Detection device

Abstract

This detection device for detecting vibration of a subject includes: a diaphragm displaced in accordance with the vibration of the subject; a generation unit that generates acoustic data representing a sound signal based on vibration transmitted from the subject via the diaphragm; a determination unit that determines the value of an adjustment parameter for adjusting a sound volume on the basis of a setting level of the sound volume of the detection device; and a change unit that changes the setting level in response to acquisition of an instruction for changing the sound volume from a user. The detection device can operate in a first mode for detecting vibration in a first frequency band and a second mode for detecting vibration in a second frequency band different from the first frequency band. For the same numerical setting level, the value of the adjustment parameter used when the detection device is in the first mode and the value of the adjustment parameter used when the detection device is in the second mode are different from each other.

Description

Detection device

[0001] The present disclosure relates to a detection device.

[0002] In recent years, electronic stethoscopes having sensors for measuring the vibrations of a living body and capable of acquiring body sounds by the sensors have begun to spread. Patent Document 1 describes a technique for setting the gain of an analog signal according to the operation of a plurality of gain buttons. Patent Document 2 describes a technique for selectively enhancing a frequency component corresponding to a heart sound and a frequency component corresponding to a breath sound.

[0003] Japanese Patent Application Laid-Open No. 2024-27215 Japanese Patent Application Laid-Open No. 2005-52521

[0004] Human auditory characteristics vary depending on the frequency of sound. Therefore, if the magnitude (volume) of a sound signal is uniformly changed regardless of the frequency band of the vibration to be detected, the change in volume (loudness) expected by the user may not be achieved. Some aspects of the present disclosure provide a technique for appropriately adjusting the magnitude of a sound signal.

[0005] According to some embodiments, there is provided a detection device for detecting vibrations of a subject, comprising: a diaphragm that is displaced in response to the vibrations of the subject; generation means for generating acoustic data representing a sound signal based on the vibrations transmitted from the subject through the diaphragm; determination means for determining a value of an adjustment parameter for adjusting the volume based on a set level of the volume of the detection device; and change means for changing the set level in response to obtaining an instruction to change the volume from a user. The detection device is operable in a first mode for detecting vibrations in a first frequency band and a second mode for detecting vibrations in a second frequency band different from the first frequency band, and for the same numerical set level, the value of the adjustment parameter used when the detection device is in the first mode and the value of the adjustment parameter used when the detection device is in the second mode are different from each other.

[0006] According to the above embodiment, the magnitude of the sound signal can be appropriately adjusted.

[0007] Other features and advantages of the technical ideas derived from this disclosure will become apparent from the following description with reference to the attached drawings. In the attached drawings, the same or similar components are given the same reference numeral.

[0008] The attached drawings are included in the specification and constitute part thereof, illustrating embodiments in this disclosure and used to explain the technical ideas derived from this disclosure together with their descriptions. Schematic diagram illustrating an example of the appearance of an electronic stethoscope in some embodiments. Schematic diagram illustrating an example of the configuration of a chestpiece in some embodiments. Schematic diagram illustrating an example of the operation of a chestpiece in some embodiments. Schematic diagram illustrating an example of the operation of a chestpiece in some embodiments. Schematic diagram illustrating an example of the movement of reflected light in some embodiments. Diagram illustrating the relationship between displacement and displacement signal in some embodiments. Block diagram illustrating an example of the circuit configuration of an electronic stethoscope in some embodiments. Block diagram illustrating an example of the functional configuration of an electronic stethoscope in some embodiments. Flowchart illustrating an example of a method for format conversion processing of an electronic stethoscope in some embodiments. Flowchart illustrating an example of a method for volume change processing of an electronic stethoscope in some embodiments. Diagram illustrating an example of parameters defining the volume of an electronic stethoscope in some embodiments. Diagram illustrating an example of equal-loudness curves in some embodiments. Diagram illustrating an example of sound signal processing of an electronic stethoscope in some embodiments.

[0009] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the scope of the claims. While the embodiments describe multiple features, not all of these features are necessary, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0010] In addition, the definitions of terms used herein are as follows: "Volume" means the sound pressure level or the output level based thereon measured by a sound output device under specified test conditions (e.g., an ear simulator compliant with IEC 60318-4, ambient temperature 25°C, relative humidity 50%, specified output path setting), unless otherwise specified. "Volume setting level (volume index)" means the discrete level of volume steps operated by the user. "Adjustment parameter" means a parameter applied to adjust the output of the sound signal according to the volume setting level (e.g., amplitude multiplier, offset, nonlinear mapping coefficient, digital volume code, analog gain setting). "Mode" means an operating mode with a different frequency band to be detected (e.g., heartbeat sound mode, respiratory sound mode). Also, unless otherwise specified, "acoustic data" is synonymous with audio data or sound data, and refers to the digital representation of a sound signal (e.g., PCM, encoded data).

[0011] [Appearance of the Electronic Auscultation Device] Referring to Figure 1, the appearance of the electronic auscultation device 100 according to some embodiments will be described. In Figure 1 and some subsequent drawings, a coordinate system CS, which is a three-dimensional Cartesian coordinate system having x, y, and z axes, is attached to indicate direction. Figure 1 shows the appearance of the electronic auscultation device 100 when viewed from a certain direction. The electronic auscultation device 100 is a medical device used by doctors, nurses, etc., as a diagnostic instrument to listen to the internal sounds of living organisms. The electronic auscultation device 100 is mainly used to listen to heart sounds and respiratory sounds. The electronic auscultation device 100 is an example of a detection device that detects vibrations of a subject. The electronic auscultation device 100 may be used, for example, for auscultation of a living organism, in which case the subject is a living organism. A living organism may be a human or an animal other than a human. The following description will focus on the case where the subject is a living organism, but the subject may be an object other than a living organism.

[0012] As shown in Figure 1, the electronic auscultation device 100 has a chestpiece 110 and a gripping part 120. During diagnosis, the chestpiece 110 is brought into contact with the surface of the body and measures minute vibrations (displacements) of the body surface to capture biological sounds. The chestpiece 110 detects minute displacements of the body surface in close contact with it via a diaphragm 206, which will be described later.

[0013] The gripping section 120 is used to grip the diaphragm 206 when the user of the electronic stethoscope 100 brings it into close contact with a biological surface. The gripping section 120 is rod-shaped, and a chestpiece 110 is attached to one end (the negative x-axis direction in Figure 1). The gripping section 120 has a housing 121, which houses a battery and a circuit board. Circuit elements for controlling the operation of the electronic stethoscope 100 are mounted on the circuit board. The gripping section 120 further includes a display section 122, an operation section 123, a power switch 124, and a connector 125.

[0014] The display unit 122 has multiple indicators, each of which displays the status of the electronic stethoscope 100. For example, these indicators indicate the power-on status, the current operating mode, the communication status with the computer, and whether the chestpiece 110 is pressed against the body surface.

[0015] The control unit 123 has a number of physical buttons for receiving settings for the electronic stethoscope 100, and accepts user operations through these buttons. Specifically, the control unit 123 includes a volume up button 123a and a volume down button 123b for adjusting the volume of the output sound, and a mode switching button 123c for switching the operating mode of the electronic stethoscope 100. The electronic stethoscope 100 can operate by switching between a number of operating modes, including heart sound mode, respiratory sound mode, and power saving mode. Heart sound mode is an operating mode for detecting (or auscultating) heart sounds. Respiratory sound mode is an operating mode for detecting (or auscultating) respiratory sounds. Power saving mode is an operating mode that consumes less power than heart sound mode and respiratory sound mode. The electronic stethoscope 100 also obtains instructions to start or stop recording by long-pressing the mode switching button 123c.

[0016] The power switch 124 is a switch that turns the power of the electronic stethoscope 100 on and off. The connector 125 is a connector for receiving a cable or connector of an external device. Power is supplied from the external device to the battery contained in the gripping part 120 through the connector 125.

[0017] [Cross-sectional configuration of the chestpiece of the electronic stethoscope] An example of the configuration of the chestpiece 110 will be described with reference to Figure 2. The upper part of Figure 2 shows a cross-sectional view of the chestpiece 110, and the lower part of Figure 2 shows a plan view of the chestpiece 110. In the plan view, only the light-emitting circuit board 203, light-receiving circuit board 205, diaphragm 206, and light-reflecting part 207 are shown in order to clarify the positional relationship of the components.

[0018] The chestpiece 110 includes a holding member 201, a light-emitting element 202, a light-emitting circuit board 203, a light-receiving element 204, a light-receiving circuit board 205, a diaphragm 206, a light-reflecting part 207, and a housing 208. The housing 208 houses the holding member 201, the light-emitting element 202, the light-emitting circuit board 203, the light-receiving element 204, the light-receiving circuit board 205, and the light-reflecting part 207. Since the holding member 201 has diaphragm portions 209 and 210 formed on it, the housing 208 also houses the diaphragm portions 209 and 210. The diaphragm 206, together with the housing 208, forms part of the exterior of the electronic stethoscope 100.

[0019] The light-emitting element 202 is a light source that emits light and is a light-emitting diode (LED). The power supplied to the light-emitting element 202 is supplied from an external power source (the battery of the gripping part 120) of the chestpiece 110. The light-emitting element 202 is mounted on a light-emitting circuit board 203. The light-emitting circuit board 203 is equipped with peripheral circuits for defining the amount of light emitted by the light-emitting element 202, and power terminals for receiving power from an external power source of the chestpiece 110.

[0020] The light-receiving element 204 generates an electrical signal based on the amount of light it receives, using power supplied from a battery housed inside the gripping section 120. The power supplied to the light-receiving element 204 is supplied from the battery in the gripping section 120. The light-receiving element 204 is, for example, a phototransistor or a complementary metal-oxide-semiconductor (CMOS) sensor. The light-receiving element 204 is mounted on a light-receiving circuit board 205. In addition to the light-receiving element 204, the light-receiving circuit board 205 is also equipped with peripheral circuits for reading signals from the light-receiving element 204, signal terminals for outputting signals to devices outside the chestpiece 110, and power terminals for receiving power from an external power source to the chestpiece 110.

[0021] The diaphragm 206 is held by a retaining member 201 and positioned to contact a biological surface. The diaphragm 206 has a contact surface 206a that contacts the biological surface and an inner surface 206b that is the opposite side of the contact surface 206a. The diaphragm 206 also has a fixed portion 206c that is fixed to the retaining member 201. The fixed portion 206c is located on the outer circumference of the diaphragm 206. The portion of the diaphragm 206 inside the fixed portion 206c is not fixed to the retaining member 201. Therefore, the diaphragm 206 undergoes elastic deformation upon receiving pressure from the object being measured that is in contact with the contact surface 206a. Specifically, the diaphragm 206 vibrates in the z-axis direction with the fixed portion 206c as a node. The inner surface 206b of the diaphragm 206 is provided with a light-reflecting portion 207, which will be described later. The diaphragm 206 is a laminate of glass epoxy resin, which is made by impregnating glass fibers with epoxy resin and then heat-curing it.

[0022] The light-reflecting portion 207 reflects light emitted from the light-emitting element 202. The light-reflecting portion 207 is bonded to the inner surface 206b of the diaphragm 206 and moves integrally with the diaphragm 206 in the z-axis direction in conjunction with the vibration of the diaphragm 206, which is in close contact with the biological surface. The light-reflecting portion 207 has a circular outer edge in the plan view. The light-reflecting portion 207 has a diameter of 15 mm to 20 mm and is positioned to cover the region 206d of the diaphragm 206 that includes the center 206e of the circle. Since the displacement of the diaphragm 206 changes most significantly at the center 206e, the displacement of the diaphragm 206 can be detected with high sensitivity by reflecting light from the light-emitting element 202 in the region including the center 206e. The light-reflecting portion 207 is made of, for example, an aluminum vapor-deposited film.

[0023] The light-emitting element 202 emits light toward the inner surface 206b of the diaphragm 206. The upper surface of the light-reflecting part 207 reflects the light emitted from the light-emitting element 202. That is, the upper surface of the light-reflecting part 207 functions as a light-reflecting surface. In the following description, the reflection of light at the upper surface (light-reflecting surface) of the light-reflecting part 207 will simply be referred to as "light being reflected by the light-reflecting part 207." The light-reflecting part 207 specularly reflects (in other words, mirror-reflects) the light emitted from the light-emitting element 202. In the following description, the light traveling from the light-emitting element 202 toward the light-reflecting part 207 will be referred to as incident light 211, and the light after the incident light 211 has been reflected will be referred to as reflected light 212.

[0024] The light-emitting element 202 is positioned to emit light toward a region 207a of the light-reflecting portion 207 that includes the portion covering the center 206e of the diaphragm 206, when the diaphragm 206 is not in contact with the biological surface. When the diaphragm 206 is not in contact with the biological surface, the diaphragm 206 is flat. The light-emitting element 202 emits light toward a specific region (for example, region 207a) of the light-reflecting portion 207. As described above, an LED that emits diffuse light is used as the light-emitting element 202. Therefore, the chestpiece 110 has a diaphragm portion 209 that narrows the light emitted from the light-emitting element 202. The diaphragm portion 209 ensures that only a portion of the light emitted from the light-emitting element 202 enters the light-reflecting portion 207. In the example in Figure 2, the portion of the holding member 201 with an opening corresponds to the diaphragm portion 209.

[0025] The light-receiving element 204 is positioned to receive reflected light 212. Specifically, the light-receiving element 204 is positioned so that the amount of reflected light 212 received changes due to the vibration of the diaphragm 206 in the z-axis direction. The light-receiving element 204 is positioned so that when the diaphragm 206 is not in contact with the biological surface (i.e., when the diaphragm 206 is flat), it receives more light in the reflected light 212 compared to when the diaphragm 206 is vibrating. That is, the light-receiving element 204 outputs an electrical signal corresponding to the amount of reflected light 212 it receives, and the amount of displacement of the diaphragm 206 can be determined based on this electrical signal. This principle will be described later. The chestpiece 110 has an aperture section 210 that narrows the light specularly reflected by the light-reflecting section 207. The aperture section 210 suppresses diffusely reflected light from entering the light-receiving element 204, and allows at least a portion of the light from the light-reflecting section 207 to reach the light-receiving element 204. In the example shown in Figure 2, the portion of the holding member 201 in which the opening is formed functions as the constricted portion 210.

[0026] A housing 208 is attached to the outer upper surface of the holding member 201. The housing 208 covers the light-emitting circuit board 203 and the light-receiving circuit board 205, and also suppresses ambient noise from entering the housing 208.

[0027] [Example of operation of the electronic stethoscope] An example of operation of the chestpiece 110 of the electronic stethoscope 100 will be described with reference to Figures 3A and 3B. As shown in Figures 3A and 3B, the chestpiece 110 is used in contact with the biological surface 300 to be measured. As a result, the biological surface 300, the diaphragm 206, and the light reflecting part 207 vibrate together. Therefore, the chestpiece 110 detects the displacement of the upper surface of the light reflecting part 207 in the z-axis direction as the displacement of the biological surface 300 in the z-axis direction. The displacement of the biological surface 300 occurs in response to bodily movements such as heartbeat and respiration of the person having the biological surface 300.

[0028] Figure 3A shows a cross-sectional view of the chestpiece 110 when the diaphragm 206 is flat. As described above, the light-emitting element 202 and the light-receiving element 204 are arranged so that when the diaphragm 206 is flat, more reflected light 212 is received by the light-receiving element 204 compared to when the diaphragm 206 is vibrating. The light-receiving element 204 amplifies and outputs a photocurrent corresponding to the amount of light it receives. The peripheral circuit of the light-receiving circuit board 205 generates an output value obtained by converting the photocurrent output from the light-receiving element 204 into a voltage, and outputs this displacement signal to an external device. The displacement signal refers to the output value of the light-receiving element 204 that reflects the state and deformation of the diaphragm 206 at any given time.

[0029] Figure 3B shows a cross-sectional view of the chestpiece 110 when the biological surface 300 is displaced upward. The distance between the light-emitting element 202 and the upper surface of the light-reflecting part 207 is represented by d1. When the biological surface 300 is displaced upward, the distance d1 decreases. Accordingly, the region 207a of the light-reflecting part 207 that the incident light 211 reaches moves closer to the light-emitting element 202, and the reflected light 212 also moves closer to the light-emitting element 202. As a result, the amount of reflected light 212 that reaches the photodetector 204 decreases, and the value of the displacement signal generated by the photodetector circuit board 205 becomes smaller. In the state shown in Figure 3B, since the reflected light 212 does not reach the photodetector 204 at all, the value of the displacement signal is ideally zero.

[0030] Thus, in the chestpiece 110, the light-emitting element 202 and the light-receiving element 204 are arranged such that the amount of light reaching the light-receiving element 204 changes in accordance with the movement of the biological surface 300, the diaphragm 206, and the light-reflecting part 207. Since the light-reflecting part 207 is displaced in conjunction with the displacement of the biological surface 300, the displacement signal generated by the light-receiving circuit board 205 represents the displacement of the biological surface 300.

[0031] [Relationship between diaphragm displacement and reflected light receiving position in electronic stethoscope] Referring to Figure 4, the relationship between the displacement of the biological surface 300, the incident angle of incident light 211, the incident angle of reflected light 212, and the displacement of the position where the light receiving element 204 receives the reflected light 212 will be explained. In Figure 4, position 401 indicates the reference position of the upper surface of the light reflecting part 207. The upper surface of the light reflecting part 207 when the diaphragm 206 is flat is taken as the reference position. Position 402 indicates the position where the upper surface of the light reflecting part 207 is displaced upward by a displacement amount d2 from position 401. Since the displacement amount d2 of the light reflecting part 207 is small, even when the upper surface of the light reflecting part 207 is at position 402, the upper surface of the light reflecting part 207 is considered to be flat.

[0032] In Figure 4, the optical axis 403 indicates the optical axis of the incident light 211. The angle of incidence of light emitted from the light-emitting element 202 and incident on the light-reflecting part 207 is represented by θ. The angle of incidence θ of the incident light 211 is determined by the angle between the optical axis 403 of the incident light 211 and the normal to the upper surface of the light-reflecting part 207. When the upper surface of the light-reflecting part 207 is at position 401, the optical axis of the reflected light 212 is defined as optical axis 404. When the upper surface of the light-reflecting part 207 is at position 402, the optical axis of the reflected light 212 is defined as optical axis 405. Since the incident light 211 is specularly reflected at the upper surface of the light-reflecting part 207, the angle of reflection of the reflected light 212 is also θ. Optical axes 404 and 405 are parallel to each other. Also, when the angle of incidence of the reflected light 212 to the photodetector 204 is φ, φ is 0°. When the upper surface of the light-reflecting portion 207 is displaced from position 401 to position 402, the displacement amount of the position where the light-receiving element 204 receives the reflected light 212 is denoted as d3. The displacement amount d3 may also be defined by the displacement amount from the position where the light-receiving element 204 receives light from the optical axis 404 to the position where the light-receiving element 204 receives light from the optical axis 405. In the following explanation, the ratio of the displacement amount d3 to the displacement amount d2 is denoted as the displacement magnification G. In this case, the relationship G = 2 × sinθ / cosφ …(Equation 1) holds. Therefore, even if the displacement amount d2 of the light-reflecting portion 207 is the same, the larger the incident angle θ, the larger the displacement magnification G, and the larger the incident angle φ, the larger the displacement magnification G.

[0033] Figure 4 illustrates the case where the incident angle φ is 0°. That is, the optical axes 404 and 405 are perpendicular to the light-receiving surface of the photodetector 204. In this case, equation 1 becomes G = 2 × sinθ …(equation 2). In other words, the larger the incident angle θ, the larger the displacement d3.

[0034] In the electronic stethoscope 100, as described above, an LED is used as the light-emitting element 202, and the displacement of the diaphragm 206 is measured based on the amount of light received by the light-receiving element 204. Alternatively, a laser beam may be used as the light-emitting element 202, and the displacement of the diaphragm 206 may be measured based on the position of the light received by the light-receiving element 204.

[0035] [Relationship between Displacement Amount and Displacement Signal of the Biological Surface of the Electronic Auscultation Device] The relationship between the displacement amount of the biological surface 300 and the displacement signal will be explained with reference to Figure 5. The displacement signal represents the voltage output from the light-receiving circuit board 205. Graph 500 in Figure 5 shows the relationship between the displacement amount of the biological surface 300 and the displacement signal. The horizontal axis of graph 500 represents the displacement amount of the biological surface 300 and represents the displacement signal generated by the light-receiving circuit board 205.

[0036] As described above, the displacement of the biological surface 300 is equal to the displacement d2 of the upper surface of the light reflecting part 207. As shown in Figures 3A and 3B, as the displacement d3 of the reflected light 212 increases, the amount of reflected light 212 that reaches the photodetector 204 decreases monotonically and linearly. Therefore, if we represent the value of the displacement signal as Sd, we get Sd = Vmax - k × d3 …(Equation 3). Here, Vmax is the value of the displacement signal when the displacement d3 of the reflected light 212 is zero, and k is a proportionality constant determined by the amplification factor of the amplification circuit of the photodetector circuit board 205. By substituting d3 = G × d2 and Equation 1 into Equation 3, we obtain Sd = Vmax - 2k × d2 × sinθ / cosφ …(Equation 4). Therefore, as shown in Graph 500, the displacement signal Sd decreases monotonically and linearly as the displacement d2 of the biological surface 300 increases. The displacement amount at which the displacement signal Sd becomes zero is denoted as dmax. When the displacement amount exceeds dmax, the reflected light 212 no longer reaches the photodetector 204, so even if the displacement amount d2 increases, the displacement signal Sd remains zero. Therefore, the proportionality constant k, the incident angle θ, and the incident angle φ are set so that the displacement amount d2 is in the range of 0 or more and dmax or less within the range in which the vibration of the diaphragm 206 is expected. As shown in graph 500, the light-emitting element 202 and the photodetector 204 are arranged so that the amount of light reaching the photodetector 204 changes monotonically in response to the movement of the light-reflecting part 207 in one direction within the operating range of the diaphragm 206.

[0037] In Equation 4, the coefficient of d2, 2k × sinθ / cosφ = k × G, represents the sensitivity of the chestpiece 110. The angle of incidence θ can take values ​​greater than 0° and less than 90°. The angle of incidence φ can take values ​​between 0° and less than 90°. The larger the displacement ratio G, the higher the sensitivity of the chestpiece 110. Therefore, the chestpiece 110 is configured such that the displacement ratio G is greater than 1, that is, the displacement amount d3 is greater than the displacement amount d2.

[0038] The chestpiece 110 can accurately detect the displacement of the biological surface 300. Specifically, in the chestpiece 110 described above, when the biological surface, which is an example of the object to be measured, is in close contact with the diaphragm 206, a displacement signal is generated based on the amount of displacement d2 of the biological surface that vibrates together with the diaphragm 206. Therefore, the displacement of the biological surface 300 can be accurately detected regardless of the frequency at which the biological surface 300 vibrates. For example, even displacement of the biological surface 300 due to low-frequency vibrations of about 10 Hz can be accurately detected. Such low-frequency vibrations are included in sounds (e.g., heartbeats) emitted by vibrations propagated from inside the body by the heartbeat. In the chestpiece 110, the displacement signal does not change unless the diaphragm 206 is displaced. Therefore, ambient noise and vibrations or accelerations due to the movement of the chestpiece 110 are not detected as noise, resulting in output characteristics with a high signal-to-noise ratio.

[0039] [Example of Circuit Configuration of Electronic Auscultation Device] An example of the circuit configuration of the electronic auscultation device 100 will be described with reference to Figure 6. The microcontroller 600 is a control means that controls the overall operation of the electronic auscultation device 100. In Figure 6, the electronic auscultation device 100 includes one microcontroller 600. Alternatively, the electronic auscultation device 100 may include multiple microcontrollers 600. The microcontroller 600 includes a processor 601, a non-volatile memory 602, a Bluetooth® circuit 603, and a RAM 604. The processor 601 controls the operation of the electronic auscultation device 100 by executing a program stored in the non-volatile memory 602. The non-volatile memory 602 is a storage device for storing a program that defines the operation of the electronic auscultation device 100 and various setting data, and maintains its contents even without external power supply. The Bluetooth circuit 603 is a control unit that controls a wireless communication unit 618 that conforms to the Bluetooth wireless communication standard. The wireless communication unit 618 includes an antenna for wireless communication. In Figure 6, the microcontroller 600 has a built-in Bluetooth circuit 603, but the Bluetooth circuit 603 may be located outside the microcontroller 600. The RAM 604 is a memory device that temporarily stores programs and various setting data read from the non-volatile memory 602.

[0040] The microcontroller 600 is implemented by multiple circuit elements mounted on a circuit board included in the gripping unit 120. The microcontroller 600 transmits an audio signal based on the displacement signal generated by the light-receiving element 204 to an external audio output device 670 via a wireless communication unit 618 or a wired communication unit 617. The audio output device 670 is, for example, a wired or wireless earphone or headphones. In addition to transmitting audio data to the audio output device 670, the microcontroller 600 can also transmit audio data to a computer 680 (for example, a personal computer, smartphone, tablet, etc.). The audio data represents sounds generated in the living body (i.e., biological sounds). Doctors, nurses, and public health nurses can listen to the biological sounds represented by the audio signals converted from the audio data using the audio output device 670 or the computer 680.

[0041] The displacement signal output from the light-receiving element 204 is filtered and amplified by the displacement signal processing unit 630 (described later) and supplied to the A / D converter 605. The A / D converter 605 digitizes the output from the displacement signal processing unit 630. The digital displacement signal is then converted by the microcontroller 600 to, for example, the Pulse Code Modulation (PCM) format, and then processed by an encoder, such as data compression and encoding, according to the communication standard, to be converted into acoustic data for wireless communication. The wireless communication unit 618 then transmits the acoustic data to the sound output device 670. The sound output device 670, upon receiving the acoustic data, outputs a sound corresponding to that acoustic data.

[0042] Incidentally, although the above-described electronic stethoscope device 100 has been described as an example capable of transmitting acoustic data by both wireless communication and wired communication, it may be possible to transmit acoustic data by only one of these communications. The transmission of acoustic data to the computer 680 is the same as the transmission of acoustic data to the sound output device 670. The computer 680 can also visually display the waveform data generated based on the received acoustic data. The waveform data may be generated by the computer 680 or may be generated by the electronic stethoscope device 100. Also, part or all of the signal processing and sound output processing by the electronic stethoscope device 100 may be performed by an external device (for example, the sound output device 670 or the computer 680).

[0043] The UART integrated circuit 620 is connected to each of the microcontroller 600 and the connector 125 (specifically, its data terminal). The UART integrated circuit 620 performs communication conforming to UART. The UART integrated circuit 620 and the connector 125 function as the wired communication unit 617. The microcontroller 600 may be able to communicate with an external device by wire through the UART integrated circuit 620 and the connector 125. The UART integrated circuit 620 may also be connected to the power terminal of the connector 125. A voltage VBUS may be applied to the UART integrated circuit 620 from an external device (for example, a charger or the computer 680) connected to the connector 125 through the power terminal of the connector 125. The UART integrated circuit 620 may be operable with the voltage VBUS as an operating voltage.

[0044] The power supply unit 610 includes a battery 611, a charging integrated circuit 612, a boost converter 613, a voltage regulator 614, a load switch 615, and a voltage regulator 616. The power supply unit 610 supplies power to a plurality of circuit elements included in the electronic stethoscope device 100. The power supply unit 610 may supply power at a plurality of different voltages. Instead of this, the power supply unit 610 may supply power at one voltage, and the voltage may be dropped so as to be an appropriate operating voltage in front of each circuit element.

[0045] The battery 611 stores the electrical energy used by the electronic stethoscope 100. The battery 611 may have a function to cut off the current flowing through it if it exceeds a threshold. The charging integrated circuit 612 is an integrated circuit (IC) that controls the charging of the battery 611 and the discharging of the battery 611. For example, the charging integrated circuit 612 charges the battery 611 using electrical energy supplied from an external device such as a charger or computer 680 connected to the connector 125. The charging integrated circuit 612 also supplies the electrical energy stored in the battery 611 to the boost converter 613. The voltage provided by the charging integrated circuit 612 is denoted as voltage VBAT. Voltage VBAT is, for example, 3.7V.

[0046] The boost converter 613 boosts a DC voltage to a DC voltage of another value. The boost converter 613 is also called a DC / DC converter. The boost converter 613 boosts the voltage VBAT supplied from the charging integrated circuit 612 to voltage V0. Voltage V0 is, for example, 6.8V. The voltage regulator 614 generates and outputs a voltage of a specific value. The voltage regulator 614 may be a linear regulator, also called a low-dropout regulator (LDO). The voltage regulator 614 generates the operating voltage for some circuit elements of the electronic stethoscope 100. The voltage generated by the voltage regulator 614 is denoted as voltage V1. The voltage regulator 614 may also generate the operating voltage for the microcontroller 600, for example, voltage V1 is 3.3V. The operating voltage of the accelerometer 650 is also voltage V1. In the example in Figure 6, voltage V1 is applied to the microcontroller 600 and the accelerometer 650, respectively. The microcontroller 600 and the acceleration sensor 650 are powered by the voltage regulator 614 of the power supply unit 610. The voltage regulator 614 outputs voltage V1 when a voltage higher than voltage V1 is applied to its input terminal. Therefore, the voltage regulator 614 outputs voltage V1 when voltage V0 is supplied from the boost converter 613.

[0047] The load switch 615 is a switch that switches between on (conductive state) and off (non-conductive state) in response to a control signal from the microcontroller 600. The voltage regulator 616 generates and outputs a voltage of a specific value. The voltage regulator 616 may be a linear regulator or a LDO. The voltage regulator 616 generates the operating voltage of some circuit elements of the electronic stethoscope 100. The voltage generated by the voltage regulator 616 is represented as voltage V2. The voltage regulator 616 may generate the operating voltage of the light emitting element 202 and the light receiving element 204. For example, the voltage V2 is 5.8V. In the example of FIG. 6, the voltage V2 is applied to each of the light emitting element 202 and the light receiving element 204. Power is supplied from the voltage regulator 616 of the power supply unit 610 to the light emitting element 202 and the light receiving element 204. The voltage regulator 616 outputs the voltage V2 when a voltage higher than the voltage V2 is applied to its input terminal. Therefore, the voltage regulator 616 outputs the voltage V2 when the load switch 615 is on. The voltage regulator 616 does not output the voltage V2 when the load switch 615 is off. The potential of the output terminal of the voltage regulator 616 when it does not output the voltage V2 is the ground potential.

[0048] The displacement signal processing unit 630 processes the diaphragm displacement signal to generate an audio signal based on vibrations transmitted from the biological surface through the diaphragm 206, and outputs this audio signal to the microcontroller 600. Specifically, the displacement signal processing unit 630 extracts components of a specific frequency band included in the diaphragm displacement signal and generates an audio signal. As will be described later, the extracted components of a specific frequency band include components in the frequency band range from 10 Hz to 1 kHz. The diaphragm displacement signal is a signal generated and output by the photodetector 204 in accordance with the amount of light that reaches the photodetector 204. Hereinafter, the diaphragm displacement signal will simply be referred to as the displacement signal. The amount of light that reaches the photodetector 204 changes in accordance with the displacement of the diaphragm 206. Note that, as described above, if the light-emitting element 202 is a laser diode that emits laser light, the displacement signal may also refer to a signal generated and output by the photodetector 204 in accordance with the position of the light that reaches the photodetector 204. Even when implemented with a laser diode, the displacement signal still represents the displacement of the diaphragm 206. The heartbeat sound signal is also a type of displacement signal because it represents the displacement of the diaphragm 206 (specifically, its components in a particular frequency band).

[0049] The displacement signal processing unit 630 includes a buffer circuit 631, a high-pass filter (HPF) 632, and amplifier circuits 633 and 634 with low-pass filters on the signal path between the photodetector 204 and the microcontroller 600. These circuit elements are connected in series. The displacement signal processing unit 630 receives a displacement signal from the photodetector 204 and outputs an audio signal to the microcontroller 600.

[0050] The buffer circuit 631 receives a displacement signal from the photodetector 204 and outputs the displacement signal to the HPF 632. The buffer circuit 631 performs impedance conversion of the signal path between the photodetector 204 and the HPF 632. For example, the output impedance of the buffer circuit 631 is lower than the output impedance of the photodetector 204. The operating power of the buffer circuit 631 is supplied by the voltage regulator 616.

[0051] The HPF 632 outputs a signal to the amplifier 633 obtained by attenuating the low-frequency components (i.e., frequency components lower than a specific cutoff frequency) of the displacement signal received from the buffer circuit 631 and passing the high-frequency components (i.e., frequency components higher than the said cutoff frequency) of the displacement signal. The cutoff frequency of the HPF 632 is set, for example, in the range of 10 to 20 Hz, and components below at least 10 Hz are removed or attenuated. The cutoff frequency is selected considering the need to ensure the dynamic range of the front end in heart rate mode and respiratory sound mode and to suppress DC component fluctuations.

[0052] The HPF632 is placed on the signal path between the photodetector 204 and the microcontroller 600 to remove or attenuate low-frequency noise contained in the displacement signal. The low-frequency noise contained in the displacement signal is a component that does not originate from vibrations transmitted from the biological surface to the diaphragm 206. For example, the low-frequency noise may include changes in the DC component due to the user's hand tremor of the electronic stethoscope 100, changes in the posture of the device, or the diaphragm 206 being pressed against the biological surface. Since these have a much larger amplitude than the biological components, the biological components can be appropriately acquired within the dynamic range of the amplification circuit by amplifying the displacement signal from which the low-frequency noise has been suppressed. As an alternative to the HPF632, an embodiment is also included in which a bandpass filter that attenuates components below at least 10 Hz is used.

[0053] [Example of Functional Configuration of an Electronic Auscultation Device] Referring to Figure 7, the functional blocks implemented by the processor 601 of the microcontroller 600 will be described. Each functional block in Figure 7 is implemented by the processor 601 loading a program stored in the non-volatile memory 602 into the RAM 604 and executing it. However, some or all of the functional blocks in Figure 7 may be implemented by a dedicated integrated circuit such as an application-specific integrated circuit (ASIC).

[0054] The motion detection unit 701 detects the movement of the electronic stethoscope 100 based on the acceleration signal acquired from the acceleration sensor 650. For example, the motion detection unit 701 determines that the electronic stethoscope 100 is moving if the acceleration in at least one of the three axes (x, y, and z) is not zero or exceeds a threshold. Conversely, the motion detection unit 701 determines that the electronic stethoscope 100 is stationary if the acceleration in all axes is zero or below a threshold.

[0055] The display control unit 702 controls the display of the display unit 122. The input acquisition unit 703 acquires user input using the operation unit 123 and the power switch 124. The power management unit 704 controls the operation of the power supply unit 610, for example, the operation of generating a specific voltage. Specifically, the power management unit 704 switches the level of the control signal supplied to the load switch 615, and switches the load switch 615 on and off. As described above, when the load switch 615 is turned off, voltage V0 is no longer supplied to the voltage regulator 616, so the power supply from the voltage regulator 616 is stopped, and the system switches to power saving mode.

[0056] The pressure detection unit 705 detects that the biological surface 300 is pressing against the diaphragm 206 based on the displacement signal acquired from the displacement signal processing unit 630. When the diaphragm 206 and the biological surface 300 come into contact with each other, the biological surface 300 presses against the diaphragm 206. Therefore, by detecting the pressure on the diaphragm 206 by the biological surface 300, contact between the diaphragm 206 and the biological surface 300 is detected. Hereinafter, the pressing state of the diaphragm 206 will be simply referred to as the pressing state. For example, the pressure detection unit 705 can identify which of several states the pressing state is. Specifically, the pressure detection unit 705 can identify whether the pressing state is in use or not. The not-use state is the pressing state when the user is not pressing the diaphragm 206 against the biological surface. The use state is the pressing state when the user is pressing the diaphragm 206 against the biological surface. The displacement of the diaphragm 206 in the non-use state is smaller than the displacement of the diaphragm 206 in the use state. Therefore, the pressure detection unit 705 determines that the pressing state is the non-use state when the displacement of the diaphragm 206 identified from the displacement signal is less than a threshold. On the other hand, the pressure detection unit 705 determines that the pressing state is the use state when the displacement of the diaphragm 206 exceeds the threshold.

[0057] Furthermore, the usage state is subdivided into two states: proper state and overpressure state. In this case, the pressure detection unit 705 identifies which of the three states the pressing state is: proper state, unused state, or overpressure state. An overpressure state is a pressing state in which the pressing force of the diaphragm 206 against the biological surface is too strong, and sound is not properly transmitted from the biological surface to the diaphragm 206. A proper state is a pressing state in which sound is properly transmitted from the biological surface to the diaphragm 206. The amount of displacement of the diaphragm 206 in an overpressure state is greater than the amount of displacement of the diaphragm 206 in a proper state. The pressure detection unit 705 determines that the pressing state is an unused state if the amount of displacement of the diaphragm 206 is less than a threshold. On the other hand, the pressure detection unit 705 determines that the pressing state is a proper state if the amount of displacement of the diaphragm 206 exceeds the threshold and is less than another threshold that is greater than the threshold. The pressure detection unit 705 determines that the pressing state is an overpressure state if the amount of displacement of the diaphragm 206 exceeds another threshold. The output control unit 706 transmits the sound signal acquired from the displacement signal processing unit 630 to an external device such as a computer 680 or a sound output device 670 via the wireless communication unit 618 or the wired communication unit 617. The output control unit 706 configures the electronic stethoscope 100 based on whether it is in heartbeat sound mode or respiratory sound mode. For example, the output control unit 706 configures at least one of the following based on whether the electronic stethoscope 100 is in heartbeat sound mode or respiratory sound mode: the sensitivity of the light receiving element 204, the cutoff frequency of the HPF 632, and the amplification factor of the amplification circuits 633 and 634. The sound signal output from the output control unit 706 when the electronic stethoscope 100 is in heartbeat sound mode is referred to as the heartbeat sound signal. The sound signal output from the output control unit 706 when the electronic stethoscope 100 is in respiratory sound mode is referred to as the respiratory sound signal.

[0058] The output control unit 706 performs signal processing on the sound signal before outputting it. Specifically, the output control unit 706 includes a volume adjustment unit 711 and a format conversion unit 712. The volume adjustment unit 711 applies adjustment parameters (e.g., amplitude magnification Mv, etc.) according to the volume index, taking into account the sound pressure level based on predetermined test conditions (e.g., ear simulator compliant with IEC 60318-4, ambient temperature 25°C, standard headphone output path) or the matching of subjective volume based on equal loudness curves (ISO 226). Details of the processing of the format conversion unit 712 will be described later.

[0059] The volume control unit 711 adjusts the volume of the sound signal (heartbeat sound signal or respiratory sound signal) output to the outside. Hereinafter, the volume of the sound signal output to the outside may be simply referred to as volume. For example, the volume control unit 711 adjusts the volume based on user input acquired by the input acquisition unit 703. For example, the volume control unit 711 increases the volume when the volume up button 123a included in the operation unit 123 of Figure 1 is operated by the user and instructs them to increase the volume. The volume control unit 711 decreases the volume when the volume down button 123b included in the operation unit 123 of Figure 1 is operated by the user and instructs them to decrease the volume.

[0060] The volume control unit 711 also automatically switches the volume based on the pressing state. Specifically, when the diaphragm 206 is pressed above a certain level by the object being measured (when it is determined to be in use), the volume is set to the normal level. The normal level volume is a volume suitable for listening to the sound signal reproduced by the sound output device 670. In the automatic switching based on the pressing state, a hysteresis width Δ is added to the threshold Th1 for determining the use state based on the displacement amount output by the pressing detection unit 705, with Th1+Δ used for upward determination and Th1-Δ used for downward determination. In addition, to prevent chattering, the state transition is only executed if it is detected continuously for a predetermined time (Tdebounce, for example, 50 to 200 ms) or longer. The volume control unit 711 adjusts the normal level value based on the user input acquired by the input acquisition unit 703.

[0061] The volume control unit 711 sets the volume to the mute level when the diaphragm 206 is not being pressed by the object being measured (i.e., it is determined to be in an unused state). The mute level means a volume that is zero or lower than the normal level, and may be so low that it is not suitable for hearing the sound signal reproduced by the sound output device 670. The mute level can be a constant multiple of the normal level (e.g., 10%) or it can be set independently of the normal level. In the former case, if the normal level changes due to user input via the volume control buttons included in the operation unit 123, the mute level also changes depending on the normal level. In the latter case, even if the normal level changes due to user input, the mute level does not change. Furthermore, a hysteresis width Δ is also applied to the unused state determination, and the rise / fall determination is performed with Th1±Δ, and the switch to / release of the mute level is performed only when the time threshold Tdebounce (e.g., 50-200ms) for preventing chattering is met. When the pressing state is excessive, it is not always necessary to set the volume to the mute level; the volume adjustment unit 711 may set the volume to the normal level, just as when the pressing state is appropriate.

[0062] The volume control unit 711 adjusts the volume level of the sound signal by adjusting the gain of at least one of the amplification circuits 633 and 634. Alternatively, the volume control unit 711 may adjust the sound signal output to the outside by the output control unit 706. When automatically switching between normal level and mute level based on the pressing state, the state transition is performed according to the hysteresis width Δ and time threshold Tdebounce described above, and if necessary, a fade process (e.g., linear / exponential fade of tens to hundreds of milliseconds) is applied to smooth the transient response when the gain is changed, thereby suppressing the generation of pop noise.

[0063] [Method for Outputting Sound Signals] A method for outputting sound signals will be described with reference to Figure 8. Each step of the method in Figure 8 is implemented by the processor 601 executing a program stored in the non-volatile memory 602. However, some or all of the steps of the method in Figure 8 may be implemented by a dedicated integrated circuit. The processor 601 starts the method in Figure 8 when the power to the electronic stethoscope 100 is turned on, and ends the method in Figure 8 when the power to the electronic stethoscope 100 is turned off. Alternatively, the processor 601 may start the method in Figure 8 when the electronic stethoscope 100 transitions from power-saving mode to another mode (for example, heart sound mode or respiratory sound mode). The processor 601 may also end the method in Figure 8 when the electronic stethoscope 100 transitions to power-saving mode.

[0064] In step S801, the processor 601 (for example, the format conversion unit 712; the same applies to the process in Figure 8 below) acquires the sound signal output from the displacement signal processing unit 630. As described above, the displacement signal processing unit 630 generates a sound signal based on the displacement signal generated by the light-receiving element 204. This sound signal represents the vibration of the diaphragm 206, and specifically represents the sound transmitted from the biological surface 300 to the diaphragm 206. The A / D converter 605 of the processor 601 digitizes the signal value of the sound signal. For example, the A / D converter 605 converts the signal value into a 12-bit digital value. In this case, the signal value of the sound signal is converted to any value in the range of 0 to 4095. Note that the number of quantization bits of the A / D converter 605 may be set to another number of bits (e.g., 16 bits).

[0065] In step S802, the processor 601 converts the sound signal acquired in S801 into a predetermined format. For example, the processor 601 converts the sound signal into PCM format. Assuming that the converted sound signal is represented by a signed integer and has 16 quantization bits, the sound signal is converted into a signal value in the range of -32768 to 32767. The converted sound signal represents the sound pressure level when this sound signal is played back. The data represented by the converted sound signal is called acoustic data. In this way, the processor 601 generates acoustic data representing the sound transmitted from the biological surface 300 through the diaphragm 206 based on the sound signal acquired in S801.

[0066] If S is the signal value of the audio signal to be converted, and S' is the signal value of the converted audio signal, then S' is calculated using the following equation 5 with a reference value B and a multiplier Mv: S' = (S - B) × 16 × Mv … (Equation 5)

[0067] Reference value B is a digital value that represents the state of silence (reference voltage) of the sound signal to be converted. For example, suppose the analog sound signal supplied to the microcontroller 600 takes a voltage in the range of 0V to 3.3V, and the reference voltage of the sound signal is 1.65V. The A / D converter 605 converts the voltages of 0V, 1.65V, and 3.3V into digital values ​​of 0, 2047, and 4095, respectively. In this case, the reference value B of the digital sound signal is 2047. In equation 5, "S - B" represents the amplitude of the sound signal to be converted.

[0068] The magnification Mv is an example of an adjustment parameter for adjusting the volume of the electronic stethoscope 100. In this specification, volume refers to the concept of loudness. Volume may mean objective loudness (e.g., sound pressure level) or subjective loudness (e.g., loudness). Generally, objective loudness and subjective loudness have a positive correlation. As an adjustment parameter for adjusting the volume of the electronic stethoscope 100, a value added to the amplitude of the sound signal may be used instead of or in addition to the magnification Mv.

[0069] As shown in Equation 5, the signal value S is adjusted (in other words, scaled) using a magnification factor Mv. Specifically, the magnification factor Mv is multiplied by the amplitude of the sound signal (S - B). The application of the magnification factor Mv may be in the digital domain (digital volume after PCM conversion), in digital processing before D / A conversion, or in the analog domain (gain setting of the amplification circuit). The method for determining the magnification factor Mv will be described later. The "16" in Equation 5 is a coefficient for adjusting the number of quantization bits of the sound signal to be converted (12 bits) and the number of quantization bits of the sound signal after conversion (16 bits).

[0070] In S803, the processor 601 outputs the audio data generated in S802 to an external device via the Bluetooth circuit 603. For example, the processor 601 transmits the audio data to an external device. In S804, the processor 601 waits for a predetermined time. The predetermined time is the sample period corresponding to the sampling rate used for output, for example, approximately 22.7 microseconds for 44.1 kHz and approximately 62.5 microseconds for 16 kHz. The format of the audio data during testing / output is, for example, quantized with 16-bit PCM (signed integer), and the sampling rate is 16 kHz or 44.1 kHz. This also includes configurations using other rates (e.g., 8 to 48 kHz) or codecs (e.g., LC3) as needed.

[0071] Subsequently, the processor 601 transitions to processing S801. In this way, the operations S801 to S804 are repeated at a predetermined cycle. In the method shown in Figure 8, sound data is transmitted to the external device each time it is generated. Alternatively, the processor 601 may combine the sound data into an audio file and transmit this audio file to the external device. The format of the audio file may be, for example, uncompressed WAV format, lossless compressed FLAC format, or lossy compressed mp3 format.

[0072] [Method for Changing Volume] Referring to Figure 9, a method for changing the volume of the sound signal output to an external device in response to instructions from the user of the electronic stethoscope 100 will be described. Each step of the method in Figure 9 is implemented by the processor 601 executing a program stored in the non-volatile memory 602. However, some or all of the steps of the method in Figure 9 may be implemented by a dedicated integrated circuit. The processor 601 starts the method in Figure 9 when the power to the electronic stethoscope 100 is turned on, and ends the method in Figure 9 when the power to the electronic stethoscope 100 is turned off. Alternatively, the processor 601 may start the method in Figure 9 when the electronic stethoscope 100 transitions from power-saving mode to another mode (for example, heart sound mode or respiratory sound mode). The processor 601 may also end the method in Figure 9 when the electronic stethoscope 100 transitions to power-saving mode.

[0073] In S901, the processor 601 (for example, the volume control unit 711) determines whether it has received an instruction from the user to increase the volume. If the processor 601 determines that it has received an instruction to increase the volume (YES in S901), it proceeds to S902; otherwise (NO in S901), it proceeds to S903. The processor 601 determines that it has received an instruction to increase the volume in response to the volume up button 123a being pressed.

[0074] In S902, the processor 601 (for example, the volume control unit 711) increments the volume index. The volume index is an integer representing the current set level of the volume of the electronic stethoscope 100. In the following description, the volume index can take six values ​​from "-3" to "2". The initial value of the volume index is, for example, "0". If the volume index is already at its maximum value, the processor 601 maintains the volume index at its maximum value.

[0075] In S903, the processor 601 (for example, the volume control unit 711) determines whether it has received an instruction from the user to lower the volume. If the processor 601 determines that it has received an instruction to lower the volume (YES in S903), it proceeds to S904; otherwise (NO in S903), it proceeds to S901. The processor 601 determines that it has received an instruction to lower the volume in response to the volume down button 123b being pressed.

[0076] In S904, the processor 601 (for example, the volume control unit 711) decrements the volume index. If the volume index is already at its minimum value, the processor 601 maintains the volume index at its minimum value. In this way, in S901 to S904, the processor 601 changes the volume index, which represents the current set level of the volume, in response to receiving an instruction from the user of the electronic stethoscope 100 to change the volume of the electronic stethoscope 100.

[0077] In S905, the processor 601 determines the multiplier Mv based on the current volume index. The processor 601 stores the determined multiplier Mv in the RAM 604 as the multiplier Mv to be used in subsequent processing. After that, the processor 601 transitions to processing S901. The multiplier Mv stored in the RAM 604 is used in S802 in Figure 8 above.

[0078] Specifically, the processor 601 determines the magnification Mv by referring to the correspondence table 1000 in Figure 10. As shown in the correspondence table 1000, the value of the magnification Mv corresponding to the same numerical volume index differs depending on whether the electronic stethoscope 100 is in heart sound mode or respiratory sound mode. For example, when the electronic stethoscope 100 is in heart sound mode and the volume index is "0", the magnification Mv is "0.16", and when the electronic stethoscope 100 is in respiratory sound mode and the volume index is "0", the magnification Mv is "0.1". Thus, although the volume index is "0" in both cases, the values ​​of the magnification Mv are different.

[0079] Referring to Figure 11, we will explain sound pressure level (objective loudness) and loudness (subjective loudness). Loudness can differ depending on the frequency of the sound, even for sounds with the same sound pressure level. Figure 11 shows a graph (equal loudness curves) with frequency on the horizontal axis and sound pressure level on the vertical axis, connecting identical loudness values ​​in increments of 10 phons from 10 phons to 130 phons. A phon is a unit of loudness. The value expressed in phons corresponds to the sound pressure level when the frequency is 1 kHz. Figure 11 also shows a graph showing the sound pressure level of the minimum audible sound at each frequency. The equal loudness curves conform to ISO 226.

[0080] In correspondence table 1000, for both the heart rate sound mode and the respiratory sound mode, the magnification Mv is specified so that when the volume index is "-1" to "2", the loudness is "10 phons" to "40 phons". In other words, the magnification Mv is specified so that the loudness changes at equal intervals as the volume index changes. Also in correspondence table 1000, for both the heart rate sound mode and the respiratory sound mode, the magnification Mv is specified so that when the volume index is "-3" and "-2", the loudness is "silent" and "minimum audible sound", respectively.

[0081] The values ​​of the magnification Mv in correspondence table 1000 are determined as follows. First, the magnification Mv when the volume is at its maximum (i.e., the volume index is "2") is set to 1, and the magnification Mv when the volume is at its minimum (i.e., the volume index is "-3") is set to 0. Then, the magnification Mv when the loudness is n phons is calculated according to the following formula 6: Mv = 1 ÷ (10 （Ａ－Ｂ）／２０ )...(Formula 6)

[0082] In Equation 6, A is the sound pressure level (dB SPL) at which the loudness at the target frequency is 40 phons. In Equation 6, B is the sound pressure level (dB SPL) at which the loudness at the target frequency is n phons. The target frequency and sound pressure level are obtained based on the equal-loudness contours of ISO 226.

[0083] The frequency of heartbeat sounds generally falls within the range of 30 Hz to 300 Hz. Therefore, when the electronic stethoscope 100 is in heartbeat sound mode, vibrations in the frequency band (first frequency band) that includes frequencies within the range of 30 Hz to 300 Hz are detected. Thus, when the electronic stethoscope 100 is in heartbeat sound mode, the magnification Mv is calculated by setting the target frequency in Equation 6 to, for example, 100 Hz. Referring to the equal loudness curves in Figure 11, when the target frequency is 100 Hz, the sound pressure levels at which the loudness is 40 phons, 30 phons, 20 phons, 10 phons, and the minimum audible sound are 52 dB, 44 dB, 36 dB, 29 dB, and 25 dB, respectively. Therefore, by substituting A = 52 and B = 44 into Equation 6, Mv ≈ 0.4 is calculated.

[0084] The frequencies of respiratory sounds generally fall within the range of 500 Hz to 2 kHz. Therefore, when the electronic stethoscope 100 is in respiratory sound mode, vibrations in a frequency band (second frequency band) that includes frequencies within the range of 500 Hz to 2 kHz are detected. Thus, when the electronic stethoscope 100 is in respiratory sound mode, the magnification Mv is calculated by setting the target frequency in Equation 6 to, for example, 1 kHz.

[0085] The processor 601 independently changes the volume index, which represents the volume setting level for the heart sound mode and the respiratory sound mode. For example, suppose the current volume index for both the heart sound mode and the respiratory sound mode is "0". Suppose the electronic stethoscope 100 is instructed to increase the volume while in heart sound mode. In this case, the processor 601 may increment the volume index for the heart sound mode to "1" and maintain the volume index for the respiratory sound mode at "0". On the other hand, suppose the electronic stethoscope 100 is instructed to increase the volume while in respiratory sound mode. In this case, the processor 601 may increment the volume index for the respiratory sound mode to "1" and maintain the volume index for the heart sound mode at "0". Similarly, if the volume is instructed to decrease, the volume index for only one of the modes is decremented. To perform this processing, the processor 601 stores the current volume index for the heart sound mode and the respiratory sound mode separately in the RAM 604. This process allows users to set their preferred volume for each mode.

[0086] Alternatively, the processor 601 may synchronously change the volume index representing the volume setting level for the heart sound mode and the respiratory sound mode. For example, suppose the current volume index for both the heart sound mode and the respiratory sound mode is "0". Suppose the electronic stethoscope 100 is in heart sound mode and the user is instructed to increase the volume. In this case, the processor 601 increments the volume index for both the heart sound mode and the respiratory sound mode to "1". Similarly, if the user is instructed to decrease the volume, the volume index for both modes is decremented. To perform this operation, the processor 601 stores the current single volume index for both the heart sound mode and the respiratory sound mode in the RAM 604. Alternatively, the current volume index for each of the heart sound mode and the respiratory sound mode may be stored separately in the RAM 604, and a change in one may result in the other being changed as well. This operation allows the user to set their preferred volume for the entire electronic stethoscope 100, regardless of the mode.

[0087] [Specific Examples of Magnification Determination and Sound Signal Conversion] Referring to Figure 12, specific examples of magnification Mv determination and sound signal conversion will be described. Graph 1201 shows the waveform of the displacement signal supplied to the microcontroller 600. The horizontal axis of graph 1201 represents time, and the vertical axis of graph 1201 represents voltage. The threshold Th1 is the voltage used to determine whether the diaphragm 206 is being pressed by the biological surface 300 (in other words, whether the diaphragm 206 and the biological surface 300 are in contact with each other).

[0088] Graph 1202 shows the waveform of the sound signal acquired in S801 of Figure 8. The horizontal axis of Graph 1202 represents time, and the vertical axis represents voltage. The displacement signal processing unit 630 outputs sound signals in the range of 0V to 3.3V. The reference voltage is 1.65V. The signal value after A / D conversion is shown in parentheses on the vertical axis of Graph 1202.

[0089] The "Operating Mode" in Figure 12 represents the operating mode of the electronic stethoscope 100. The "Volume Up Button" in Figure 12 indicates the timing when the volume up button 123a is pressed, represented by a high level. The "Volume Index for Heartbeat Sound Mode" in Figure 12 represents the volume index set for heartbeat sound mode. The "Volume Index for Respiratory Sound Mode" in Figure 12 represents the volume index set for respiratory sound mode.

[0090] Graph 1203 shows the waveform of the sound signal converted in S802 of Figure 8. The horizontal axis of Graph 1203 represents time, and the vertical axis of Graph 1203 represents the value of the sound signal.

[0091] Assume that before time t1, the volume indices for both the heart sound mode and the respiratory sound mode are "0". Also, assume that before time t1, the electronic stethoscope 100 is in heart sound mode.

[0092] At time t1, in response to the volume up button 123a being pressed, the processor 601 increments the volume index of the heartbeat sound mode to "1". Meanwhile, the processor 601 maintains the volume index of the respiratory sound mode at "0".

[0093] At time t2, the pressure state of the diaphragm 206 transitions from unused to used, and sound (e.g., heartbeat sound) is transmitted from the biological surface 300 through the diaphragm 206. The electronic stethoscope 100 is in heartbeat sound mode, and the volume index for heartbeat sound mode is "1", so according to the correspondence table 1000, the magnification Mv becomes "0.4". The sound signal is converted using this magnification Mv. At time t3, the pressure state of the diaphragm 206 transitions from used to unused.

[0094] At time t4, in response to the mode switching button 123c being pressed, the processor 601 transitions the electronic stethoscope 100 from heart sound mode to respiratory sound mode.

[0095] At time t5, in response to the volume up button 123a being pressed, the processor 601 increments the volume index of the respiratory sound mode to "1". Meanwhile, the processor 601 maintains the volume index of the heartbeat sound mode at "1".

[0096] At time t6, the pressure state of the diaphragm 206 transitions from unused to used, and sound (e.g., respiratory sounds) is transmitted from the biological surface 300 through the diaphragm 206. The electronic stethoscope 100 is in respiratory sound mode, and the volume index for respiratory sound mode is "1", so according to the correspondence table 1000, the magnification Mv becomes "0.31". The sound signal is converted using this magnification Mv. At time t7, the pressure state of the diaphragm 206 transitions from used to unused.

[0097] In the example shown in Figure 12, the volume index is changed separately for the heart sound mode and the respiratory sound mode. As described above, the volume index may also be changed synchronously for the heart sound mode and the respiratory sound mode. In this case, at time t1, both the volume index for the heart sound mode and the volume index for the respiratory sound mode are incremented to "1". Furthermore, as a synchronous change method, the processor 601 holds a single volume index Iv in the RAM 604 and selects a multiplier Mv corresponding to Iv according to the operating mode. Specifically, when the electronic stethoscope 100 is in heart sound mode, the multiplier Mv (heartbeat) corresponding to Iv is selected from the mapping for heart sound mode in the correspondence table 1000, and when the electronic stethoscope 100 is in respiratory sound mode, the multiplier Mv (respiration) corresponding to Iv is selected from the mapping for respiratory sound mode in the correspondence table 1000. When switching modes, Iv itself is not changed; only the selected multiplier Mv is switched according to the mode. When Iv is incremented or decremented by volume up / down operation, the mapping reference results for both modes are updated simultaneously. Within the range of possible values ​​for Iv (e.g., "-3" to "2"), saturation operation (maintaining the maximum / minimum value) is performed when the boundary value is exceeded.

[0098] According to the embodiment described above, for each of the multiple operating modes for detecting vibrations in different frequency bands, a volume parameter (magnification Mv in the above example) for adjusting the volume of the electronic stethoscope 100 is determined individually. This makes it possible to change the volume while taking into account the characteristics of human hearing.

[0099] In the electronic stethoscope 100 described above, a vibration detection unit for detecting vibrations of the diaphragm 206 is configured by a light-emitting element 202 (light source), a light-receiving element 204, a light-reflecting unit 207, and a displacement signal processing unit 630. The methods shown in Figures 8, 9, and 12 may be performed by electronic stethoscopes with other configurations. For example, the methods shown in Figures 8 and 9 may be performed by an electronic stethoscope having a vibration detection unit (e.g., a microphone or piezoelectric element) for detecting air vibrations caused by the vibration of the diaphragm. In this case, the pressure on the diaphragm by the biological surface may be detected using an acceleration sensor or a contact sensor.

[0100] (Other Embodiments) The present invention can also be realized by supplying a program that implements one or more of the functions of the above embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that implements one or more functions.

[0101] The technical ideas derived from this disclosure are not limited to the exemplary embodiments disclosed, but are intended to encompass various modifications of the exemplary embodiments, or substitutions with equivalent structures or functions. The scope of the following claims should be interpreted in the broadest way to encompass all such modifications and equivalent structures and functions.

[0102] This application claims priority based on Japanese Patent Application No. 2024-221000, filed on 17 December 2024, and all of its contents are incorporated herein by reference.

Claims

1. A detection device for detecting vibrations of a subject, comprising: a diaphragm that displaces in accordance with the vibrations of the subject; a generation means for generating acoustic data representing a sound signal based on vibrations transmitted from the subject through the diaphragm; a determination means for determining the value of an adjustment parameter for adjusting the volume based on a set volume level of the detection device; and a change means for changing the set level in accordance with an instruction to change the volume obtained from a user, wherein the detection device is operable in a first mode for detecting vibrations in a first frequency band and a second mode for detecting vibrations in a second frequency band different from the first frequency band, and characterized in that, for the same numerical set level, the value of the adjustment parameter used when the detection device is in the first mode and the value of the adjustment parameter used when the detection device is in the second mode are different from each other.

2. The detection device according to claim 1, characterized in that the first frequency band includes frequencies in the range of 30 Hz to 300 Hz, and the second frequency band includes frequencies in the range of 500 Hz to 2 kHz.

3. The detection device according to claim 1 or 2, characterized in that the first mode is a mode for detecting heart sounds, and the second mode is a mode for detecting respiratory sounds.

4. The detection device according to any one of claims 1 to 3, characterized in that the changing means independently changes the setting level for the first mode and the second mode, respectively.

5. The detection device according to any one of claims 1 to 4, characterized in that the changing means synchronously changes the setting level for the first mode and the second mode.

6. The detection device according to any one of claims 1 to 5, further comprising a transmission means for transmitting the acoustic data to an external device.

7. The detection device according to any one of claims 1 to 6, wherein the generating means generates the acoustic data by converting an acoustic signal representing the sound transmitted from the subject to the diaphragm into a predetermined format, and the adjustment parameter is used for converting the acoustic signal.

8. The detection device according to claim 7, characterized in that the adjustment parameter is a multiplier applied to the amplitude of the sound signal.

9. The detection device according to any one of claims 1 to 8, wherein the diaphragm includes a reflective surface that moves in response to the vibration of the object being tested, and the detection device further comprises a light-emitting element that emits light toward the reflective surface, and a light-receiving element that receives the reflected light reflected by the reflective surface and outputs a signal corresponding to the reflected light.

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