WO2019240118A1

WO2019240118A1 - Sound acquisition device

Info

Publication number: WO2019240118A1
Application number: PCT/JP2019/023058
Authority: WO
Inventors: 俊一里見; 清水　勇治; 隆徳垣内; 長谷部　剛
Original assignee: パイオニア株式会社
Priority date: 2018-06-15
Filing date: 2019-06-11
Publication date: 2019-12-19
Also published as: JP7112489B2; JPWO2019240118A1

Abstract

Provided is, for example, a sound acquisition device capable of reducing noise while suppressing time delay and energy consumption. This sound acquisition device (10) comprises a vibration detection unit (120) and support member (140). The vibration detection unit (120) comprises one or more sensor elements (122) and has a plurality of detection axes (123). The support member (140) supports the vibration detection unit (120). The plurality of detection axes (123) are not parallel to each other and are inclined in relation to a first surface (101) facing a subject part (90).

Description

Sound acquisition device

The present invention relates to a sound acquisition device.

In devices that electrically acquire sound from a target such as an electronic stethoscope, it is required to reduce noise noise from other than the target.

Patent Document 1 discloses a biological sound in which a microphone that acquires biological noise including environmental noise and a microphone that acquires environmental noise are provided in a chest piece, and signals from those microphones are processed to reduce environmental noise. Obtaining a signal is described.

Japanese Unexamined Patent Publication No. 2016-67857

However, the technique of Patent Document 1 requires high-order algorithm processing to reduce environmental noise. As a result, the processing required time and power.

An example of a problem to be solved by the present invention is to provide a sound acquisition device capable of reducing noise while suppressing time delay and energy consumption.

The invention described in claim 1
A vibration detecting unit including one or more sensor elements and having a plurality of detection axes;
A support member for supporting the vibration detection unit,
The plurality of detection axes are non-parallel to each other, and are sound acquisition devices that are inclined with respect to a first surface facing the target portion.

The above-described object and other objects, features, and advantages will be further clarified by a preferred embodiment described below and the following drawings attached thereto.

It is a figure which illustrates typically the composition of the sound acquisition device concerning an embodiment. It is a figure for demonstrating the detection of the sound from a target part. It is a figure for demonstrating the detection of an external sound. 1 is a block diagram illustrating a functional configuration of a sound acquisition device according to Embodiment 1. FIG. It is a figure which illustrates the structure of the sound acquisition apparatus which concerns on Example 1. FIG. It is sectional drawing which expands and illustrates the supporting member and vibration detection part vicinity of a sound acquisition apparatus. It is a figure for demonstrating operation | movement of a sensor element. (A) And (b) is a figure which illustrates the relationship between (theta) and the directivity of a vibration detection part. FIG. 10 is a schematic diagram for explaining a processing method of a processing unit according to the second embodiment. 7 is a cross-sectional view illustrating the structure of a sound acquisition device according to Example 3. FIG. It is a figure for demonstrating the relationship between the structure of a sound acquisition apparatus, and the detection sensitivity of an absorption component. It is a figure which shows the modification of the support member and pressure sensor of a sound acquisition apparatus. (A) to (c) is a diagram illustrating a plurality of detection axes according to the fourth embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

In the following description, the processing unit 110 of the sound acquisition device 10 is not a hardware unit configuration but a functional unit block. The processing unit 110 of the sound acquisition apparatus 10 includes hardware and software mainly for a CPU of a computer, a memory, a program loaded in the memory, a storage device such as a flash memory for storing the program, and a network connection interface. Realized by any combination. There are various modifications of the implementation method and apparatus.

FIG. 1 is a diagram schematically illustrating the configuration of a sound acquisition device 10 according to the embodiment. The sound acquisition device 10 according to the present embodiment includes a vibration detection unit 120 and a support member 140. The vibration detection unit 120 includes one or more sensor elements 122 and has a plurality of detection axes 123. The support member 140 supports the vibration detection unit 120. The plurality of detection axes 123 are non-parallel to each other and are inclined with respect to the first surface 101 facing the target portion 90. This will be described in detail below.

The sound acquisition device 10 according to the present embodiment is a device that selectively acquires sound from the target unit 90 by pressing the first surface 101 against the target unit 90. Sound from the target unit 90 is transmitted to the support member 140 via the first surface 101 and detected by the vibration detection unit 120. On the other hand, external sound other than the target unit 90 is transmitted to the housing 130 of the sound acquisition device 10. This external sound can also be detected by the vibration detection unit 120 as noise. Examples of external sounds include peripheral environment sounds such as equipment operation sounds, talking voices and footsteps, and user-derived sounds such as operation sounds and user's body sounds. Ambient environmental sound mainly propagates in the air and reaches the housing 130. On the other hand, the user-derived sound is generated directly on the surface of the housing 130 by gripping or rubbing the housing 130.

Here, the vibration detection unit 120 includes sensor elements 122 a and sensor elements 122 b as a plurality of sensor elements 122. The detection axis 123 a of the sensor element 122 a and the detection axis 123 b of the sensor element 122 b are non-parallel to each other and are inclined with respect to the first surface 101. By doing so, as described below, the target sound from the target unit 90 and the external sound are mechanically separated, and noise can be reduced by simple signal processing.

FIG. 2 is a diagram for explaining detection of sound from the target unit 90, and FIG. 3 is a diagram for explaining detection of external sound.

The vibration direction of the target sound from the target unit 90 is perpendicular to the first surface 101 as indicated by a white arrow in FIG. And the vibration of the direction perpendicular | vertical with respect to the 1st surface 101 appears in the same phase in the detection signal of the detection axis 123a, and the detection signal of the detection axis 123b, as shown by the waveform of a and b in this figure.

On the other hand, part of the external sound is absorbed by the housing 130 and propagates through the housing 130 as indicated by the black arrows in FIG. As a result, the external sound absorbed by the housing 130 becomes a vibration in a direction parallel to the first surface 101 in the support member 140, as indicated by white arrows in the figure. And the vibration of the horizontal direction with respect to the 1st surface 101 appears with an antiphase in the detection signal of the detection axis 123a, and the detection signal of the detection axis 123b, as shown by the waveform of a and b in this figure.

From the above, for example, by adding the detection signal of the detection shaft 123a and the detection signal of the detection shaft 123b, the component of the target sound is amplified and the component of the external sound is attenuated. That is, the S / N ratio obtained by dividing the target sound component by the external sound component is improved.

As described above, according to the present embodiment, the plurality of detection axes 123 are non-parallel to each other and are inclined with respect to the first surface 101 facing the target portion 90. Therefore, noise can be reduced by suppressing the time delay and energy consumption by simple processing of the detection signal.

(Example 1)
FIG. 4 is a block diagram illustrating the functional configuration of the sound acquisition device 10 according to the first embodiment. The sound acquisition device 10 according to the present example has the same configuration as the sound acquisition device 10 according to the embodiment.

The sound acquisition apparatus 10 according to the present embodiment further includes a processing unit 110 that generates sound data by processing the output from the vibration detection unit 120.

The sound acquisition device 10 is an electronic stethoscope, for example, and further includes an output unit 192 that outputs sound based on the sound data generated by the processing unit 110.

However, the sound acquisition device 10 may be a device that outputs the signal acquired by the vibration detection unit 120 to the outside of the sound acquisition device 10 in a wired or wireless manner. In addition, sound data generated by the processing unit 110 of the sound acquisition device 10 or outside the sound acquisition device 10 is not limited to being output as sound, but may be used for analysis or displayed on a display as a waveform. May be. In the sound acquisition device 10, it is possible to convert the acquired sound into an electrical signal once, and to convert it into data by, for example, AD conversion and record it.

For example, by performing specific arithmetic processing on the data acquired in this way, it is possible to find a possibility of highly accurate diagnosis regarding a living body or a structure. Here, in the analysis, the acquired data is all, and it is difficult to determine whether the data is correct data. Therefore, in the analysis of data including noise, there is a possibility that the diagnostic accuracy is impaired. Therefore, it can be said that the necessity of reducing noise by electrical processing is particularly high.

The target unit 90 is not particularly limited, but may be a part of a structure such as a bridge, a building, a tunnel, a machine, or a living body.

FIG. 5 is a diagram illustrating the structure of the sound acquisition device 10 according to the first embodiment. In this figure, the grip part 100 has shown the cross section. FIG. 6 is an enlarged cross-sectional view illustrating the vicinity of the support member 140 and the vibration detection unit 120 of the sound acquisition device 10. In this figure, the detection axis 123a and the detection axis 123b are indicated by broken lines.

The sound acquisition device 10 includes a grip unit 100, an earphone unit 190, and a cable 180. When the sound acquisition device 10 is an electronic stethoscope, the grip unit 100 is a chest piece. The earphone unit 190 is provided with an output unit 192. The output unit 192 is a speaker. The cable 180 connects the grip unit 100 and the earphone unit 190 physically and electrically. However, the sound acquisition device 10 does not include the cable 180, and the grip unit 100 and the output unit 192 may be connected by wireless communication.

The user of the sound acquisition device 10 wears the earphone unit 190, grasps the grip unit 100, and presses the first surface 101 against the target unit 90. Then, in the grip unit 100, the vibration detection unit 120 detects sound as vibration, and the processing unit 110 processes the output of the vibration detection unit 120 to generate sound data. The sound data is input to the earphone unit 190 via the cable 180, and a sound based on the sound data is output from the output unit 192. Thus, the user can hear the sound from the target unit 90.

The outer shell of the grip part 100 is mainly composed of a housing 130. The housing 130 is provided with an opening for capturing the target sound from the target unit 90. This opening is covered with a diaphragm 150. The housing 130 is provided with an opening for arranging the switch 112.

In the internal space of the grip part 100 constituted by the housing 130 and the diaphragm 150, a vibration detection part 120, a support member 140, a battery 111, and a circuit board 113 are arranged. The circuit board 113 includes a circuit capable of driving the sensor element 122 and performing signal processing. The circuit board 113 is driven by the power supplied from the battery 111 and functions as the processing unit 110. The switch 112 controls the operation of the processing unit 110 and the like.

The battery 111, the switch 112, and the circuit board 113 are fixed to the housing 130. In addition, each sensor element 122 is electrically connected to the circuit board 113 in a state where the vibration of the sensor element 122 is not hindered. Then, the output signal of each sensor element 122 is input to the circuit board 113. Further, an output signal from the circuit board 113 is input to the earphone unit 190. The output signal from the circuit board 113 includes sound data or a sound signal based on the sound data.

The processing unit 110 is realized by a digital signal processor (DSP) or a central processing unit (CPU), for example. By using a DSP, high-speed processing is possible. For example, the processing unit 110 generates sound data by adding detection signals for two detection axes 123 constituting a pair described later. As described above, the processing unit 110 can generate sound data by a simple process. Therefore, output from the output unit 192 can be performed with a short delay time from the acquisition of sound in the target unit 90. In particular, when the sound acquisition device 10 is an electronic stethoscope, a large delay causes a sense of incongruity during use, and thus it is important to realize a short delay time. In addition, the simplicity of the process contributes to suppression of erroneous signal processing. Furthermore, since the processing is simple, the energy consumption of the DSP can be kept low, which contributes to a reduction in power consumption of the apparatus.

In the processing unit 110, processing such as digital / analog conversion, analog / digital conversion, filtering, and amplification may be appropriately performed. For example, the processing unit 110 may have a filter function that can switch the auscultation frequency band and a correction function that corrects individual performance variation of the sensor element 122.

The switch 112 is a power switch for starting the sound acquisition device 10, a switch for auscultation frequency mode switching of the sound acquisition device 10, or the like.

The earphone unit 190 may further include a digital / analog conversion circuit, a filter, an amplifier, and the like as necessary. Sound is output from the output unit 192 based on the output signal from the circuit board 113 input to the earphone unit 190.

The housing 130 is made of metal or resin. When the housing 130 is made of metal, it is suitable for noise reduction because of high rigidity and high sound insulation. On the other hand, when the target part 90 is a part of a living body, the housing 130 is particularly preferably a resin. When used for a living body, it is necessary to avoid the generation of static electricity. However, if the housing 130 is made of resin, static electricity is hardly generated. Therefore, no special countermeasures against static electricity are required. Further, according to the present embodiment, since the noise can be reduced by the processing unit 110, the casing 130 does not require special high rigidity and sound insulation. Therefore, the resin casing 130 can be suitably used.

The diaphragm 150 has a cap shape, is fixed to the housing 130, and covers an opening for capturing the target sound of the housing 130. The first surface 101 is a part of the outer surface of the sound acquisition device 10. In the present embodiment, the first surface 101 is a surface facing the target portion 90 of the diaphragm 150.

When acquiring sound, the diaphragm 150 is brought into contact with or close to the target portion 90. The diaphragm 150 is exposed to the outside of the sound acquisition device 10 and is a vibrating body for transmitting vibration caused by the target sound to the support member 140 and the vibration detection unit 120. When the target part 90 is a part of a living body, the diaphragm 150 is preferably made of a material having biocompatibility. Examples of the material having biocompatibility include silicone. Note that the diaphragm 150 may have a multilayer structure including a protective film or the like.

It should be noted that pressing the first surface 101 against the target portion 90 means bringing the first surface 101 into contact with or approaching the target portion 90. For example, clothes or the like may be interposed between the first surface 101 and the target unit 90 at the time of sound acquisition. However, when the sound is acquired, the diaphragm 150 is pressed toward the support member 140 so that the target sound is transmitted to the support member 140. Further, the diaphragm 150 may be integrated with the support member 140.

The support member 140 is a member that supports the vibration detection unit 120. In the example of FIG. 6, the vibration detection unit 120 includes a plurality of sensor elements 122. The support member 140 is provided with a support surface 145 that supports each of the plurality of sensor elements 122. The plurality of support surfaces 145 are oblique with respect to the first surface 101 and face different directions. Here, the detection axis 123 of the sensor element 122 supported by the support surface 145 may be perpendicular or parallel to the support surface 145. FIG. 6 shows an example in which the detection shaft 123 is perpendicular to the support surface 145.

More specifically, the support member 140 has a base portion 142 and a convex portion 144 that protrudes from the base portion 142 to the side opposite to the first surface 101 side. A support surface 145 is provided on the side surface of the convex portion 144. Moreover, the outer peripheral part of the base part 142 is physically connected to the housing | casing 130 of the grip part 100 which a user touches. The support member 140 is a resin member, for example.

In the example of FIG. 6, a concave portion is provided on the surface of the outer edge portion of the base portion 142 on the diaphragm 150 side. And the convex part inserted in the recessed part is provided in the part connected with the supporting member 140 of the housing | casing 130. As shown in FIG. The housing 130 and the support member 140 are connected by joining the concave and convex portions. With such a structure, lateral vibration from the housing 130 is transmitted to the support member 140. The housing 130 may be provided with a recess, and the support member 140 may be provided with a protrusion that fits into the recess. Further, the support member 140 and the housing 130 may be connected by screws, or the support member 140 and the housing 130 may be integrated members.

In the example of FIG. 6, the base portion 142 has a disk shape with a non-uniform thickness. The base portion 142 is provided with a recess in which a part of the sensor element 122 is disposed. The convex portion 144 has a shape in which one side surface of a triangular prism having a right isosceles triangle as a bottom surface is joined to the base portion 142. The two side surfaces of the triangular prism perpendicular to each other face the side opposite to the first surface 101 and function as the support surface 145. The support member 140 has a plane-symmetric structure. Here, the symmetry plane is perpendicular to the first surface 101 and passes between the sensor element 122a and the sensor element 122b. The sensor element 122a and the sensor element 122b are also arranged symmetrically with respect to this symmetry plane.

In the example of this figure, the sound acquisition device 10 further includes a pressure sensor 152 that detects the pressure from the target portion 90 to the diaphragm 150 between the diaphragm 150 and the support member 140. Then, the processing unit 110 controls the generation timing of the sound data using the output of the pressure sensor 152.

In the example of this figure, the surface of the support member 140 on the diaphragm 150 side is in close contact with the pressure sensor 152, and the surface of the pressure sensor 152 opposite to the support member 140 is in close contact with the diaphragm 150. The pressure sensor 152 is provided between the support member 140 and the pressure sensor 152 as a whole, and the support member 140 and the diaphragm 150 are not in direct contact with each other.

The pressure sensor 152 is, for example, a contact sensor. Indirect or direct contact of the diaphragm 150 with the target portion 90 can be detected by the pressure sensor 152. When the pressure sensor 152 detects a pressure equal to or higher than a predetermined reference, the processing unit 110 can determine that the grip unit 100 is pressed against the target unit 90. Information indicating the reference is held in the storage unit 115 provided on the circuit board 113 of the sound acquisition device 10, and can be read and used by the processing unit 110. Note that the pressure sensor 152 may output a signal indicating the presence or absence of pressure instead of outputting a signal indicating the pressure value. In this case, the processing unit 110 can determine that the grip unit 100 is pressed against the target unit 90 when a signal with pressure is output from the pressure sensor 152.

For example, the processing unit 110 generates sound data while the grip unit 100 is pressed against the target unit 90, and stops generating sound data while the grip unit 100 is not pressed against the target unit 90. In this way, power consumption of the battery 111 can be suppressed. Note that generation of sound data may be continued for a predetermined time (for example, several seconds) even after the grip unit 100 is separated from the target unit 90.

The support member 140 will be described in more detail. Each sensor element 122 is fixed to the support member 140, but is not directly fixed to the housing 130. Therefore, the vibration of the support member 140 is detected by the sensor element 122.

As described above, when the first surface 101 is pressed against the target portion 90, the diaphragm 150 is pressed toward the surface of the support member 140 on the diaphragm 150 side, and sound (vibration) from the target portion 90 is transmitted to the support member 140. Is transmitted to. As described in the embodiment, the target sound from the target portion 90 is vibration in a direction perpendicular to the first surface 101 in the support member 140.

On the other hand, the outer peripheral portion of the base portion 142 is physically connected to the casing 130 of the grip portion 100 that is touched by the user. Therefore, sound (vibration) from the housing 130 is vibration in a direction parallel to the first surface 101 in the support member 140. Since the external sound is acquired through the housing 130 and the support member 140 in the sound acquisition device 10, it is not necessary to separately provide a microphone for external sound acquisition and a sound capturing hole. As a result, the grip of the grip 100 is maintained and the durability is enhanced, and the grip 100 is easy to clean and clean.

The sensor element 122 is, for example, an acceleration sensor. That is, when the entire sensor element 122 is shaken, the shake is detected as vibration. The detection axis 123 of the sensor element 122 is an axis that is principally detected by the sensor element 122 in principle, and is the axis with the highest sensitivity. The detection shaft 123 is predetermined for each sensor element 122.

FIG. 7 is a diagram for explaining the operation of the sensor element 122. In this figure, the cross-sectional schematic diagram of the sensor element 122 and the relationship of the output waveform with respect to the movement of the sensor element 122 are shown. A diaphragm 124 is provided inside the sensor element 122. One end or both ends of the diaphragm 124 are fixed to the housing of the sensor element 122, and the diaphragm 124 bends in the axial direction according to the vibration of the sensor element 122. This amount of deflection is converted into an electric signal by, for example, electrostatic capacity or piezoelectricity. As a result, a signal corresponding to the vibration (acceleration) of the sensor element 122 is output from the sensor element 122. The polarity of the output of the sensor element 122 corresponds to the direction of acceleration with the detection axis 123 as a reference. In the example of this figure, the detection shaft 123 is parallel to the bending direction of the diaphragm 124.

Each sensor element 122 may have one or more detection axes 123 depending on the internal structure. When each sensor element 122 has one detection axis 123, the vibration detection unit 120 is realized using a plurality of sensor elements 122. In this case, in particular, the sound acquisition device 10 can be configured by freely setting the directions of the plurality of detection axes 123. 5 and 6 show examples in which each sensor element 122 has one detection axis 123 as described above.

On the other hand, when the sensor element 122 having two or more detection axes 123 is used, the vibration detection unit 120 may be configured by one sensor element 122. In this case, the sensor element 122 is, for example, a 2-axis sensor or a 3-axis sensor, and the detection axes 123 are orthogonal to each other. Then, the support member 140 may support the sensor element 122 so that the plurality of detection shafts 123 are all inclined with respect to the first surface 101.

The plurality of detection axes 123 of the vibration detection unit 120 and the processing of the processing unit 110 will be described in detail below. As described above, the plurality of detection axes 123 are not parallel to each other and are oblique to the first surface 101. That is, the detection axis 123 is inclined with respect to the normal line of the first surface 101.

Here, the plurality of detection axes 123 preferably include a pair of two detection axes 123 whose projections onto the first surface 101 are parallel to each other. Moreover, it is preferable that the angle with respect to the 1st surface 101 of the two detection axes 123 which comprise a pair is mutually equal. In such a pair, the vibration component in the direction parallel to the first surface 101 acts on the sensor element 122 as a vibration component having an opposite phase and the same strength. Therefore, the vibration component in the direction parallel to the first surface 101, that is, the component of the external sound can be effectively reduced by simply adding the detection signals for the two detection axes 123.

Note that the directions of the two detection axes 123 constituting the pair, that is, the detection polarities, are opposite to each other in the projection onto the first surface 101. The projections of the two detection axes 123 constituting the pair on the first surface 101 are preferably on the same straight line, but may not necessarily be on the same straight line.

When the plurality of detection shafts 123 are composed of one or more pairs, the vibration detection unit 120 has an even number of detection shafts 123.

FIG. 6 shows an example in which the detection axis 123a and the detection axis 123b are two detection axes 123 constituting a pair, and the angles with respect to the first surface 101 are equal to each other.

The angle θ formed by the two detection axes 123 constituting the pair is not particularly limited, but is preferably 60 ° or more and 120 ° or less, and preferably 75 ° or more and 105 ° from the viewpoint of the balance between sensitivity to the target sound and directivity. More preferably, it is 85 degrees or more and 95 degrees or less.

8A and 8B are diagrams illustrating the relationship between θ and the directivity of the vibration detection unit 120. FIG. In the example of FIG. 8A, θ is larger than that in the example of FIG. As shown in these figures, the larger the θ, the higher the directivity. That is, it is possible to acquire sound from a limited angle range. Thus, the directivity of the vibration detector 120 can be adjusted by the directivity of the sensor element 122 itself and the setting of θ. On the other hand, as θ is smaller, the target sound from the target portion 90, that is, the vibration component perpendicular to the first surface 101, can be acquired with higher sensitivity.

The processing unit 110 may further perform necessary processing in addition to adding the detection signals for the two detection axes 123 constituting the pair. For example, the processing unit 110 can perform processing for correcting characteristic variations such as sensitivity and frequency characteristics of the sensor element 122. Further, it is possible to perform processing for correcting a phase shift corresponding to the distance and frequency between the sensor elements 122, that is, a time shift. However, these processes are not dynamic signal processes but processes using fixed parameters, and the processes are not excessively complicated.

It is preferable that the distance between the plurality of sensor elements 122 is short. This is because in the noise cancellation by adding the detection signals, the residual error in the obtained sound data can be reduced by reducing the phase difference between the plurality of 122 detection signals. For example, assuming an effect on a component having a relatively low frequency (for example, 3 kHz or less) such as a body sound, the distance between the center of the sensor element 122a and the center of the sensor element 122b is preferably 10 mm or less.

As described above, according to the present example, as in the embodiment, the plurality of detection axes 123 are non-parallel to each other and are inclined with respect to the first surface 101 facing the target unit 90. Therefore, noise can be reduced by suppressing the time delay and energy consumption by simple processing of the detection signal.

(Example 2)
FIG. 9 is a schematic diagram for explaining the processing method of the processing unit 110 according to the second embodiment. The sound acquisition device 10 according to the present embodiment is the same as the sound acquisition device 10 according to the first embodiment except for the processing content performed by the processing unit 110.

In the present embodiment, the processing unit 110 generates sound data using the first transfer function G ₁ , the second transfer function G ₂ , and the output from the vibration detection unit 120. The first transfer function G ₁ is a transfer function when the sound S _N external to the sound acquisition device 10 is input and the sound component S _{pN in the} direction parallel to the first surface 101 in the vibration detection unit 120 is output. is there. The second transfer function G ₂ is a transfer when the sound _SN outside the sound acquisition device 10 is input and the sound component S _{vN in the} direction perpendicular to the first surface 101 in the vibration detection unit 120 is output. It is a function.

Note that the sound component in the direction parallel to the first surface 101 is a sound detected as a vibration component parallel to the first surface 101 by the vibration detection unit 120, that is, a detection signal of the first detection axis 123a. It is a sound detected as an antiphase component with respect to the detection signal of the second detection axis 123b. The sound component in the direction perpendicular to the first surface 101 is sound detected as a vibration component perpendicular to the first surface 101 in the vibration detection unit 120, that is, the detection signal of the first detection axis 123a. It is a sound detected as an in-phase component with the detection signal of the second detection axis 123b.

The components of the external sound 80 transmitted from the outside of the sound acquisition device 10 to the vibration detection unit 120 are absorbed by the housing 130 and transmitted to the vibration detection unit 120 via the support member 140, and are transmitted through the housing 130. And a transmission component 82 that is directly transmitted to the vibration detection unit 120.

As described in the embodiment and Example 1, the absorption component 81 becomes the sound component _{Sp1 in the} direction parallel to the first surface 101 in the support member 140, and adds the detection signal of the detection axis 123a and the detection signal of the detection axis 123b. Countered by matching. On the other hand, the transmitted component 82 is the sum of the sound component S _{v2 in the} direction perpendicular to the first surface 101 and the sound component S _{p2 in the} direction parallel to the first surface 101. Of the transmitted component 82 reaching the vibration detection unit 120, the sound component _{Sp2 in the} direction parallel to the first surface 101 is summed with the sound component _Sp1 by adding the detection signal of the detection shaft 123a and the detection signal of the detection shaft 123b. It will be canceled as well. On the other hand, the sound component _{Sv2 in the} direction perpendicular to the first surface 101 cannot be removed by simple signal addition.

Here, the sound source of the absorption component 81 and the transmission component 82 is common to the external sound 80. The absorption component 81 is expressed by “sound source” × “the transfer function of vibration of the casing 130”, and the transmission component 82 is expressed by “sound source” × “the transfer function of transmission of the casing 130”. Therefore, if the “transfer function of the vibration of the casing 130” is known, the “sound source” can be specified by back calculation. Furthermore, the transmission component 82 can be identified by multiplying the identified “sound source” by the “transmission transfer function of the casing 130”. This will be described in more detail below.

From the definition of each transfer function described above, S _pN = S _N × G ₁ and S _vN = S _N × G ₂ hold. Therefore, a relationship of S _vN = (G ₂ / G ₁ ) × S _pN is obtained. Note as described above, the absorbent component 81 since only contains the _{S _pN,} a _S _pN = S p1 ₊ S _p2 and _{_S} vN ₌ _S _v2.

The acquisition of the sound from the target portion 90, the vibration detection unit 120, a sound component S _p direction parallel to the first surface 101, a sound component S _v in a direction perpendicular to the first surface 101 can be detected separately . That is, the sound component S _p is obtained from the reverse phase component of the detection signal of the detection signal and the second detection axis 123b of the first detection axis 123a, a sound component S _v is a detection signal of the first detection axis 123a It is obtained from the same phase component as the detection signal of the second detection axis 123b. More specifically, the sound component S _p is obtained as a difference between the detection signal of the detection signal and the second detection axis 123b of the first detection axis 123a, a sound component S _v is the detection signal of the first detection axis 123a And the sum of the detection signal of the second detection shaft 123b.

Here, since the target sound S _o is included only in the sound component S _v , S _p = S _pN and S _v = S _vN + S _o . Therefore, So = S _v −S _vN = S _v − (G ₂ / G ₁ ) × S _p holds.

As described above, if the transfer functions G ₁ and the transfer function G ₂ is known, it can use the sound component obtained S _v and sound components S _p, extracts a target sound S _o. Specifically, from the sound component S _v, by subtracting the component multiplied by G _{2 /} G ₁ to the sound component S _p, it is possible to generate sound data with reduced noise by a transmission component 82.

Each transfer functions G ₁ and the transfer function G ₂ is dependent on the material and shape of the housing 130. The transfer function G ₁ and the transfer function G ₂ is can be obtained in advance in the following manner. First, a sound source is arranged outside the sound acquisition device 10, specifically, outside the housing 130 of the grip unit 100. Then, a known sound is generated from the sound source and detected by the vibration detection unit 120. At this time, the first surface 101 is pressed against a stationary rigid body so that no sound is input from the first surface 101. Further, as the detection result of the vibration detection unit 120, as described above, a sound component S _p direction parallel to the first surface 101, to derive respectively a direction of the sound component S _v parallel to the first surface 101 .

Transmitting from the relationship between known sound and sound component S _p from the sound source function G ₁ is obtained. Further, the transfer function G ₂ is obtained from the relationship between known sound and sound component S _v from the sound source. The resulting transfer function G ₁ and the transfer function G ₂ is allowed to hold in the storage unit 115, processing unit 110 can be used for processing by reading them.

The processing of the processing unit 110 according to this embodiment described above can also be expressed as follows. The plurality of detection axes 123 include a first detection axis 123a and a second detection axis 123b. Then, the processing unit 110 uses the detection signal of the first detection axis 123a and the second detection axis using the opposite phase components of the detection signal of the first detection axis 123a and the detection signal of the second detection axis 123b. Sound data is generated by processing the same phase component as the detection signal 123b.

In addition, according to the present embodiment, the processing unit 110 generates sound data using the first transfer function G ₁ , the second transfer function G ₂ , and the output from the vibration detection unit 120. Therefore, noise due to sound components transmitted through the housing 130 can be reduced, and sound data with fewer noise components can be generated.

Example 3
FIG. 10 is a cross-sectional view illustrating the structure of the sound acquisition device 10 according to the third embodiment. This figure corresponds to FIG. 6 of the first embodiment. The sound acquisition device 10 according to the present embodiment includes the first embodiment and the first embodiment except that a plane 146 that passes through a plurality of connecting portions of the support member 140 with respect to the housing 130 passes near the center of the plurality of sensor elements 122. 2 is the same as the sound acquisition device 10 according to at least one of the above. This will be described in detail below.

In this embodiment, the surface of the support member 140 on the side opposite to the diaphragm 150 of the base portion 142 is provided with a recess at the center as viewed from the direction perpendicular to the first surface 101. The convex portion 144 rises from the bottom of the concave portion. Further, the support member 140 is connected to the housing 130 outside the concave portion of the base portion 142. As a result, the plane 146 passing through the plurality of connecting portions of the support member 140 with respect to the casing 130 passes through the vicinity of the centers (intersections of dotted lines in the drawing) of the plurality of sensor elements 122. By doing so, the loss of the noise reduction effect can be minimized without being influenced by the angle θ formed by the two detection axes 123.

FIG. 11 is a diagram for explaining the relationship between the structure of the sound acquisition device 10 and the detection sensitivity of the absorption component 81. In this figure, the relationship between the housing 130, the support member 140, the sensor element 122a, and the sensor element 122b of the sound acquisition device 10 is illustrated. The noise absorption component 81 is transmitted from the connection portion between the housing 130 and the support member 140 and propagates toward the vibration detection unit 120, but the propagation is radial. At this time, the absorption component 81 is vector-decomposed in the direction of each sensitivity axis (detection axis 123) of the sensor element 122a and the sensor element 122b, and detected by each sensitivity axis of the sensor element 122. As a result, a difference occurs in the detection level.

More specifically, the difference between α and β described below appears as a difference in detection sensitivity with respect to the absorption component 81 of the sensor element 122a and the sensor element 122b. α is an angle formed by the straight line 125 and the straight line 127, and β is an angle formed by the straight line 126 and the straight line 127. Here, the straight line 125 passes through the center of the sensor element 122a and the center of the sensor element 122b and is perpendicular to the first surface 101, and the center of the sensor element 122a that is the sensor element 122 farthest from the connection part. Is a straight line connecting In the present embodiment, hereinafter, “a section perpendicular to the first surface 101 passing through the center of the sensor element 122a and the center of the sensor element 122b” is simply referred to as “a section perpendicular to the first surface 101”. The straight line 126 is a straight line that connects the connecting portion and the center of the sensor element 122 b that is the sensor element 122 closest to the connecting portion in a cross section perpendicular to the first surface 101. The straight line 127 is a straight line connecting the center of the sensor element 122a and the center of the sensor element 122b in a cross section perpendicular to the first surface 101. In the example of this figure, the connecting portion is the center of the convex portion for fitting the support member 140 and the housing 130 in a cross section perpendicular to the first surface 101.

Here, in the cross section perpendicular to the first surface 101, the distance between the connecting portions at both ends of the support member 140 is A, the distance between the plane 146 and the straight line 127 is H, the center of the sensor element 122a and the center of the sensor element 122b. Let L be the distance. Then, α = tan ⁻¹ (H / (A / 2 + L / 2)) × 180 / π holds, and β = tan ⁻¹ (H / (A / 2−L / 2)) × 180 / π holds.

The relationship between α and β is not particularly limited, but it is preferable that | α−β | <1 holds from the above viewpoint.

FIG. 12 is a diagram illustrating a modification of the support member 140 and the pressure sensor 152 of the sound acquisition device 10. FIG. 10 shows an example in which the pressure sensor 152 is provided between the surface of the support member 140 facing the diaphragm 150 and the diaphragm 150. However, in the example of this drawing, the pressure sensor 152 is the support member 140. It is provided only in a part of the area between the surface facing the diaphragm 150 and the diaphragm 150. The support member 140 is in direct contact with the diaphragm 150 in a partial region of the surface on the diaphragm 150 side. In addition, in the structure of FIG. 6 demonstrated in Example 1, such arrangement | positioning of the pressure sensor 152 may be employ | adopted.

In addition, according to the present embodiment, the planes 146 that pass through the plurality of fixed ends of the support member 140 with respect to the housing 130 pass through the vicinity of the centers of the plurality of sensor elements 122. Therefore, noise can be reduced more effectively by the processing of the processing unit 110.

(Example 4)
FIG. 13A to FIG. 13C are diagrams illustrating a plurality of detection axes 123 according to the fourth embodiment. These drawings show a state in which the plurality of detection axes 123 are viewed from a direction perpendicular to the first surface 101. The sound acquisition device 10 according to the present embodiment is the same as the sound acquisition device 10 according to at least one of the first to third embodiments, except that the plurality of detection axes 123 include a plurality of pairs. This will be described in detail below.

In this embodiment, each of the plurality of pairs is a pair of two detection axes 123 whose projections onto the first surface 101 are parallel to each other as described in the first embodiment.

FIG. 13A shows an example in which a plurality of detection axes 123 are composed of two pairs. In the example of this figure, the vibration detection unit 120 has four detection axes 123 whose directions are different by 90 degrees. In the case of the example of this figure, the convex part 144 may be a quadrangular pyramid shape, for example.

FIG. 13B shows an example in which a plurality of detection axes 123 are composed of three pairs. In the example of this figure, the vibration detection unit 120 has six detection axes 123 whose directions are different by 60 °. In the case of the example of this figure, the convex part 144 may be a hexagonal pyramid shape, for example.

FIG. 13C shows an example in which a plurality of detection axes 123 are composed of four pairs. In the example of this figure, the vibration detection unit 120 has eight detection axes 123 whose directions are different by 45 °. In the case of the example of this figure, the convex part 144 may be an octagonal pyramid shape, for example.

In the present embodiment, the processing unit 110 performs the processing described in the first or second embodiment for each pair, and obtains data for each pair. Then, the sound data is obtained by adding the obtained pairs of data. By doing so, data with reduced noise is obtained for each pair, and the target sound can be increased by adding them together. As a result, sound data with an improved S / N ratio can be obtained.

Note that the positional relationship between the plurality of detection axes 123 is not limited to the examples in FIGS. 13A to 13C. The plurality of detection axes 123 may include five or more pairs.

In addition, according to the present embodiment, the plurality of detection axes 123 include a plurality of pairs. Therefore, sound data with further improved S / N ratio based on the detection results of four or more detection axes 123 can be obtained.

As mentioned above, although embodiment and the Example were described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

This application claims priority based on Japanese Patent Application No. 2018-114213 filed on June 15, 2018, the entire disclosure of which is incorporated herein.

Claims

A vibration detecting unit including one or more sensor elements and having a plurality of detection axes;
A support member for supporting the vibration detection unit,
The sound acquisition device, wherein the plurality of detection axes are non-parallel to each other and are inclined with respect to a first surface facing the target portion.
The sound acquisition device according to claim 1,
A sound acquisition apparatus further comprising a processing unit that generates sound data by processing an output from the vibration detection unit.
The sound acquisition device according to claim 2,
The plurality of detection axes includes a pair of two detection axes whose projections on the first surface are parallel to each other.
The sound acquisition device according to claim 3,
A sound acquisition device in which the angles of the two detection axes constituting the pair with respect to the first surface are equal to each other.
The sound acquisition device according to claim 4,
The processing unit is a sound acquisition device that generates the sound data by adding detection signals for the two detection axes constituting the pair.
The sound acquisition device according to any one of claims 3 to 5,
The sound acquisition device in which an angle formed by the two detection axes constituting the pair is not less than 60 ° and not more than 120 °.
The sound acquisition device according to any one of claims 3 to 6,
The plurality of detection axes are sound acquisition devices including a plurality of the pairs.
The sound acquisition device according to any one of claims 2 to 7,
The vibration detection unit includes a plurality of the sensor elements,
The support member is provided with a support surface that supports each of the plurality of sensor elements,
The sound acquisition device, wherein the plurality of support surfaces are inclined with respect to the first surface and face different directions.
The sound acquisition device according to claim 8,
The support member has a base portion and a convex portion protruding from the base portion to the side opposite to the first surface side,
A sound acquisition device in which the support surface is provided on a side surface of the convex portion.
The sound acquisition device according to claim 9,
The sound acquisition device in which the outer peripheral portion of the base portion is physically connected to a housing of a grip portion that a user touches.
The sound acquisition device according to claim 10,
The processing unit generates the sound data using a first transfer function, a second transfer function, and an output from the vibration detection unit,
The first transfer function is a transfer function when an external sound of the sound acquisition device is input and a sound component in a direction parallel to the first surface in the vibration detection unit is output.
The second transfer function is a sound acquisition device that is a transfer function when a sound external to the sound acquisition device is input and a sound component in a direction perpendicular to the first surface of the vibration detection unit is output.
The sound acquisition device according to claim 10,
The plurality of detection axes include a first detection axis and a second detection axis,
The processing unit uses the opposite phase component of the detection signal of the first detection axis and the detection signal of the second detection axis to detect the detection signal of the first detection axis and the second detection axis. A sound acquisition device that generates the sound data by processing an in-phase component with a detection signal.
The sound acquisition device according to any one of claims 8 to 12,
The sound acquisition device, wherein the sensor element is an acceleration sensor.
The sound acquisition device according to any one of claims 2 to 13,
It further comprises a diaphragm for contacting or approaching the target part,
The sound acquisition device, wherein the first surface is a surface facing the target portion of the diaphragm.
The sound acquisition device according to claim 14,
A pressure sensor for detecting a pressure from the target portion to the diaphragm between the diaphragm and the support member;
The processing unit is a sound acquisition device that controls generation timing of the sound data using an output of the pressure sensor.
The sound acquisition device according to any one of claims 2 to 15,
The sound acquisition device is an electronic stethoscope,
A sound acquisition apparatus further comprising an output unit that outputs a sound based on the sound data.
The sound acquisition device according to any one of claims 1 to 16,
The target acquisition unit is a sound acquisition device that is a part of a living body.