (or substrate) may be formed by, for example, a known manufacturing method such as a frame. The metal reflective film is a film for reflecting laser light and is formed from a metallic material such as silver or aluminum. The enhanced reflective film may be composed of a dielectric multilayer film or may be formed on the metal reflective film. The protective film is formed on the metal reflective film and physically or chemically protects the metal reflective film. Alternatively, the reflective member 121a may be manufactured by mirror-finishing a metal such as aluminum, stainless steel, brass, iron, or titanium.

[0055] On the other hand, if the multiple reflective surfaces 1211a are not formed in a continuous sequence, the reflective member 121a may be manufactured by attaching reflectors to multiple surfaces that will become the multiple reflective surfaces 1211a. The reflectors are not particularly limited, and only need to have a reflective surface that has a reflectivity of 90% or more of the laser light used. For example, the reflectors may be mirrors made by depositing a highly reflective metal or dielectric thin film such as aluminum, gold, or silver onto a glass substrate, or mirror-finished metal plates.

[0056] In addition, although the multiple reflective surfaces 1211b are formed in a continuous sequence, similar to the multiple reflective surfaces 1211a, they do not necessarily have to be formed in a continuous sequence. In this case, the reflective member 121b is manufactured in the same manner as the reflective member 121a.

[0057] [Measurement unit 110] The measurement unit 110 emits laser light into a predetermined space and measures the sound pressure in that space based on the phase variation of the laser light (hereinafter also referred to as reflected light) that is reflected within the predetermined space surrounded by the reflecting members 121a and 121b and returns to the measurement unit 110. The measurement unit 110 is, for example, a laser Doppler vibrometer or a photodiode. When the measurement unit 110 is a laser Doppler vibrometer, the measurement unit 110 has, for example, the configuration shown in Figure 4. Figure 4 is a diagram illustrating an example of the configuration of the measurement unit 110 shown in Figure 2.

[0058] As shown in Figure 4, the measurement unit 110 has a light source 111 that emits laser light, and the laser light output from the light source is spectrally split into two directions by the first beam splitter 112a. One of the laser beams L1 (so-called emitted light) spectrally split into two directions is emitted after passing through the second beam splitter 112b. On the other hand, the other laser beam L2 spectrally split by the first beam splitter 112a has its optical axis adjusted by the mirror 113 and is incident on the AOM (Acoust-Optic Modulator) 114b, which is driven by the AOM driver 114a, and a reference light with a shifted laser frequency is output from the AOM 114b. The reference light is optically adjusted to pass through the third beam splitter 112c and irradiate the light receiving unit 115 (for example, a photodetector). Furthermore, the laser light L3 (so-called reflected light) that is reflected back from a predetermined space is irradiated onto the light receiving unit 115 via the second beam splitter 112b and the third beam splitter 112c, and is superimposed with the reference light to become interference light which is received by the light receiving unit 115. The measurement unit 110 detects the phase variation of the laser light caused by this superposition interference using the detection circuit 116 and outputs it as an analog signal.

[0059] [Calculation unit 130] The calculation unit 130 calculates the sound pressure in a predetermined space based on the signal output from the measurement unit 110. For example, the calculation unit 130 may be a frequency analyzer.

[0060] While a laser Doppler vibrometer was described as an example of the measurement unit 110 housing the light source 111 and the light receiving unit 115 within a single housing, the measurement unit is not limited to this. Furthermore, the measurement unit 110 may house the light source 111 and the light receiving unit 115 in separate housings. Also, not only the light source 111 and the light receiving unit 115, but also the first beam splitter 112a, second beam splitter 112b, third beam splitter 112c, AOM 114b, and mirror 113, etc., do not necessarily have to be included in a single housing.

[0061] The light source 111 may be, for example, a He-Ne laser oscillator or a laser diode.

[0062] [Collimating Lens 140] The sound measuring instrument 100 may further include a collimating lens 140 (see Figure 5). Figure 5 shows another example of the configuration of the sound measuring instrument 100 according to the embodiment.

[0063] As shown in Figure 5, the light source 111 (see Figure 4) causes laser light to enter a predetermined space via the collimating lens 140. This prevents even a slight widening of the laser beam diameter while the laser light is reflected within the predetermined space, thus reducing the amount of laser light that extends beyond the reflective surfaces 1211a and 1211b. As a result, the loss of reflected light received by the measurement unit 110 is reduced, and the sound pressure sensitivity of the sound measuring instrument 100 is improved.

[0064] [2. Experimental Examples] The following describes the simulations performed on the sound measuring instrument 100 according to the embodiment and their results.

[0065] [Experimental Example 1] In Experimental Example 1, the effect of focal length on suppressing beam divergence of laser light was simulated using collimating lenses with different focal lengths. The beam diameter was calculated based on Gaussian beam propagation theory. The results are shown in Figure 6.

[0066] Figure 6 shows the results of Experimental Example 1. Figure 6 shows the relationship between the focal length f (mm) of the collimating lens, the distance from the collimating lens (so-called optical path length) (m), and the beam diameter (mm) of the laser light emitted through the collimating lens, using 13 collimating lenses with different focal lengths. Sex It is shown.

[0067] As shown in Figure 6, it was found that the shorter the focal length, the shorter the distance over which the laser beam can remain parallel. Simulation results showed that using a collimating lens with a focal length of 150 mm suppresses the beam divergence of the laser beam, and the laser beam remains parallel for optical path lengths up to 5 m from the lens.

[0068] The simulation results confirmed that the light source 111 can maintain parallelism by directing the laser beam into a predetermined space via the collimating lens 140. Therefore, it was confirmed that the sound pressure sensitivity of the sound measuring instrument 100 can be further improved by adding the collimating lens 140.

[0069] [Experimental Example 2] Next, in Experimental Example 2, the sound pressure sensitivity of a sound measuring instrument was simulated when the sound wave was a plane wave. In Experimental Example 2, a conventional optical microphone 1 shown in Figure 1 and a sound measuring instrument 100 shown in Figure 2 were used.

[0070] In optical microphone 1, when the laser beam was reflected 10 times between a pair of planar reflective mirrors (reflectors 21a and 21b in Figure 1), the optical path length was 2 m.

[0071] In the sound measuring instrument 100, when laser light was reflected multiple times between a pair of uneven reflective mirrors (reflective members 121a and 121b in Figure 2), the optical path length was 4 m. The results are shown in Figure 7.

[0072] Figure 7 shows the results of Experimental Example 2. In Figure 7, the sound pressure level was calculated as the relative sound pressure level (dB) when the sound pressure at an optical path length of 1m was set to 0dB.

[0073] As shown in Figure 7, the relative sound pressure level of the sound measured by the optical microphone 1 was 6 dB. The relative sound pressure level of the sound measured by the sound measuring instrument 100 was 12 dB. Therefore, it was confirmed that the sound measuring instrument 100 according to Embodiment 1 has improved sound pressure sensitivity compared to the optical microphone 1.

[0074] [Experimental Example 3] Next, in Experiment Example 3, the sound pressure sensitivity of a sound measuring instrument was simulated when the sound wave was a spherical wave. Specifically, in Experiment Example 3, the simulation was performed with a distance of 1m from the sound source to the frame parts 20 and 120 (also called the sound receiving parts). In Experiment Example 3, the same points as in Experiment Example 2 are omitted, and the differences are described. The results are shown in Figure 8.

[0075] Figure 8 shows the results of Experimental Example 3. In Figure 8, the sound pressure level was calculated as the relative sound pressure level (dB) with 0 Hz of the sound measuring instrument 100 set to 0 dB. Figure 8 also shows the relative sound pressure level, which is the effective value of the integral of the sound pressure along the optical path in the time direction, for each frequency.

[0076] As shown in Figure 8, the relative sound pressure level of the sound measured by the sound measuring instrument 100 was higher than the relative sound pressure level of the sound measured by the optical microphone 1. The maximum relative sound pressure level difference was 7.93 dB (230 kHz). Therefore, it was confirmed that the sound measuring instrument 100 according to Embodiment 1 has improved sound pressure sensitivity compared to the optical microphone 1.

[0077] [3. Effects, etc.] As described above, the sound measuring instrument 100 according to the embodiment comprises a light source 111 that emits laser light, a frame portion 120 that surrounds a predetermined space through which sound passes so as to intersect with the direction of sound propagation and has at least one reflective surface 1211a, 1211b directed toward the predetermined space, and a light receiving portion 115 that receives the laser light obtained by multiple reflection by the at least one reflective surface 1211a, 1211b, wherein the at least one reflective surface 1211a, 1211b is arranged so as to cause multiple reflections of the laser light in the predetermined space when the predetermined space is viewed from the direction of sound propagation.

[0078] As a result, the sound measuring instrument 100 can extend the optical path length of the laser beam within a predetermined space, thereby improving its sound pressure sensitivity.

[0079] For example, in the sound measuring instrument 100 according to the embodiment, at least one reflective surface 1211a, 1211b may be formed of at least one concave surface or a flat surface.

[0080] This makes it easier for the sound measuring instrument 100 to adjust the optical path length of the laser beam within a predetermined space to a desired length. Furthermore, for example, the sound measuring instrument 100 can also adjust the size of the predetermined space and the optical path length of the laser beam according to the location where the sound measuring instrument 100 is installed, the size of the installation location, or the characteristics of the sound being measured (e.g., frequency or sound pressure).

[0081] For example, in the sound measuring instrument 100 according to the embodiment, at least one reflective surface 1211a, 1211b may be formed in a continuous sequence.

[0082] As a result, the sound measuring instrument 100 can have a series of smooth reflective surfaces, allowing for a larger area to reflect the laser light. Therefore, with the sound measuring instrument 100, the user can more easily design the optical path of the laser light and reduce losses caused by the laser light escaping from the reflective surface.

[0083] For example, in the sound measuring instrument 100 according to the embodiment, at least one reflective surface 1211a, 1211b is a plurality of reflective surfaces, and the orientation of each of the plurality of reflective surfaces may be different within a predetermined space.

[0084] As a result, the sound measuring instrument 100 can reflect laser light in multiple different directions within a predetermined space, thereby easily extending the optical path length within that space.

[0085] For example, in the sound measuring instrument 100 according to the embodiment, the shape of the frame portion 120 may be a polygon having three or more sides when viewed from the direction of sound propagation.

[0086] As a result, the sound measuring instrument 100 can appropriately set the size and shape of a predetermined space, or the optical path length of the laser beam, etc., according to, for example, the location where the sound measuring instrument 100 is installed, the size of the installation location, or the characteristics of the sound being measured, thereby enabling more accurate sound measurement.

[0087] For example, in the sound measuring instrument 100 according to the embodiment, the polygonal shape may be triangular, quadrilateral, pentagonal, or hexagonal.

[0088] This allows the sound measuring instrument to properly reflect the laser light and measure sound accurately.

[0089] For example, in the sound measuring instrument 100 according to the embodiment, the frame portion 120 is composed of at least one reflective member 121a, 121b, and the at least one reflective member 121a, 121b is a plurality of reflective members, and the plurality of reflective members 121a, 121b may be spaced apart from each other.

[0090] This allows the sound measuring instrument 100 to easily adjust the installation angles of the multiple reflective members 121a and 121b. Therefore, the sound measuring instrument 100 can easily adjust the optical path length of the laser beam within a predetermined space.

[0091] For example, in the sound measuring instrument 100 according to the embodiment, the frame portion 120 is composed of at least one reflective member 121a, 121b, and the at least one reflective member 121a, 121b may be a single reflective member.

[0092] This allows the sound measuring instrument 100 to measure sound more easily. For example, the sound measuring instrument only requires the installation of a frame made up of one reflective member, eliminating the need to adjust the relative positions of the reflective members, as is the case with a frame made up of two or more reflective members.

[0093] For example, the sound measuring instrument 100 according to the embodiment may further include a collimating lens, and the light source may be a laser beam incident into a predetermined space through the collimating lens.

[0094] As a result, the sound measuring instrument 100 is less likely to lose its beam diameter while the laser light is undergoing multiple reflections within a predetermined space, thus preventing the laser light from extending beyond the reflective surface. Therefore, the sound measuring instrument 100 can reduce the loss of laser light, thereby improving its sound pressure sensitivity.

[0095] For example, the sound measuring instrument 100 according to the embodiment may further include at least one angle-adjusting reflective member 122 that reflects laser light and allows adjustment of the reflection angle of the laser light.

[0096] This allows the sound measuring instrument 100 to adjust the reflection angle of the laser beam and adjust the optical path of the laser beam.

[0097] For example, in the sound measuring instrument 100 according to the embodiment, at least one angle-adjusting reflective member 122 may be arranged independently of the frame portion 120.

[0098] This allows the sound measuring instrument 100 to finely adjust the angle of the laser beam and precisely adjust the optical path of the laser beam.

[0099] For example, in a sound measuring instrument 100 according to one aspect of the present disclosure, at least one angle-adjusting reflective member 122 may be fixedly positioned on the frame portion 120.

[0100] This allows the sound measuring instrument 100 to stabilize the angle of the laser beam without fluctuation. Furthermore, the configuration is simplified.

[0101] (Variation 1) [1. Structure] Next, the configuration of the sound measuring instrument according to Modification 1 will be described. Figure 9 is a diagram showing an example of the configuration of the sound measuring instrument 100a according to Modification 1.

[0102] The sound measuring instrument 100 according to the embodiment was shown to have two reflective members 121a and 121b having an uneven reflective surface in which a plurality of planar reflective surfaces are formed in a series. However, the sound measuring instrument 100a according to Modification 1 differs from the embodiment in that it has four reflective members 221a, 221b, 221c, and 221d, each having a single planar reflective surface. The differences from the embodiment will be explained below.

[0103] The four reflective members 221a, 221b, 221c, and 221d each have one reflective surface 2211a, 2211b, 2211c, and 2211d. These reflective surfaces are planar and oriented toward a predetermined space.

[0104] In addition, in the sound measuring instrument 100a, the reflective members 221a and 221c are arranged in parallel, and the reflective members 221b and 221d are arranged in parallel.

[0105] Furthermore, the frame portion 120a is equipped with two angle-adjusting reflective members 222a and 222b. The angle-adjusting reflective member 222a adjusts the reflection angle of the laser light reflected by the reflective surface 2221a by adjusting the orientation of the reflective surface 2221a. In other words, the angle-adjusting reflective member 222a is used to return the laser light to the measuring unit 110. The angle-adjusting reflective member 222b reflects the laser light that has been multiple-reflected in the Z-axis direction between the pair of reflective members 221b and 221d back towards the reflective member 221a at the reflective surface 2221b. As a result, the laser light is multiple-reflected in the X-axis direction between the pair of reflective members 221a and 221c.

[0106] The sound measuring instrument 100a according to Modification 1, having the above configuration, can cause multiple reflections of laser light vertically and horizontally within a predetermined space, thereby extending the optical path length without changing the size of the sound receiving section.

[0107] Note that the angle-adjusting reflective members 222a and 222b do not necessarily have to be arranged independently of the reflective members 221a to 221d. For example, the angle-adjusting reflective member 222a may be fixed to the reflective member 221b or the reflective member 221c. Also, for example, the angle-adjusting reflective member 222b may be fixed to the reflective member 221c or the reflective member 221d.

[0108] [2. Effects, etc.] As described above, the sound measuring instrument 100a according to the embodiment comprises a light source 111 (see Figure 4) that emits laser light, a frame portion 120a that surrounds a predetermined space through which sound passes so as to intersect with the direction of sound propagation and has at least one reflective surface 2211a, 2211b, 2211c, 2211d directed toward the predetermined space, and a light receiving portion 115 (see Figure 4) that receives the laser light obtained by multiple reflection by the at least one reflective surface 2211a, 2211b, 2211c, 2211d, wherein the at least one reflective surface 2211a, 2211b, 2211c, 2211d is arranged to cause multiple reflections of the laser light in the predetermined space when the predetermined space is viewed from the direction of sound propagation.

[0109] As a result, the sound measuring instrument 100a can extend the optical path length of the laser beam within a predetermined space, thereby improving its sound pressure sensitivity.

[0110] For example, in the sound measuring instrument 100a according to the embodiment, at least one reflective surface 2211a, 2211b, 2211c, 2211d may be formed of at least one concave surface or flat surface.

[0111] This makes it easier for the sound measuring instrument 100a to adjust the optical path length of the laser beam within a predetermined space to a desired length. Furthermore, for example, the sound measuring instrument 100a can also adjust the size of the predetermined space and the optical path length of the laser beam according to the location where the sound measuring instrument 100a is installed, the size of the installation location, or the characteristics of the sound being measured (e.g., frequency or sound pressure).

[0112] For example, in the sound measuring instrument 100a according to the embodiment, at least one reflective surface 2211a, 2211b, 2211c, 2211d may be formed in a series.

[0113] As a result, the sound measuring instrument 100a can have a series of smooth reflective surfaces, thus allowing for a larger area to reflect the laser light. Therefore, with the sound measuring instrument 100a, the user can more easily design the optical path of the laser light and reduce losses caused by the laser light escaping from the reflective surface.

[0114] For example, in the sound measuring instrument 100a according to the embodiment, at least one reflective surface 2211a, 2211b, 2211c, 2211d is a plurality of reflective surfaces, and the orientation of each of the plurality of reflective surfaces may be different within a predetermined space.

[0115] As a result, the sound measuring instrument 100a can intersect and reflect laser light in multiple different directions within a predetermined space, thereby easily extending the optical path length within that space.

[0116] For example, in the sound measuring instrument 100a according to the embodiment, the shape of the frame portion 120a may be a polygon having three or more sides when viewed from the direction of sound propagation.

[0117] As a result, the sound measuring instrument 100a can appropriately set the size and shape of a predetermined space, or the optical path length of the laser beam, etc., according to, for example, the location where the sound measuring instrument 100a is installed, the size of the installation location, or the characteristics of the sound being measured, thereby enabling more accurate sound measurement.

[0118] For example, in the sound measuring instrument 100a according to the embodiment, the shape of the polygon may be triangular, quadrilateral, pentagonal, or hexagonal.

[0119] As a result, the sound measuring instrument 100a can properly reflect the laser light and measure sound accurately.

[0120] For example, in the sound measuring instrument 100a according to the embodiment, the frame portion 120 is composed of at least one reflective member 221a, 221b, 221c, 221d, and the at least one reflective member 221a, 221b, 221c, 221d is a plurality of reflective members, and the plurality of reflective members 221a, 221b, 221c, 221d may be spaced apart from each other.

[0121] This allows the sound measuring instrument 100a to easily adjust the installation angles of the multiple reflective members 221a, 221b, 221c, and 221d. Therefore, the sound measuring instrument 100a can easily adjust the optical path length of the laser beam within a predetermined space.

[0122] For example, the sound measuring instrument 100a according to the embodiment may further include at least one angle-adjusting reflective member (222a, 222b) that reflects laser light and allows adjustment of the reflection angle of the laser light.

[0123] This allows the sound measuring instrument 100a to adjust the reflection angle of the laser beam and adjust the optical path of the laser beam.

[0124] For example, in the sound measuring instrument 100a according to the embodiment, at least one angle-adjusting reflective member (222a, 222b) may be arranged independently of the frame portion 120a.

[0125] This allows the sound measuring instrument 100a to finely adjust the angle of the laser beam and precisely adjust the optical path of the laser beam.

[0126] For example, in a sound measuring instrument 100a according to one aspect of the present disclosure, at least one angle-adjusting reflective member (222a, 222b) may be fixedly arranged on the frame portion 120a.

[0127] This allows the sound measuring instrument 100a to stabilize the angle of the laser beam without fluctuation. Furthermore, the configuration is simplified.

[0128] (Modification 2) [1. Structure] Next, the configuration of the sound measuring instrument according to Modification 2 will be described. Figure 10 shows an example of the configuration of the sound measuring instrument 100b according to Modification 2.

[0129] The sound measuring instrument 100a according to Modification 1 comprises four reflective members 221a, 221b, 221c, and 221d having planar reflective surfaces, and an example is shown where reflective member 221a and reflective member 221c are arranged parallel to each other. The sound measuring instrument 100b according to Modification 2 differs from Modification 1 in that the four reflective members 321a, 321b, 321c, and 321d having planar reflective surfaces are arranged to surround a predetermined space in a triangle when viewed from the direction of sound propagation. The following describes the embodiment and the differences from Modification 1.

[0130] The four reflective members 321a, 321b, 321c, and 321d each have one reflective surface 3211a, 3211b, 3211c, and 3211d. These reflective surfaces are planar and oriented toward a predetermined space. Furthermore, the frame portion 120b includes one angle-adjusting reflective member 322. The angle-adjusting reflective member 322 adjusts the reflection angle of the laser beam on the reflective surface 3221 by adjusting the orientation of the reflective surface 3221. In other words, the angle-adjusting reflective member 322 is used to return the laser beam to the measuring unit 110.

[0131] The sound measuring instrument 100b according to the modified example 2 has the above configuration, which allows for multiple reflections of laser light in three directions within a predetermined space, thereby extending the optical path length without changing the size of the sound receiving section.

[0132] The angle-adjusting reflective member 322 does not necessarily have to be positioned independently of the reflective members 321a and 321b. For example, the angle-adjusting reflective member 322 may be fixed to the reflective member 321a or the reflective member 321b.

[0133] [2. Effects, etc.] As described above, the sound measuring instrument 100b according to the embodiment comprises a light source 111 (see Figure 4) that emits laser light, a frame portion 120b that surrounds a predetermined space through which sound passes so as to intersect with the direction of sound propagation and has at least one reflective surface 3211a, 3211b, 3211c, 3211d directed toward the predetermined space, and a light receiving portion 115 (see Figure 4) that receives the laser light obtained by multiple reflection by the at least one reflective surface 3211a, 3211b, 3211c, 3211d, wherein the at least one reflective surface 3211a, 3211b, 3211c, 3211d is arranged to cause multiple reflections of the laser light in the predetermined space when the predetermined space is viewed from the direction of sound propagation.

[0134] As a result, the sound measuring instrument 100b can extend the optical path length of the laser beam within a predetermined space, thereby improving its sound pressure sensitivity.

[0135] For example, in the sound measuring instrument 100b according to the embodiment, at least one reflective surface 3211a, 3211b, 3211c, 3211d may be formed of at least one concave surface or a flat surface.

[0136] This makes it easier for the sound measuring instrument 100b to adjust the optical path length of the laser beam within a predetermined space to a desired length. Furthermore, for example, the sound measuring instrument 100b can also adjust the size of the predetermined space and the optical path length of the laser beam according to the location where the sound measuring instrument 100b is installed, the size of the installation location, or the characteristics of the sound being measured (e.g., frequency or sound pressure).

[0137] For example, in the sound measuring instrument 100b according to the embodiment, at least one reflective surface 3211a, 3211b, 3211c, 3211d may be formed in a series.

[0138] As a result, the sound measuring instrument 100b can have a series of smooth reflective surfaces, allowing for a larger area to reflect the laser light. Therefore, with the sound measuring instrument 100b, the user can more easily design the optical path of the laser light and reduce losses caused by the laser light escaping from the reflective surface.

[0139] For example, in the sound measuring instrument 100b according to the embodiment, at least one reflective surface 3211a, 3211b, 3211c, 3211d is a plurality of reflective surfaces, and the orientation of each of the plurality of reflective surfaces 3211a, 3211b, 3211c, 3211d may be different within a predetermined space.

[0140] As a result, the sound measuring instrument 100b can reflect laser light in multiple different directions within a predetermined space, thereby easily extending the optical path length within that space.

[0141] For example, in the sound measuring instrument 100b according to the embodiment, the shape of the frame portion 120b may be a polygon having three or more sides when viewed from the direction of sound propagation.

[0142] As a result, the sound measuring instrument 100b can appropriately set the size and shape of a predetermined space, or the optical path length of the laser beam, etc., according to, for example, the location where the sound measuring instrument 100b is installed, the size of the installation location, or the characteristics of the sound being measured, thereby enabling more accurate sound measurement.

[0143] For example, in the sound measuring instrument 100b according to the embodiment, the frame portion 120b is composed of at least one reflective member 321a, 321b, 321c, 321d, and the at least one reflective member 321a, 321b, 321c, 321d is a plurality of reflective members, and the plurality of reflective members 321a, 321b, 321c, 321d may be spaced apart from each other.

[0144] This allows the sound measuring instrument 100b to easily adjust the installation angles of the multiple reflective members 321a, 321b, 321c, and 321d. Therefore, the sound measuring instrument 100b can easily adjust the optical path length of the laser beam within a predetermined space.

[0145] For example, the sound measuring instrument 100b according to the embodiment may further include at least one angle-adjusting reflective member 322 that reflects laser light and allows adjustment of the reflection angle of the laser light.

[0146] This allows the sound measuring instrument 100b to adjust the reflection angle of the laser beam and adjust the optical path of the laser beam.

[0147] For example, in the sound measuring instrument 100b according to the embodiment, at least one angle-adjusting reflective member 322 may be arranged independently of the frame portion 120b.

[0148] This allows the sound measuring instrument 100b to finely adjust the angle of the laser beam and precisely adjust the optical path of the laser beam.

[0149] For example, in a sound measuring instrument 100b according to one aspect of the present disclosure, at least one angle-adjusting reflective member 322 may be fixedly positioned on the frame portion 120b.

[0150] This allows the sound measuring instrument 100b to stabilize the angle of the laser beam without fluctuation. Furthermore, the configuration is simplified.

[0151] (Variation 3) [1. Structure] Next, the configuration of the sound measuring instrument according to Modification 3 will be described. Figure 11 is a diagram showing an example of the configuration of the sound measuring instrument 100c according to Modification 3.

[0152] The sound measuring instrument 100b according to Modification 2 comprises four reflective members 321a, 321b, 321c, and 321d having planar reflective surfaces, and shows an example in which the reflective members 321a, 321b, 321c, and 321d are arranged to surround a predetermined space in a triangle when viewed from the direction of sound propagation. The sound measuring instrument 100c according to Modification 3 comprises one reflective member 421 having an uneven reflective surface in which a plurality of planar reflective surfaces are formed in a series, and the shape of the frame portion 120c when viewed from the direction of sound propagation Six This differs from the embodiment, modification 1, and modification 2 in that it has an angular shape. The differences from the embodiment, modification 1, and modification 2 will be explained below.

[0153] The reflective member 421 has multiple reflective surfaces 4211. These reflective surfaces are planar and formed in a continuous sequence. Furthermore, the frame portion 120c includes one angle-adjusting reflective member 422. The angle-adjusting reflective member 422 adjusts the reflection angle of the laser beam on the reflective surface 4221 by adjusting the orientation of the reflective surface 4221. In other words, the angle-adjusting reflective member 422 is used to return the laser beam to the measuring unit 110.

[0154] The sound measuring instrument 100c according to Modification 3, having the above configuration, allows for the measurement within a predetermined space. various Because the laser beam can be reflected multiple times in any direction, the optical path length can be extended without changing the size of the sound receiving unit.

[0155] The angle-adjusting reflective member 422 does not necessarily have to be positioned independently of the reflective member 421. For example, the angle-adjusting reflective member 422 may be fixed to the reflective member 421.

[0156] [2. Effects, etc.] As described above, the sound measuring instrument 100c according to the embodiment comprises a light source 111 (see Figure 4) that emits laser light, a frame portion 120c that surrounds a predetermined space through which sound passes so as to intersect with the direction of sound propagation and has at least one reflective surface 4211 directed toward the predetermined space, and a light receiving portion 115 (see Figure 4) that receives the laser light obtained by multiple reflection by the at least one reflective surface 4211, wherein the at least one reflective surface 4211 is arranged so as to cause multiple reflections of the laser light in the predetermined space when the predetermined space is viewed from the direction of sound propagation.

[0157] As a result, the sound measuring instrument 100c can extend the optical path length of the laser beam within a predetermined space, thereby improving its sound pressure sensitivity.

[0158] For example, in the sound measuring instrument 100c according to the embodiment, at least one reflective surface 4211 may be formed of at least one concave surface or a flat surface.

[0159] This makes it easier for the sound measuring instrument 100c to adjust the optical path length of the laser beam within a predetermined space to a desired length. Furthermore, for example, the sound measuring instrument 100c can also adjust the size of the predetermined space and the optical path length of the laser beam according to the location where the sound measuring instrument 100c is installed, the size of the installation location, or the characteristics of the sound being measured (e.g., frequency or sound pressure).

[0160] For example, in the sound measuring instrument 100c according to the embodiment, at least one reflective surface 4211 may be formed in a continuous sequence.

[0161] As a result, the sound measuring instrument 100c can have a series of smooth reflective surfaces, allowing for a larger area to reflect the laser light. Therefore, with the sound measuring instrument 100c, the user can more easily design the optical path of the laser light and reduce losses caused by the laser light escaping from the reflective surface.

[0162] For example, in the sound measuring instrument 100c according to the embodiment, at least one reflective surface 4211 is a plurality of reflective surfaces, and the orientation of each of the plurality of reflective surfaces 4211 may be different within a predetermined space.

[0163] As a result, the sound measuring instrument 100c can reflect laser light in multiple different directions within a predetermined space, thereby easily extending the optical path length within that space.

[0164] For example, in the sound measuring instrument 100c according to the embodiment, the shape of the frame portion 120c may be a polygon having three or more sides when viewed from the direction of sound propagation.

[0165] As a result, the sound measuring instrument 100c can appropriately set the size and shape of a predetermined space, or the optical path length of the laser beam, etc., according to, for example, the location where the sound measuring instrument 100c is installed, the size of the installation location, or the characteristics of the sound being measured, thereby enabling more accurate sound measurement.

[0166] For example, in the sound measuring instrument 100c according to the embodiment, the frame portion 120c is composed of at least one reflective member 421, and the at least one reflective member 421 may be just one reflective member.

[0167] This allows the sound measuring instrument 100c to measure sound more easily. For example, the sound measuring instrument 100c only requires the installation of a frame 120c consisting of one reflective member 421, eliminating the need for the trouble of adjusting the relative positions of reflective members, as is the case with frame structures consisting of two or more reflective members.

[0168] For example, the sound measuring instrument 100c according to the embodiment may further include at least one angle-adjusting reflective member 422 that reflects laser light and allows adjustment of the reflection angle of the laser light.

[0169] This allows the sound measuring instrument 100c to adjust the reflection angle of the laser beam and adjust the optical path of the laser beam.

[0170] For example, in the sound measuring instrument 100c according to the embodiment, at least one angle-adjusting reflective member 422 may be arranged independently of the frame portion 120c.

[0171] This allows the sound measuring instrument 100c to finely adjust the angle of the laser beam and precisely adjust the optical path of the laser beam.

[0172] For example, in a sound measuring instrument 100c according to one aspect of the present disclosure, at least one angle-adjusting reflective member 422 may be fixedly positioned on the frame portion 120c.

[0173] This allows the sound measuring instrument 100c to stabilize the angle of the laser beam without fluctuation. Furthermore, the configuration is simplified.

[0174] (Modification 4) [1. Structure] Next, the configuration of the sound measuring instrument according to Modification 4 will be described. Figure 12 is a diagram showing an example of the configuration of the sound measuring instrument 100d according to Modification 4. Figure 12(a) is a perspective view of the sound measuring instrument 100d viewed from diagonally above, and Figure 12(b) is a cross-sectional view obtained by cutting the frame portion 120d of the sound measuring instrument 100d shown in Figure 12(a) with respect to the ZX plane.

[0175] In the above embodiments and modifications 1 to 3, each of the frame portions 120 to 120c had at least one planar reflective surface, but modification 4 differs from the embodiments and modifications 1 to 3 in that it has a concave reflective surface.

[0176] Here, a concave surface includes a surface that curves downward and is recessed; for example, a bowl-shaped recessed surface is also called a concave surface.

[0177] The two reflective members 521a and 521b each have one reflective surface 5211a and 5211b. Each of these reflective surfaces is a concave surface and is directed toward a predetermined space. Furthermore, the frame portion 120d includes one angle-adjusting reflective member 522. The angle-adjusting reflective member 522 adjusts the reflection angle of the laser beam on the reflective surface 5221 by adjusting the orientation of the reflective surface 5221. In other words, the angle-adjusting reflective member 522 is used to return the laser beam to the measuring unit 110.

[0178] The sound measuring instrument 100d according to Modification 4, having the above configuration, can not only cause multiple reflections of laser light between a single reflective member 521a, 521b on the ZX plane within a predetermined space, but also cause multiple reflections in the direction of sound propagation (in this case, the Y axis direction). Therefore, the optical path length can also be extended in the depth direction within the predetermined space.

[0179] [2. Effects, etc.] As described above, the sound measuring instrument 100d according to the embodiment comprises a light source 111 (see Figure 4) that emits laser light, a frame portion 120d that surrounds a predetermined space through which sound passes so as to intersect with the direction of sound propagation and has at least one reflective surface 5211a, 5211b directed toward the predetermined space, and a light receiving portion 115 (see Figure 4) that receives the laser light obtained by multiple reflection by the at least one reflective surface 5211a, 5211b, wherein the at least one reflective surface 5211a, 5211b is arranged so as to cause multiple reflections of the laser light in the predetermined space when the predetermined space is viewed from the direction of sound propagation.

[0180] As a result, the sound measuring instrument 100d can extend the optical path length of the laser beam within a predetermined space, thereby improving its sound pressure sensitivity.

[0181] For example, in the sound measuring instrument 100d according to the embodiment, at least one reflective surface 5211a, 5211b may be formed of at least one concave surface or a flat surface.

[0182] This makes it easier for the sound measuring instrument 100d to adjust the optical path length of the laser beam within a predetermined space to a desired length. Furthermore, for example, the sound measuring instrument 100d can also adjust the size of the predetermined space and the optical path length of the laser beam according to the location where the sound measuring instrument 100d is installed, the size of the installation location, or the characteristics of the sound being measured (e.g., frequency or sound pressure).

[0183] For example, in the sound measuring instrument 100d according to the embodiment, at least one reflective surface 5211a, 5211b may be formed in a continuous sequence.

[0184] As a result, the sound measuring instrument 100d can have a series of smooth reflective surfaces, allowing for a larger area to reflect the laser light. Therefore, with the sound measuring instrument 100d, the user can more easily design the optical path of the laser light and reduce losses caused by the laser light escaping from the reflective surface.

[0185] For example, in the sound measuring instrument 100d according to the embodiment, the frame portion 120d is composed of at least one reflective member 521a, 521b, and the at least one reflective member 521a, 521b is a plurality of reflective members, and the plurality of reflective members 521a, 521b may be spaced apart from each other.

[0186] This allows the sound measuring instrument 100d to easily adjust the installation angles of the multiple reflective members 521a and 521b. Therefore, the sound measuring instrument 100d can easily adjust the optical path length of the laser beam within a predetermined space.

[0187] For example, the sound measuring instrument 100d according to the embodiment may further include at least one angle-adjusting reflective member 522 that reflects laser light and allows adjustment of the reflection angle of the laser light.

[0188] This allows the sound measuring instrument 100d to adjust the reflection angle of the laser beam and adjust the optical path of the laser beam.

[0189] For example, in the sound measuring instrument 100d according to the embodiment, at least one angle-adjusting reflective member 522 may be arranged independently of the frame portion 120d.

[0190] This allows the sound measuring instrument 100d to finely adjust the angle of the laser beam and precisely adjust the optical path of the laser beam.

[0191] For example, in a sound measuring instrument 100d according to one aspect of the present disclosure, at least one angle-adjusting reflective member 522 may be fixedly positioned on the frame portion 120d.

[0192] This allows the sound measuring instrument 100d to stabilize the angle of the laser beam without fluctuation. Furthermore, the configuration is simplified.

[0193] (Variation 5) [1. Structure] Next, the configuration of the sound measuring instrument according to Modification 5 will be described. Figure 13 shows an example of the configuration of the sound measuring instrument 100e according to Modification 5.

[0194] In the above embodiments and modifications 1 to 4, the laser light incident from the measurement unit 110 into a predetermined space was returned to the measurement unit 110. However, modification 5 differs from the embodiments and modifications 1 to 4 in that the laser light is not returned to the measurement unit 110, but is instead irradiated onto the photodetection unit 160.

[0195] The sound measuring instrument 100e according to Modification 5 comprises a light source 111, a frame portion 120d, a focusing lens 150, and a light detection unit 160. The light detection unit 160 is, for example, a photodiode. In Modification 5, the frame portion 120d differs from the frame portion 120a in the embodiment in that it does not have an angle adjustment reflective member 122.

[0196] The sound measuring instrument 100e according to Modification 5 has the above configuration, which allows for an extended optical path length, thereby improving sound pressure sensitivity. Furthermore, since the sound measuring instrument 100e does not require the laser beam to be returned to the measuring unit, as in the embodiment and the sound measuring instruments according to Modifications 1 to 4, sound can be measured more easily.

[0197] (Other embodiments) The above description has provided an overview of sound measuring instruments according to one or more embodiments of the present disclosure, based on the above embodiments and modifications. However, the present disclosure is not limited to these embodiments and modifications. Without departing from the spirit of the present disclosure, various modifications that a person skilled in the art could conceive of may be applied to the embodiments, or configurations that combine components from different embodiments may also be included within the scope of one or more embodiments of the present disclosure.

[0198] For example, the directivity of the sound measuring instrument may be adjusted by changing the ratio of the horizontal width to the vertical width of the frame when the frame is viewed from the direction of sound propagation. This allows the sound measuring instrument to reduce noise, thereby improving the accuracy of sound measurement.

[0199] Furthermore, for example, the frame may be adjusted so that, when viewed from the direction of sound propagation, at least one of its horizontal or vertical widths is increased, thereby altering the horizontal and vertical directivity of the sound measuring instrument. This allows the sound measuring instrument to freely adjust its directivity to match the sound being measured, thereby improving the accuracy of sound measurement.

[0200] The relationship between the ratio of the horizontal width to the vertical width of the frame and the directivity of the sound measuring instrument will be explained in detail below, with reference to Figures 14 and 15.

[0201] [Example 1] The first example describes a case where the ratio of the horizontal width to the vertical width of the frame is 1:1. Figure 14 shows the first example of the relationship between the ratio of the horizontal width to the vertical width of the frame when viewed from the direction of sound propagation and the directivity of the sound measuring instrument. In Figure 14, the sound measuring instrument 100 shown in Figure 2 is used, but for the sake of clarity, the frame 120 is not shown.

[0202] Figure 14(a) shows the sound receiving section when the frame 120 is viewed from the direction of sound propagation. The sound receiving section receives sound passing through a predetermined space enclosed by the frame 120 by the multiple reflection of the laser light within that predetermined space. The sound receiving section can be considered, for example, as a microphone array in which many microphones are arranged on the optical path of the multiple reflected laser light. Specifically, in Figure 14(a), the optical path of the laser light that undergoes multiple reflections within the predetermined space is shown by a solid line when the frame 120 is viewed from the direction of sound propagation.

[0203] In the first example, the frame 120 is installed at a distance of 1 meter from the sound source. When the frame 120 is viewed from the direction of sound propagation, the center of the sound-receiving part (more specifically, the sound-source-facing side of the sound-receiving part, in other words, the sound-receiving surface) and the sound source are aligned in a straight line. Hereafter, the straight line passing through the center of the sound-receiving part and the sound source will be referred to as the principal axis.

[0204] figure 14 Figure (b) is a graph showing the directivity of the sound measuring instrument when the frequency of the sound being measured is 1 kHz. 14 Figure (c) is a graph showing the directivity of the sound measuring instrument when the frequency of the sound being measured is 10 kHz. 14 (b) and Figure 14 In (c), the horizontal axis represents the angle (degrees), and the vertical axis represents the difference (in other words, the relative level) between the sound pressure of the sound measured on the principal axis (angle = 0°) at the sound receiving unit and the sound measured at each angle.

[0205] Figure 14(b) and Figure 14 As shown in (c), it was confirmed that a symmetrical directivity is formed around the main axis in the sound receiving section.

[0206] [Second example] The second example describes a case where the ratio of the horizontal width to the vertical width of the frame is 2:1. Figure 15 shows the second example of the relationship between the ratio of the horizontal width to the vertical width of the frame when viewed from the direction of sound propagation and the directivity of the sound measuring instrument. In Figure 15 as well, the illustration of the frame is omitted for the sake of clarity.

[0207] Figure 15(a) shows the sound receiving section when the frame is viewed from the direction of sound propagation. The sound receiving section has been described above, so it will not be described here. In Figure 15(a), the optical path of the laser beam that undergoes multiple reflections within a predetermined space is shown by solid lines when the frame is viewed from the direction of sound propagation.

[0208] In the second example as well, the frame is installed at a distance of 1 meter from the sound source.

[0209] figure 15 Figure (b) is a graph showing the directivity of the sound measuring instrument when the frequency of the sound being measured is 1 kHz. 15 Figure (c) is a graph showing the directivity of the sound measuring instrument when the frequency of the sound being measured is 10 kHz. 15 (b) and Figure 15 In (c), the horizontal axis represents the angle (degrees), and the vertical axis represents the difference (in other words, the relative level) between the sound pressure of the sound measured on the principal axis (angle = 0°) at the sound receiving unit and the sound measured at each angle.

[0210] Figure 15(b) and Figure 15 As shown in (c), it was confirmed that a symmetrical directivity is formed around the main axis in the sound receiving section. Furthermore, it was confirmed that when the horizontal width of the sound receiving section is made larger than the vertical width, the directivity of the sound measured horizontally becomes higher than that of the sound measured vertically in the sound receiving section.

[0211] As described above, the embodiments described in the first and second examples may also be included in sound measuring instruments relating to one or more embodiments of the present disclosure.

[0212] Furthermore, one aspect of this disclosure may be a sound measurement method in which characteristic components included in the device are used as steps, rather than just a sound measuring instrument. Another aspect of this disclosure may be a computer program that causes a computer to execute each characteristic step included in the sound measurement method. Another aspect of this disclosure may be a computer-readable non-temporary recording medium on which such a computer program is recorded. [Industrial applicability]

[0213] According to this disclosure, since it does not utilize the mechanical vibration of a diaphragm, it is possible to measure sound across a wider wavelength range, particularly in the ultrasonic range. Therefore, by measuring sound in the ultrasonic range, it can be used for the early detection or prediction of malfunctions in equipment, as well as for estimating human behavior. [Explanation of Symbols]

[0214] 1. Optical microphone 10. Laser Doppler Vibrometer 21a, 21b reflector 121a, 121b, 221a, 221b, 221c, 221d, 321a, 321b, 321c, 321d, 421, 521a, 521b Reflective material 20, 120, 120a, 120b, 120c, 120d Frame body 211a, 211b, 221, 1211a, 1211b, 1221, 2211a, 2211b, 2211c, 2211d, 2221a, 2221b, 3211a, 3211b, 3211c, 3211d, 3221,4211, 4221, 5211a, 5211b, 5221 reflective surface 22 Reflector for angle adjustment 122, 222a, 222b, 322, 422, 522 Angle adjustment reflective members 30, 130 calculation section 100, 100a, 100b, 100c, 100d, 100e Sound Measuring Instruments 110 Measurement Unit 111 Light source 112a First Beam Splitter 112b Second Beam Splitter 112c Third Beam Splitter 113 Miller 114a AOM driver 114b AOM 115 Light receiving part 116 Detection circuit 140 Collimating Lens 150 Focusing Lens 160 Light detection unit

Claims

1. A sound measuring instrument, A light source that emits laser light, A frame portion that surrounds a predetermined space through which sound passes so as to intersect with the direction of sound propagation, and has at least one reflective surface directed toward the predetermined space, A light receiving unit that receives the laser light obtained by multiple reflection by at least one of the reflective surfaces, Equipped with, The at least one reflective surface is arranged such that, when the predetermined space is viewed from the direction of sound propagation, the laser light intersects and undergoes multiple reflections within the predetermined space. The frame portion is configured such that, when viewed from the direction of sound propagation, the ratio between the horizontal width of the frame portion and the vertical width of the frame portion is changed, thereby adjusting the directivity of the sound measuring instrument. Sound measuring instrument.

2. A sound measuring instrument, A light source that emits laser light, A frame portion that surrounds a predetermined space through which sound passes so as to intersect with the direction of sound propagation, and has at least one reflective surface directed toward the predetermined space, A light receiving unit that receives the laser light obtained by multiple reflection by at least one of the reflective surfaces, Equipped with, The at least one reflective surface is arranged such that, when the predetermined space is viewed from the direction of sound propagation, the laser light intersects and undergoes multiple reflections within the predetermined space. The frame portion is adjusted so that the horizontal and vertical directivity of the sound measuring instrument differs when viewed from the direction of sound propagation, by increasing at least one of the horizontal width and vertical width of the frame portion. Sound measuring instrument.

3. The at least one reflective surface is formed by at least one concave or flat surface. The sound measuring instrument according to claim 1 or 2.

4. The at least one reflective surface is formed in a series, The sound measuring device according to claim 3.

5. The at least one reflective surface is a plurality of reflective surfaces, and the orientation of each of the plurality of reflective surfaces is different within the predetermined space. A sound measuring instrument according to any one of claims 1 to 4.

6. The shape of the frame portion is a polygon with three or more sides when viewed from the direction of sound propagation. A sound measuring instrument according to any one of claims 1 to 5.

7. The shape of the polygon is triangular, quadrilateral, pentagonal, or hexagonal. The sound measuring device according to claim 6.

8. The frame portion is composed of at least one reflective member, The aforementioned at least one reflective member is a plurality of reflective members, The aforementioned plurality of reflective members are each arranged at a distance from each other. A sound measuring instrument according to any one of claims 1 to 7.

9. The frame portion is composed of at least one reflective member, The aforementioned at least one reflective member is one reflective member, A sound measuring instrument according to any one of claims 1 to 7.

10. The aforementioned sound measuring instrument further includes a collimating lens, The light source causes the laser light to be incident on the predetermined space through the collimating lens. A sound measuring instrument according to any one of claims 1 to 9.

11. The sound measuring instrument further includes at least one angle-adjusting reflective member that reflects the laser light and allows adjustment of the reflection angle of the laser light. A sound measuring instrument according to any one of claims 1 to 10.

12. The at least one angle-adjusting reflective member is arranged independently of the frame portion. The sound measuring device according to claim 11.

13. The at least one angle-adjusting reflective member is fixedly positioned on the frame. The sound measuring device according to claim 11.

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