JP7535482B2 - Body sound detector - Google Patents

Description

The disclosure in this specification relates to a biological sound detection device.

Patent document 1 discloses a microphone for collecting biological sounds. The contents of the prior art document are incorporated by reference as explanations of the technical elements in this specification.

JP 2013-74916 A

In the body sound collecting microphone described in Patent Document 1, that is, the body sound detection device, the second body sound propagation section is filled in the storage space provided by the housing and the first body sound propagation section. Therefore, of the housing and the first body sound propagation section that provide the storage space, the body sound is transmitted to the second body sound propagation section via the first body sound propagation section. However, the body sound cannot be separated. For example, the sound (acoustic signal) of each organ cannot be separated and detected. In the above-mentioned viewpoints, or in other viewpoints not mentioned, further improvements are required for the body sound detection device.

One disclosed objective is to provide a body sound detection device that can separate and detect body sounds.

The body sound detection device disclosed herein is
A housing (20);
A detection unit (30) that provides a storage space together with the housing and detects an acoustic signal that is a body sound;
A medium (40) disposed in the accommodation space and having an acoustic impedance closer to that of water than to that of air;
A plurality of elements (50, 50A, 50B, 50C) are disposed in the accommodation space and convert an acoustic signal transmitted through a detection unit and a medium into an electric signal;
Each of the elements has a surface film (52, 52A, 52B, 52C) that has a larger acoustic impedance than the medium and forms a surface facing the detection unit,
The multiple elements have different angles of total reflection of an acoustic signal based on a normal line perpendicular to the arrangement direction of the multiple elements.

According to the disclosed biological sound detection device, each of the multiple elements has a surface film. The surface film has a higher acoustic impedance than the medium and has a total reflection angle for the acoustic signal. The multiple elements have different total reflection angles of the acoustic signal based on a normal line perpendicular to the arrangement direction. This makes it possible to narrow the directivity compared to a configuration in which the total reflection angles are equal. As a result, it is possible to provide a biological sound detection device that can separate and detect biological sounds.

The various aspects disclosed in this specification employ different technical means to achieve their respective objectives. The claims and the reference characters in parentheses in this section are illustrative of the corresponding relationships with the embodiments described below, and are not intended to limit the technical scope. The objectives, features, and advantages disclosed in this specification will become clearer with reference to the detailed description that follows and the accompanying drawings.

FIG. 1 is a diagram showing an arrangement of a body sound detection device according to a first embodiment. FIG. 1 is a diagram illustrating a body sound detection device. FIG. 2 is a diagram showing a normal and an incident angle θ. FIG. 1 is a diagram showing the relationship between the incident angle θ and the energy propagation loss at the interface between water and nylon. FIG. 1 is a diagram showing the relationship between the incident angle θ and the energy propagation loss at the interface between water and polyethylene. FIG. 13 is a diagram showing the difference region of the attenuation characteristics of two elements. FIG. FIG. 11 is a partial cross-sectional view showing the periphery of an element in a body sound detection device according to a second embodiment. FIG. 13 is a diagram showing the difference domain of the attenuation characteristics of three elements. FIG. 13 is a perspective view showing a surface membrane in a body sound detecting device according to a third embodiment. FIG. FIG. FIG. 13 is a perspective view showing a modified example of the surface film. FIG. FIG. FIG. 13 is a perspective view showing a surface membrane in a body sound detecting device according to a fourth embodiment. FIG. FIG. 13 is a plan view showing a modified example of the surface film. FIG. FIG. 13 is a partial cross-sectional view showing the periphery of an element in a body sound detection device according to a fifth embodiment. 13A and 13B are diagrams showing other modified examples. 13A and 13B are diagrams showing other modified examples. 13A and 13B are diagrams showing other modified examples.

Below, several embodiments will be described with reference to the drawings. Note that in each embodiment, corresponding components are given the same reference numerals, and duplicated descriptions may be omitted. When only a portion of the configuration is described in each embodiment, the configuration of the other embodiment described above can be applied to the other portions of the configuration. In addition to the combinations of configurations explicitly stated in the description of each embodiment, configurations of several embodiments can be partially combined together even if not explicitly stated, as long as there is no particular problem with the combination.

First Embodiment
First, the arrangement of the body sound detecting device according to this embodiment will be described with reference to FIG.

<Layout of Body Sound Detector>
As shown in Fig. 1, the body sound detection device 10 is disposed in a moving body, as an example. The moving body may be a vehicle, an aircraft, a ship, a construction machine, or the like. The moving body includes a seat 100 on which an occupant 110 sits. The seat 100 includes a seating portion 101 and a backrest portion 102. The seating portion 101 supports the buttocks, thighs, and the like of the occupant 110. The backrest portion 102 supports the back of the occupant 110. The moving body includes a seat belt 103. The seat belt 103 restrains the occupant 110 to the seat 100.

The body sound detection device 10 of this embodiment is disposed in at least one of the seating portion 101, the backrest portion 102, and the seat belt 103 of the seat 100. FIG. 1 shows an example in which the body sound detection device 10 is disposed in the backrest portion 102. The body sound detection device 10 detects the body sound of an occupant 110. The occupant 110 corresponds to a living body. The body sound is an acoustic signal generated from each part of the living body. The body sound is a general body sound such as heart sounds, sounds of organs other than the heart (e.g., lung sounds), breathing sounds, and blood flow sounds (e.g., ballistocardial sounds, which are blood flow in the arteries). The body sound detection device 10 detects the body sound via the members that constitute the seat 100.

<Body sound detector>
Next, the body sound detecting device will be described with reference to Fig. 2. Fig. 2 is a partial cross-sectional view showing the body sound detecting device.

As shown in FIG. 2, the body sound detection device 10 includes a body sound detection sensor 11 and a signal processing unit 12. The body sound detection sensor 11 includes a housing 20, a detection unit 30, a medium 40, and a plurality of elements 50.

The housing 20 provides a storage space for storing the detection unit 30 as well as other elements of the body sound detection sensor 11. There are no particular limitations on the material that the housing 20 is made of. The housing 20 is formed from materials such as metal, ceramic, glass, and resin. In this embodiment, the housing 20 has a case 21 and a cover 22. The case 21 is box-shaped with one side open. The cover 22 is provided so as to cover part of the opening of the case 21. The cover 22 is sometimes referred to as a lid.

The detection unit 30 provides an accommodation space together with the housing 20. The detection unit 30 is provided in the housing 20. The detection unit 30 is fixed to the housing 20. In this embodiment, the detection unit 30 is provided in the cover 22. The detection unit 30 is provided so as to close the opening of the cover 22. The detection unit 30, together with the cover 22, closes the opening of the case 21. The inner surface of the detection unit 30 and the inner surface of the housing 20 define (partition) the accommodation space.

The storage space is not limited to the above-mentioned configuration. For example, the housing 20 may have only the case 21, and the detection unit 30 may close the opening of the case 21. In other words, the cover 22 may be eliminated. The fixing structure between the housing 20 and the detection unit 30 is not particularly limited. In order to hold the medium 40, sealing or the like may be applied as necessary. The fixing structure between the case 21 and the cover 22 is also not particularly limited. Sealing or the like may be applied as necessary.

The detection unit 30 is formed using a solid material that has an acoustic impedance closer to that of water than the material that constitutes the housing 20. The detection unit 30 is preferably made of a material that has an acoustic impedance that is approximately equal to that of water. Specifically, it is preferable to use a material whose acoustic impedance ratio to water is within the range of 0.5 to 5. More preferably, it is preferable to use a material whose acoustic impedance ratio to water is within the range of 0.8 to 2. This makes it possible to reduce reflection loss at the interface of the detection unit 30.

The detection unit 30 of this embodiment is formed using silicone rubber. The acoustic impedance of silicone rubber is 1.44×10 ⁶ kg/(s·m ² ). The acoustic impedance of water is 1.53×10 ⁶ kg/(s·m ² ). The acoustic impedance of the human body is almost equal to that of water. The acoustic impedance of the human body is 1.99×10 ⁶ kg/(s·m ² ).

If the housing 20 is made of metal, for example, its acoustic impedance is 10 times or more that of water. As a result, the body sound is detected by the detection unit 30 and reflected by the housing 20. The body sound is transmitted to the medium 40 of the storage space through the detection unit 30. In this way, the detection unit 30 detects the body sound and transmits it to the medium 40. The detection unit 30 is a part of the wall member that provides the storage space that transmits the body sound locally.

The medium 40 is disposed in the accommodation space. The medium 40 is in contact with the inner surface of the housing 20 and the inner surface of the detection unit 30. The medium 40 is disposed in the propagation path between the detection unit 30 and the element 50. The medium 40 transmits the body sound input via the detection unit 30 to the element 50. In this embodiment, the medium 40 fills almost the entire accommodation space.

The medium 40 has an acoustic impedance closer to that of water than that of air. The medium 40 has an acoustic impedance greater than that of air and less than that of the material constituting the housing 20. The medium 40 should have an acoustic impedance that is approximately equal to that of water. Specifically, it is preferable to use a material whose acoustic impedance ratio to water is within the range of 0.5 to 2. More preferably, it is preferable to use a material whose acoustic impedance ratio to water is within the range of 0.8 to 1.25. This makes it possible to reduce reflection loss at the interface between the detection unit 30 and the medium 40, that is, reflection loss in the propagation path of the body sound (acoustic signal) from the detection unit 30 to the element 50.

As the medium 40, for example, a liquid material such as water or silicone oil, ultrasonic gel, etc. can be used. The acoustic impedance of silicone oil is 1.41×10 ⁶ kg/(s·m ² ). The acoustic impedance of ultrasonic gel is 1.41×10 ⁶ kg/(s·m ² ). The acoustic impedance of water is as described above. In this embodiment, water is used as the medium 40. The acoustic impedance of air is 4.39×10 ² kg/(s·m ² ).

The multiple elements 50 convert the body sound into an electrical signal. Each element 50 converts the body sound transmitted through the detection unit 30 and the medium 40 into an electrical signal. The white arrows in FIG. 2 indicate the body sound (acoustic signal). Each element 50 is covered by the medium 40. Each element 50 independently outputs an electrical signal. Details of the elements 50 will be described later.

The signal processing unit 12 performs a predetermined process on the output signals (electrical signals) of the multiple elements 50. The signal processing unit 12 performs differential processing as a process for separating body sounds. The signal processing unit 12 performs differential processing using the output signals of two elements 50. The signal processing unit 12 may perform correction processing such as amplification on at least one of the output signals, and perform differential processing using the corrected output signal.

<Element>
Next, the element 50 will be described with reference to FIG.

As shown in FIG. 2, the element 50 has an element body 51 and a surface film 52. The element body 51 is formed with an element (converter) that converts body sounds into electrical signals. The element body 51 is fixed to the housing 20. As an example, the element body 51 in this embodiment is fixed to the bottom wall 211 of the case 21.

The conversion type of the converter is not particularly limited. For example, it may be a resistance change type or a capacitance change type. It may also be a piezoelectric type that generates an electromotive force. The element body 51 is formed, for example, using MEMS technology. MEMS is an abbreviation for Micro Electro Mechanical Systems. By using MEMS technology, the size of the element 50, and therefore the body sound detection device 10, can be reduced in size.

The surface film 52 is provided on one surface of the element body 51. The surface film 52 forms an opposing surface of the element 50 that faces the detection unit 30. The surface film 52 also functions to protect the element body 51. The surface film 52 is formed using a material that has a higher acoustic impedance than the medium 40. The surface film 52 has a total reflection angle at the interface with the medium 40. The body sound (acoustic signal) is totally reflected at an angle of incidence greater than a predetermined angle, and is not transmitted to the element 50 (element body 51). The predetermined angle is sometimes referred to as a critical angle.

The body sound detection device 10 of this embodiment includes two elements 50. One of the elements 50, element 50A, has an element body 51A and a surface film 52A. The other of the elements 50, element 50B, has an element body 51B and a surface film 52B. The multiple elements 50 include element 50A (first element) and element 50B (second element).

The two elements 50A and 50B are arranged so that the angles of incidence θ with respect to normals NA and NB, which will be described later, are approximately equal to each other with respect to an acoustic signal (body sound) from a predetermined direction. In other words, the normals NA and NB are arranged so that they are approximately parallel. The two elements 50A and 50B are arranged side by side in the X direction. In the Y direction perpendicular to the X direction, the two elements 50A and 50B face the detection unit 30. In a plan view from the Y direction, the two elements 50A and 50B are arranged so as to be contained in the detection unit 30. In the Y direction, the elements 50A and 50B are arranged side by side with the detection unit 30. The element bodies 51A and 51B have, for example, a common structure. The Z direction shown in FIG. 2 is a direction perpendicular to both the X direction and the Y direction.

<Surface film>
Next, the surface film 52 will be described with reference to FIGS.

In this embodiment, the acoustic impedances of the surface films 52A and 52B are different from each other. The acoustic impedance is a value specific to the material. As an example, the material of the surface film 52A is nylon, and the material of the surface film 52B is polyethylene. Except for the fact that the surface films 52A and 52B are made of different materials, they have a common structure.

The surface films 52A and 52B are, for example, substantially rectangular, for example substantially square, in plan view in the Y direction. The surface films 52A and 52B are, for example, flat films with a substantially uniform thickness. The thickness direction of each of the surface films 52A and 52B is substantially parallel to the Y direction. The surface films 52A and 52B are substantially rectangular. The surface films 52A and 52B are composed of flat surfaces.

3 shows the relationship between the normal line common to the multiple elements 50 and the normal line of each element 50. As shown in FIG. 3, the normal line NL common to the multiple elements 50 is perpendicular to the X direction, which is the arrangement direction of the multiple elements 50. The normal line NL is approximately parallel to the Y direction, which is the arrangement direction (opposing direction) of the elements 50 and the detection unit 30. The normal line NA of element 50A is perpendicular to the surface of element 50A facing the detection unit 30. The normal line NA in this embodiment is approximately parallel to the Y direction. The normal line NB of element 50B is perpendicular to the surface of element 50B facing the detection unit 30. The normal line NB in this embodiment is approximately parallel to the Y direction. That is, in this embodiment, the normal lines NA and NB are parallel to the normal line NL.

Figure 4 shows the relationship between the angle of incidence θ (deg) of the acoustic signal, which is a biological sound, and the energy propagation loss (dB) at the interface between the surface film 52A, i.e., the element 50A, and the medium 40. Figure 4 shows the energy attenuation characteristics of the element 50A. In the element 50A, the angle of incidence θ is the angle of incidence with respect to the normal NA.

The acoustic impedance of the water constituting the medium 40 is as described above. The acoustic impedance of the nylon constituting the surface film 52A is 2.91×10 ⁶ kg/(s·m ² ). The total reflection angle described above is the incident angle θ at which the energy propagation loss exceeds a predetermined threshold. When the incident angle θ is 0 to 90 degrees, the total reflection angle is, for example, about 36 degrees to 90 degrees. In this embodiment, the normal NA is parallel to the normal NL. Therefore, the total reflection angle based on the normal NL is also 36 to 90 degrees, like the normal NA.

Figure 5 shows the relationship between the incident angle θ (deg) and the energy propagation loss (dB) at the interface between the surface film 52B, i.e., the element 50B and the medium 40. In other words, Figure 5 shows the energy attenuation characteristics of the element 50B. In the element 50B, the incident angle θ is the angle of incidence with respect to the normal NB.

The acoustic impedance of the water constituting the medium 40 is as described above. The acoustic impedance of the polyethylene constituting the surface film 52B is 1.75×10 ⁶ kg/(s·m ² ). When the incident angle θ is 0 to 90 degrees, the total reflection angle is, for example, about 52 degrees to 90 degrees. In this embodiment, the normal line NB is parallel to the normal line NL. Therefore, the total reflection angle based on the normal line NL is also 52 to 90 degrees, like the normal line NB. Therefore, the total reflection angle based on the normal line NL is different between the surface film 52A and the surface film 52B.

<Directivity>
Next, the directivity of the body sound detection device 10 will be described with reference to FIG. 6 and FIG.

When the element 50 has only the surface film 52A, as shown in FIG. 4, the incident angle θ has a directivity of 0 to 35 deg. When the element 50 has only the surface film 52B, as shown in FIG. 5, the incident angle θ has a directivity of 0 to 51 deg. When a single film is used in this way, it is difficult to narrow the directivity. In other words, it is difficult to separate and detect a specific body sound from multiple body sounds.

In contrast, the biological sound detection sensor 11 of this embodiment includes an element 50A having a surface film 52A, and an element 50B having a surface film 52B having a different acoustic impedance from that of the surface film 52A. By utilizing the fact that the total reflection angles of the acoustic signal (biological sound) based on the normal line NL are different from each other, the directivity can be narrowed.

Figure 6 shows the difference region between the attenuation characteristics of element 50A shown in Figure 4 and the attenuation characteristics of element 50B shown in Figure 5. In the difference region, a difference occurs in the energy attenuation of elements 50A and 50B. By using this difference region, a narrow directivity, specifically a directivity with an incident angle θ of 36 to 51 deg, can be achieved. Note that when the incident angle θ is 0 to 35 deg and 52 to 90 deg, there is no difference in the energy attenuation of elements 50A and 50B.

As described above, the signal processing unit 12 executes differential processing to separate the body sounds. Specifically, the output signal of element 50A is subtracted from the output signal of element 50B, which has a large total reflection angle. When the scales of the energy propagation loss are different as shown in Figures 4 and 5, the output signal may be corrected as necessary, for example by amplification processing. The differential signal obtained by differential processing includes body sounds from directions with an incidence angle θ of 36 to 51 deg. Body sounds from directions with an incidence angle θ of 0 to 35 deg and 52 to 90 deg are canceled by differential processing.

In other words, as shown in FIG. 7, the body sound detection device 10 equipped with multiple elements 50 has a directivity with an incident angle θ of 36 to 51 deg. Also, in the direction around the axis of the normal line NL, that is, in the φ direction, it has a directivity of 0 to 360 deg. FIG. 7 is a diagram showing the directivity of the body sound detection device 10. In FIG. 7, the φ direction is shown three-dimensionally to make the directivity easier to understand. The detection unit 30 has a size that takes into consideration the above-mentioned directivity in its positional relationship with the elements 50 so that the detection unit 30 detects body sounds and transmits them to the elements 50 via the medium 40.

Summary of the First Embodiment
According to the body sound detection device 10 of the present embodiment, a medium 40 having an acoustic impedance closer to that of water than that of air is disposed in the accommodation space. The body sound is transmitted from the detection unit 30 to the element 50 through the medium 40. This makes it possible to reduce reflection loss at the interface in the propagation path from the detection unit 30 to the element 50. The occupant 110 (living body), the clothes of the occupant 110, and the surface material of the seat 100 have acoustic impedance close to that of water. This makes it possible to reduce reflection loss in the propagation path from the living body to the element 50. As a result, it is possible to detect body sound even in a noisy environment of a moving body such as running noise, while suppressing a decrease in the intensity of the body sound (acoustic signal) detected by the element 50.

In this embodiment, the two elements 50 (50A, 50B) included in the body sound detection device 10 each have a surface film 52. The surface film 52 has a larger acoustic impedance than the medium 40 and has a total reflection angle for the acoustic signal (body sound). The two elements 50A, 50B have different total reflection angles of the acoustic signal based on the normal line NL. This makes it possible to narrow the directivity of the body sound detection device 10 compared to a configuration in which the total reflection angles are equal. Therefore, the body sound can be separated and detected.

The body sound detection device 10 (body sound detection sensor 11) of this embodiment is placed at a predetermined position and orientation with respect to the occupant 110 (living body) taking into consideration the above-mentioned directionality. This makes it possible to selectively detect a desired body sound in relation to the position of the occupant 110. For example, it is possible to selectively detect heart sounds.

In this embodiment, the acoustic impedances of the surface films 52A and 52B are made different, so that the angles of total reflection of the acoustic signal based on the normal line NL are made different between the two elements 50A and 50B. By simply adjusting the material (substance) that constitutes the surface film 52, it is possible to separate and detect body sounds with a simple structure.

The body sound detection device 10 may include a body sound detection sensor 11 and a signal processing unit 12, or may include only the body sound detection sensor 11. When the signal processing unit 12 is included as in this embodiment, differential processing of the output signals of elements 50A and 50B can be performed within the body sound detection device 10.

Second Embodiment
This embodiment is a modification based on the preceding embodiment, and the description of the preceding embodiment can be used. In the preceding embodiment, the body sound detection device 10 includes two elements 50 (50A, 50B). Instead of this, three or more elements 50 may be included.

Figure 8 is a partial cross-sectional view showing the periphery of the element in the body sound detection device 10 according to this embodiment. Figure 8 corresponds to Figure 3.

As shown in FIG. 8, the biological sound detection device 10 includes three elements 50A, 50B, and 50C. The elements 50A and 50B have the same configuration as the preceding embodiment. The surface film 52C of the element 50C has a different acoustic impedance from the surface films 52A and 52B. The surface film 52C is formed using a material different from the surface films 52A and 52B. In other words, the total reflection angle of the surface film 52C is different from the surface films 52A and 52B. As an example, the total reflection angle of the surface film 52C is larger than those of the surface films 52A and 52B.

Figure 9 shows the difference region of the attenuation characteristics of elements 50A, 50B, and 50C. Since the attenuation characteristics of the three elements 50A, 50B, and 50C are different from each other, two difference regions are created depending on the magnitude relationship of the total reflection angles. The first difference region corresponds to the difference region shown in the previous embodiment. In other words, it is the difference region between elements 50A and 50B. The second difference region is the difference region between elements 50B and 50C.

The signal processing unit 12 performs differential processing to subtract the output signal of element 50A from the output signal of element 50B, and differential processing to subtract the output signal of element 50B from the output signal of element 50C.

<Summary of the Second Embodiment>
According to this embodiment, the spatial resolution is improved. In other words, it is multi-channel. This makes it possible to detect a plurality of body sounds independently. Although an example having three elements is shown in FIG. 8, a configuration having four or more elements may be used. This makes it possible to improve the spatial resolution.

Third Embodiment
This embodiment is a modified example based on the previous embodiment, and the description of the previous embodiment can be used. In the previous embodiment, the surface films 52A and 52B are flat. Instead of this, a part of the surface of the surface films 52A and 52B may be curved or approximately curved.

Figure 10 is a perspective view showing surface membranes 52A and 52B in the body sound detection device 10 according to this embodiment. Figure 11 is a plan view showing surface membranes 52A and 52B. Figure 11 is a plan view seen from the front view direction and the side view direction shown in Figure 10.

The body sound detection device 10 of this embodiment has two elements 50A, 50B, similar to the configuration described in the preceding embodiment (Figure 3). The shapes of the surface films 52A, 52B of the two elements 50A, 50B are different from those of the preceding embodiment. Apart from this, the body sound detection device 10 has the same configuration as the body sound detection device 10 described in the preceding embodiment.

<Surface film>
As shown in Figures 10 and 11, the surface films 52A and 52B have a common structure. The surface films 52A and 52B have a curved surface in a portion of the surface. The surfaces (outer surfaces) of the surface films 52A and 52B are composed of a curved surface and a flat surface. The surface films 52A and 52B are substantially semicircular in plan view in the X direction. The surface films 52A and 52B extend in the X direction with a constant diameter. The surface films 52A and 52B are substantially semicircular columnar.

The surface films 52A and 52B have end faces 521 and 522 and an outer peripheral surface 523. The end faces 521 and 522 are flat, and the outer peripheral surface 523 is curved. The surface films 52A and 52B are arranged in the same direction when viewed from the detection unit 30 side, i.e., the Y direction.

<Directivity>
Next, the directivity of the body sound detection device 10 will be described with reference to Fig. 11 and Fig. 12. Fig. 12 shows the directivity of the body sound detection device 10 of this embodiment. The surface films 52A and 52B show cross-sectional shapes taken along line XII-XII in Fig. 10. In Fig. 12, the ψ direction is shown three-dimensionally to make the directivity easier to understand.

As shown in the upper part of Figure 11, the surface films 52A and 52B are approximately semicircular when viewed from the front view direction, i.e., the X direction. Therefore, regardless of the direction from which the body sound is incident, there is a portion in the opposing surface where the incident angle θ = 0 deg. Therefore, for the entire θ, there is no difference in energy propagation loss, i.e., no difference in attenuation, between elements 50A and 50B. This makes it possible to narrow the directivity in the φ direction.

As shown in the lower part of Figure 11, the surface films 52A and 52B are rectangular when viewed from the side view direction, i.e., the Z direction. Therefore, as in the previous embodiment, a difference in energy propagation loss, i.e., an attenuation difference, occurs between elements 50A and 50B at θ = 36 to 51 deg.

As a result, the body sound detection device 10 has directivity at φ=0deg, θ=36-51deg, and φ=180deg, θ=36-51deg, as shown in FIG. 12.

However, by adopting a curved surface, a new rotation axis of the directivity is generated. Specifically, the reference line SL shown by the dashed line in FIG. 12 is the new rotation axis. The reference line SL is perpendicular to the normal line NL. The reference line SL is perpendicular to the semicircular end faces 521, 522. The reference line SL passes through the center of the circle corresponding to the semicircle. As shown in FIG. 12, the body sound detection device 10 has a directivity of 0 to 180 deg in the direction around the axis of the reference line SL, that is, in the ψ direction. The ψ direction is the circumferential direction of the semicircle.

<Summary of the Third Embodiment>
According to the body sound detection device 10 of this embodiment, the surface films 52A, 52B of the two elements 50A, 50B have different acoustic impedances as in the previous embodiment, and a part of the surface is curved. In this way, by providing a curved surface, it is possible to prevent an attenuation difference between the elements 50A, 50B and narrow the directivity. In particular, since a part of the surface facing the detection unit 30 is curved, it is possible to narrow the directivity in the direction facing the detection unit 30. In other words, it is possible to substantially realize a narrower directivity.

<Modification>
The shape of the surface films 52A and 52B having a curved surface is not limited to the above-mentioned example. For example, in the example shown in FIG. 13, the end portion on the end face 521 side in the structure shown in FIG. 10 is curved. FIG. 13 is a perspective view showing a modified example, and corresponds to FIG. 10. As shown in FIG. 13, the surface films 52A and 52B have an end face 521A instead of the end face 521. The end face 522 and the outer peripheral surface 523 are similar to the configuration shown in FIG. 10. The end face 521A is a curved surface. The end face 521A has a shape equivalent to approximately 1/4 of a sphere.

Figure 14 corresponds to Figure 11. Figure 14 is a plan view seen from the front view direction and the side view direction shown in Figure 13. As shown in the upper part of Figure 14, the shape seen from the front view direction, i.e., the X direction, is the same as that of Figure 10. As shown in the lower part of Figure 14, the shape seen from the side view direction, i.e., the Z direction, includes a curved surface. This makes it possible to prevent attenuation differences from occurring on the end surface 521A side, i.e., φ = 0 deg, θ = 36 to 51 deg.

Figure 15 shows the directivity of the body sound detection device 10 equipped with the surface membranes 52A and 52B shown in Figure 13. The surface membranes 52A and 52B show a cross-sectional shape along the line XV-XV in Figure 13. Figure 15 corresponds to Figure 12 and shows the ψ direction three-dimensionally. As shown in Figure 15, the configuration of this modified example has directivity at φ = 180 deg and θ = 36 to 51 deg. In the ψ direction, it has directivity of 0 to 180 deg. In this way, it is possible to further narrow the directivity compared to the configuration shown in Figure 10.

The curved shape and position of the curved surface of the surface film 52 are not limited to the above example. By having a curved surface as part of the surface, it is possible to prevent differences in attenuation between elements 50A and 50B, thereby narrowing the directivity. Also, the same effect can be achieved by using an approximate curved surface that approximates the curved surface with multiple faces instead of the curved surface. In other words, the surface films 52A and 52B need only be similar in shape to each other, be arranged in the same direction when viewed from the detection unit 30 side, and include a curved surface or an approximate curved surface as part of each surface. As long as they are similar in shape, they may be different in size.

The number of elements 50 included in the body sound detection device 10 is not limited to two. The above configuration may be applied to three or more elements 50.

Fourth Embodiment
This embodiment is a modification based on the preceding embodiment, and the description of the preceding embodiment can be used. In the preceding embodiment, the surface film 52 of each element 50 is made of a single material. Instead of this, in some of the multiple elements 50, the surface film 52 may be made of two or more materials having different acoustic impedances.

Figure 16 is a perspective view showing the surface membranes 52A, 52B in the body sound detection device 10 according to this embodiment. The body sound detection device 10 of this embodiment also includes two elements 50A, 50B, similar to the configuration described in the preceding embodiment (Figure 3). In the two elements 50A, 50B, the material configuration of the surface membrane 52A differs from that of the preceding embodiment. Apart from this point, the body sound detection device 10 has the same configuration as the body sound detection device 10 described in the preceding embodiment.

<Surface film>
As shown in Fig. 16, the surface films 52A and 52B have a common shape. The surface films 52A and 52B have a shape similar to that of the surface films 52A and 52B shown in Fig. 13. In other words, the surface films 52A and 52B have an end surface 521A, an end surface 522, and an outer circumferential surface 523.

Surface film 52A is made of two materials 524 and 525. Surface film 52B is made of material 525. Materials 524 and 525 have different acoustic impedances. In this embodiment, material 524 is nylon, and material 525 is polyethylene. In other words, surface film 52A in this embodiment is made using the material of surface film 52A and the material of surface film 52B shown in the previous embodiment. Surface film 52B is made of a single material, as in the previous embodiment.

In the surface film 52A, material 525 forms the main portion, and material 524 is provided in a portion. Material 524 is provided in a columnar portion of constant diameter, and forms part of the outer circumferential surface 523. Material 524 is provided from one end to the other end of the columnar portion of constant diameter in the extension direction (X direction) of the surface film 52A. Material 524 is provided in a position on the outer circumferential surface 523 that includes the apex on the detection unit 30 side. Material 524 has a width in the Z direction that is sufficiently narrow compared to the width of the surface film 52A.

<Directivity>
Next, the directivity of the body sound detector 10 will be described with reference to Fig. 17. Fig. 17 shows the directivity of the body sound detector 10 of this embodiment. The surface films 52A and 52B show cross-sectional shapes taken along line XVII-XVII in Fig. 16.

As described above, the surface films 52A and 52B have a common shape and are largely made of the same material 525. In the portion made of material 525, there is no difference in attenuation between the elements 50A and 50B.

On the other hand, an attenuation difference occurs due to the difference in acoustic impedance between the portion of the surface film 52A that is made of the substance 524 and the corresponding portion of the surface film 52B. However, since the placement of the substance 524 is limited to a portion of the surface film 52A, the directivity can be narrowed compared to the example shown in FIG. 13. Specifically, the directivity in the ψ direction can be narrowed. As a result, the body sound detection device 10 has directivity of ψ = 90 deg, φ = 180 deg, and θ = 36 to 51 deg.

<Summary of the Fourth Embodiment>
According to the body sound detection device 10 of the present embodiment, of the two elements 50A and 50B, the surface film 52A of the element 50A is made of two materials 524 and 525 having different acoustic impedances. This makes it possible to narrow the area in which an attenuation difference occurs between the two elements 50A and 50B. This makes it possible to narrow the directivity compared to a configuration in which the surface films 52A and 52B made of a single material have different acoustic impedances.

<Modification>
In the surface film 52A, the arrangement of the two substances 524 and 525 is not limited to the example described above.

An example in which surface film 52A is made of materials 524 and 525 and surface film 52B is made of material 525 has been shown, but this is not limiting. Surface film 52A may be made of material 524 and surface film 52B may be made of materials 524 and 525.

The shape of the surface films 52A and 52B is not limited to the above example. It may be applied to the configuration shown in FIG. 10. For example, as shown in FIG. 18, the above configuration may be applied to the surface films 52A and 52B that are composed only of flat surfaces. FIG. 18 is a plan view of the elements 50A and 50B as seen from the detection unit 30 side, that is, from the Y direction. The surface films 52A and 52B are rectangular parallelepipeds that form an approximately square shape in a plan view in the Y direction. As with the configuration shown in FIG. 16, the surface film 52A is composed of two substances 524 and 525, and the surface film 52B is composed of the substance 525. The substance 524 forms a part of the opposing surface of the surface film 52A. The substance 524 is provided from one end to the middle of the surface film 52A in the X direction. The substance 524 has a width that is sufficiently narrower than the width of the surface film 52A in the Z direction.

Figure 19 shows the directivity of the body sound detection device 10 equipped with the surface films 52A and 52B shown in Figure 18. The surface films 52A and 52B show a cross-sectional shape along line XIX-XIX in Figure 18. As shown in Figure 19, the configuration of this modified example has directivity in φ=0 deg, θ=36-51 deg and φ=180 deg, θ=36-51 deg. In this way, by limiting the placement of the substance 524 to a portion of the surface film 52A, it is possible to narrow the directivity compared to the example shown in Figure 3. Specifically, it is possible to narrow the directivity in the φ direction.

The number of elements 50 included in the body sound detection device 10 is not limited to two. It may be applied to a configuration including three or more elements 50. For example, in a configuration including three elements 50 as shown in FIG. 8, the surface film 52 of one of the elements 50 may be made of three materials, and the surface film 52 of the remaining elements 50 may be made of a single material.

In other words, in some of the multiple elements 50, the surface film 52 may be made of two or more materials with different acoustic impedances.

Fifth Embodiment
This embodiment is a modification of the preceding embodiment as a basic form, and the description of the preceding embodiment can be used. In the preceding embodiment, narrow directivity is realized by using materials with different acoustic impedances. Alternatively, narrow directivity may be realized by the arrangement of the surface film 52.

Figure 20 is a partial cross-sectional view showing the periphery of the element 50 in the biological sound detection device 10 according to this embodiment. Figure 20 corresponds to Figure 3. The biological sound detection device 10 according to this embodiment also includes two elements 50A and 50B, similar to the configuration described in the preceding embodiment (Figure 3). The surface films 52A and 52B of the elements 50A and 50B are formed using a common material (substance). In other words, the acoustic impedances of the surface films 52A and 52B are equal to each other. The surface films 52A and 52B have a total reflection angle. As in the first embodiment, the surface films 52A and 52B are flat films with a substantially uniform thickness.

The angle between the opposing surface of the surface film 52 and the normal NL is different between elements 50A and 50B. In element 50A, the angle between the surface of surface film 52A and the normal NL is A1. On the other hand, in element 50B, the angle between the surface of surface film 52B and the normal NL is A2. Angles A1 and A2 are different from each other. For example, angle A2 is larger than angle A1. As an example, in this embodiment, the upper surfaces of element bodies 51A and 51B are inclined surfaces, and the surfaces of surface films 52A and 52B laminated on the upper surfaces are also inclined with respect to the ZX plane. The angles A1 and A2 are different due to the different inclination directions.

<Summary of Fifth Embodiment>
As described above, the angles A1, A2 between the opposing surfaces of the surface films 52A, 52B and the normal NL are different from each other, so that the angles of incidence of the body sound (acoustic signal) incident from a predetermined direction are different between the elements 50A, 50B. Specifically, the angle of incidence with respect to the normal NA in the element 50A is θa. On the other hand, the angle of incidence with respect to the normal NB in the element 50B is θb. The angle of incidence θb is different from the angle of incidence θa. In this way, the angles of incidence θa, θb of the two elements 50A, 50B are different from the angles of incidence with respect to the body sound from the same direction, i.e., the common body sound.

Therefore, a difference occurs between the output signals of elements 50A and 50B according to the difference between the angles A1 and A2 with respect to the normal NL. Because a difference occurs between the output signals of elements 50A and 50B, a narrow directivity can be achieved.

In this embodiment, the angles A1, A2 between the opposing surfaces of the surface films 52A, 52B and the normal line NL are made different, so that the angles of total reflection of the acoustic signal (body sound) based on the normal line NL in the two elements 50A, 50B are made different from each other. By simply adjusting the angle between the opposing surfaces and the normal line NL, it is possible to separate and detect body sound with a simple structure.

Adjustment of angles A1 and A2 is not limited to the inclined structure of element body 51. For example, angles A1 and A2 may be adjusted to be different depending on the support shape of housing 20 that supports element 50.

The number of elements 50 included in the body sound detection device 10 is not limited to two. The above configuration may be applied to three or more elements 50.

In this embodiment, an example has been shown in which the surface films 52A and 52B are made of the same material, but this is not limiting. The surface films 52A and 52B may be made of different materials. In other words, surface films 52A and 52B with different acoustic impedances may be used, and the angles they make with the normal line NL may be different. A combination of different materials and different angles may be used to achieve a narrower directivity.

Other Embodiments
The disclosure in this specification and drawings, etc. is not limited to the exemplified embodiments. The disclosure includes the exemplified embodiments and modifications by those skilled in the art based thereon. For example, the disclosure is not limited to the combination of parts and/or elements shown in the embodiments. The disclosure can be implemented by various combinations. The disclosure can have additional parts that can be added to the embodiments. The disclosure includes the omission of parts and/or elements of the embodiments. The disclosure includes the substitution or combination of parts and/or elements between one embodiment and another embodiment. The disclosed technical scope is not limited to the description of the embodiments. Some disclosed technical scopes are indicated by the description of the claims, and should be interpreted as including all modifications within the meaning and scope equivalent to the description of the claims.

The disclosure in the specification and drawings, etc. is not limited by the claims. The disclosure in the specification and drawings, etc. encompasses the technical ideas described in the claims, and extends to more diverse and extensive technical ideas than the technical ideas described in the claims. Therefore, various technical ideas can be extracted from the disclosure in the specification and drawings, etc., without being bound by the claims.

When an element or layer is referred to as being "on," "coupled," "connected," or "bonded," it may be directly coupled, connected, or bonded to another element or layer, and intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly coupled," "directly connected," or "directly bonded" to another element or layer, no intervening elements or layers are present. Other words used to describe relationships between elements should be construed in a similar manner (e.g., "between" vs. "directly between," "adjacent" vs. "directly adjacent," etc.). As used in this specification, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Spatially relative terms such as "inside," "outside," "back," "bottom," "low," "top," "top," and the like are utilized herein for ease of description to describe the relationship of one element or feature to other elements or features as depicted in the figures. Spatially relative terms may be intended to encompass different orientations of the device during use or operation in addition to the orientation depicted in the drawings. For example, if the device in the figures is turned over, elements described as "below" or "directly below" other elements or features would be oriented "above" the other elements or features. Thus, the term "bottom" can encompass both an orientation of top and bottom. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used in this specification would be interpreted accordingly.

Applications of the biological sound detection device 10 are not limited to detecting biological sounds of a vehicle occupant 110. For example, it may be used in an electronic stethoscope.

Although an example has been shown in which multiple elements 50 are accommodated in a common accommodation space, this is not limiting. For example, as shown in FIG. 21, the accommodation space may be divided for each element 50. In other words, multiple body sound detection sensors 11 may be provided, with one element 50 arranged in one accommodation space. In FIG. 21, the body sound detection device 10 is provided with a body sound detection sensor 11A including an element 50A, and a body sound detection sensor 11B including an element 50B.

In the above example, the element bodies 51 of the multiple elements 50 are provided independently, but this is not limiting. For example, as shown in FIG. 22, the element bodies 51A and 51B of the elements 50A and 50B may be provided integrally. Even if the element bodies 51A and 51B are integrated, each element 50 is configured to output an electrical signal independently.

As shown in FIG. 23, the signal processing unit 12 may be disposed in the housing space of the body sound detection sensor 11.

10...Body sound detection device, 11, 11A, 11B...Body sound detection sensor, 12...Signal processing unit, 20...Housing, 21...Case, 211...Bottom wall, 22...Cover, 30...Detection unit, 40...Medium, 50, 50A, 50B, 50C...Element, 51, 51A, 51B, 51C...Element body, 52, 52A, 52B, 52C...Surface film, 521, 521A, 522...End surface, 523...Outer surface, 524, 525...Material, 100...Seat, 101...Seating portion, 102...Backrest portion, 103...Seat belt, 110...Occupant

Claims (6)

A housing (20);
A detection unit (30) that provides an accommodation space together with the housing and detects an acoustic signal that is a body sound;
A medium (40) disposed in the accommodation space and having an acoustic impedance closer to that of water than that of air;
a plurality of elements (50, 50A, 50B, 50C) disposed in the accommodation space and configured to convert the acoustic signal transmitted through the detection unit and the medium into an electric signal;
The plurality of elements each have a surface film (52, 52A, 52B, 52C) that has a larger acoustic impedance than the medium and forms a surface facing the detection unit,
The plurality of elements have mutually different total reflection angles of the acoustic signal based on a normal line perpendicular to an arrangement direction of the plurality of elements. The body sound detection device according to claim 1, wherein the acoustic impedance of the surface film is different for each of the elements. The body sound detection device according to claim 1, wherein the surface film of some of the elements is made of two or more materials with different acoustic impedances. In the plurality of elements,
The surface films are similar in shape and are arranged in the same direction;
4. The body sound detecting device according to claim 2, wherein a portion of a surface of each of the surface membranes is a curved surface or an approximately curved surface. The body sound detection device according to claim 1, wherein the angles between the facing surface and the normal line are different for each of the elements. The body sound detection device according to any one of claims 1 to 5, comprising a signal processing unit (12) that calculates the difference between the output signals of the multiple elements.

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