Electronic stethoscope

Abstract

It generates high-quality audio data with a simple configuration. [Solution] The electronic stethoscope includes a diaphragm that vibrates together with the object to be measured when it comes into contact with the object to be measured; a vibration detection unit that detects the vibration of the diaphragm and outputs a signal corresponding to the vibration; a pressure detection unit that detects the pressure applied to the diaphragm by the object to be measured; a generation unit that generates sound data corresponding to the vibration of the diaphragm based on the signal output from the vibration detection unit; and a correction unit that corrects the sound data based on a reference value determined based on the signal output from the vibration detection unit when no pressure is detected on the diaphragm by the object to be measured.

Description

[Technical Field]

[0001] This invention relates to an electronic auscultation device. [Background technology]

[0002] In recent years, electronic stethoscopes equipped with sensors for measuring biological vibrations and capable of acquiring biological sounds using these sensors have begun to become widespread. Patent Document 1 describes a stethoscope in which the temperature characteristics of the cantilever are determined in advance, the actual temperature is detected by a temperature sensor, and a temperature compensation correction calculation is applied to the output signal from the detection unit based on the detected value. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2014-142323 [Overview of the project] [Problems that the invention aims to solve]

[0004] If a temperature sensor is installed to compensate for changes in signal values ​​in response to the heat generation of electronic and electrical components in an electronic stethoscope, the circuit board of the electronic stethoscope becomes larger, and the manufacturing cost of the electronic stethoscope increases. One aspect of the present invention aims to provide a technology for generating high-quality sound data with a simple configuration. [Means for solving the problem]

[0005] According to some embodiments, an electronic stethoscope is provided, comprising: a diaphragm that vibrates together with an object to be measured when the object to be measured comes into contact with the diaphragm; vibration detection means for detecting the vibration of the diaphragm and outputting a signal corresponding to the vibration; pressure detection means for detecting the pressure applied to the diaphragm by the object to be measured; generation means for generating sound data corresponding to the vibration of the diaphragm based on the signal output from the vibration detection means; and correction means for correcting the sound data based on a reference value determined based on the signal output from the vibration detection means while the pressure applied to the diaphragm by the object to be measured is not detected. [Effects of the Invention]

[0006] The above embodiment enables the generation of high-quality sound data with a simple configuration. [Brief explanation of the drawing]

[0007] [Figure 1] A schematic diagram illustrating an example of the appearance of an electronic stethoscope in some embodiments. [Figure 2] A schematic diagram illustrating an example of the configuration of a chestpiece in some embodiments. [Figure 3] A schematic diagram illustrating an example of the operation of the chestpiece in some embodiments. [Figure 4] A schematic diagram illustrating an example of the movement of reflected light in some embodiments. [Figure 5] A diagram illustrating the relationship between displacement amount and displacement signal in some embodiments. [Figure 6] A block diagram illustrating an example of the circuit configuration of an electronic stethoscope in some embodiments. [Figure 7] A block diagram illustrating an example of the functional configuration of an electronic stethoscope in some embodiments. [Figure 8] A flowchart illustrating an example method for determining reference values ​​in some embodiments of an electronic auscultation device. [Figure 9] A flowchart illustrating an example method for data generation processing of an electronic stethoscope in some embodiments. [Figure 10]A diagram illustrating an example of sound signal data from an electronic stethoscope in some embodiments. [Modes for carrying out the invention]

[0008] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, 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.

[0009] [Appearance of an electronic stethoscope] Referring to Figure 1, the appearance of the electronic stethoscope 100 according to one embodiment will be described. In Figure 1 and some of the 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 stethoscope 100 when viewed from a certain direction. The electronic stethoscope 100 is a medical device used by doctors, nurses, etc., as a diagnostic instrument to listen to internal sounds of the body. The electronic stethoscope 100 is mainly used to listen to heart sounds and respiratory sounds.

[0010] 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.

[0011] The gripping portion 120 is gripped when the user of the electronic stethoscope 100 presses the diaphragm 206 against the living body surface. The gripping portion 120 has a rod shape, and the chest piece 110 is attached to one end (the negative x-axis direction in FIG. 1). The gripping portion 120 has a housing 121, and a battery and a circuit board are accommodated inside the housing 121. Circuit elements for controlling the operation of the electronic stethoscope 100 are mounted on the circuit board. The gripping portion 120 further has a display portion 122, an operation portion 123, a power switch 124, and a connector 125.

[0012] The display portion 122 has a plurality of indicators, and each indicator displays the state of the electronic stethoscope 100. For example, states such as the power-on state, the current operation mode, the communication state with the computer, and whether the chest piece 110 is pressed against the living body surface are notified by these indicators.

[0013] The operation portion 123 has a plurality of physical buttons for receiving settings of the electronic stethoscope 100, and receives operations from the user via these buttons. Specifically, the operation portion 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 operation mode of the electronic stethoscope 100. The electronic stethoscope 100 can operate by switching among a plurality of operation modes including a heartbeat sound mode, a breathing sound mode, and a power saving mode. The heartbeat sound mode is an operation mode for listening to the heartbeat sound. The breathing sound mode is an operation mode for listening to the breathing sound. The power saving mode is an operation mode with less power consumption than the heartbeat sound mode and the breathing sound mode. Further, the electronic stethoscope 100 acquires an instruction to start or end recording by a long press operation of the mode switching button 123c.

[0014] The power switch 124 is a switch that switches the power of the electronic stethoscope 100 on and off. The connector 125 is a connector for receiving a cable or a connector of an external device. Through the connector 125, power is supplied from an external device to the battery included in the grip portion 120.

[0015] [Cross-sectional configuration of the chest piece of the electronic stethoscope] Referring to FIG. 2, a configuration example of the chest piece 110 will be described. The upper side of FIG. 2 shows a cross-sectional view of the chest piece 110, and the lower side of FIG. 2 shows a plan view of the chest piece 110. In the plan view, only the light-emitting circuit board 203, the light-receiving circuit board 205, the diaphragm 206, and the light reflection portion 207 are shown in order to clarify the positional relationship of the components.

[0016] The chest piece 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 reflection portion 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 reflection portion 207 inside. Since the throttle portions 209 and 210 are formed in the holding member 201, the housing 208 also houses the throttle portions 209 and 210 inside. The diaphragm 206 forms a part of the exterior of the electronic stethoscope 100 together with the housing 208.

[0017] 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 a power source (battery of the grip portion 120) outside the chest piece 110. The light-emitting element 202 is mounted on the light-emitting circuit board 203. On the light-emitting circuit board 203, a peripheral circuit for defining the light emission amount of the light-emitting element 202 and a power terminal for receiving power supply from a power source outside the chest piece 110 are mounted.

[0018] 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 comes 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.

[0019] 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.

[0020] 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 a 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, which 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.

[0021] 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.

[0022] 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 in which the opening is formed corresponds to the diaphragm portion 209.

[0023] 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, allowing 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.

[0024] The housing 208 is attached to the upper outer surface of the retaining 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.

[0025] [Example of electronic stethoscope operation] Referring to Figure 3, an example of the operation of the chestpiece 110 of the electronic stethoscope 100 will be described. As shown in Figure 3, 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.

[0026] Figure 3(a) 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 such 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.

[0027] Figure 3(b) 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. Consequently, 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 3(b), since the reflected light 212 does not reach the photodetector 204 at all, the value of the displacement signal is ideally zero.

[0028] 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.

[0029] [Relationship between diaphragm displacement and the displacement of the reflected light receiving position in an electronic stethoscope] Referring to Figure 4, the relationship between the displacement of the biological surface 300, the incident angle of the incident light 211, the incident angle of the 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 is considered the reference position when the diaphragm 206 is flat. Position 402 indicates the position where the upper surface of the light-reflecting part 207 is displaced upward by a displacement of d2 from position 401. Since the displacement d2 of the light-reflecting part 207 is small, the upper surface of the light-reflecting part 207 is considered flat even when it is at position 402.

[0030] In Figure 4, 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 element 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 element 207. When the upper surface of the light-reflecting element 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 element 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 element 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 of the position where the light-receiving element 204 receives the reflected light 212 is denoted as d3. The displacement d3 may also be defined by the displacement 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 d3 to the displacement d2 is denoted as the displacement ratio G. In this case, G=2×sinθ / cosφ…(Formula 1) The following relationship holds true. Therefore, even if the displacement d2 of the light reflecting part 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.

[0031] 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 is: G=2×sinθ…(Formula 2) Therefore, the larger the angle of incidence θ, the larger the displacement d3 becomes.

[0032] 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.

[0033] [Relationship between displacement amount and displacement signal on the biological surface of an electronic stethoscope] Referring to Figure 5, the relationship between the displacement of the biological surface 300 and the displacement signal will be explained. 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 of the biological surface 300 and the displacement signal. The horizontal axis of graph 500 represents the displacement of the biological surface 300 and the displacement signal generated by the light-receiving circuit board 205.

[0034] 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 Figure 3, 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, Sd=Vmax-k×d3…(Formula 3) This is the result. Here, Vmax is the value of the displacement signal when the displacement amount 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 light receiving circuit board 205. By substituting d3 = G × d2 and equation 1 into equation 3, Sd=Vmax-2k×d2×sinθ / cosφ…(Formula 4) This is obtained. Therefore, the displacement signal Sd decreases monotonically and linearly as the displacement amount d2 of the biological surface 300 increases, as shown in graph 500. 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.

[0035] 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.

[0036] 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., heart sounds) 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 sound 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.

[0037] [Example of circuit configuration for an electronic stethoscope] Referring to Figure 6, an example of the circuit configuration of the electronic stethoscope 100 will be described. The microcontroller 600 is a control means that controls the overall operation of the electronic stethoscope 100. In Figure 6, the electronic stethoscope 100 includes one microcontroller 600. Alternatively, the electronic stethoscope 100 may include multiple microcontrollers 600. The microcontroller 600 includes a processor 601, a non-volatile memory 602, a Bluetooth® circuit 603, and RAM 604. The processor 601 controls the operation of the electronic stethoscope 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 stethoscope 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 compliant with 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.

[0038] 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 photodetector 204 to an external audio output device 670 via the wireless communication unit 618 or the wired communication unit 617. The audio output device 670 is, for example, a wired or wireless earphone or headphones. In addition to transmitting audio signal data to the audio output device 670, the microcontroller 600 can also transmit audio signal data to a computer 680 (for example, a personal computer, smartphone, tablet, etc.). The audio signal data represents sounds generated in the living body (i.e., biosound). The audio signal data is also called sound data. Doctors, nurses, and public health nurses can listen to the biosound represented by the audio signal converted from the audio signal data using the audio output device 670 or the computer 680.

[0039] The displacement signal output from the photodetector 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 sound signal data for wireless communication. The wireless communication unit 618 then transmits the sound signal data to the sound output device 670. The sound output device 670, upon receiving the sound signal data, outputs a sound corresponding to that sound signal data.

[0040] Although the electronic stethoscope 100 described above is capable of transmitting sound signal data via both wireless and wired communication, it may also be capable of transmitting sound signal data via only one of these communication methods. Transmission of sound signal data to the computer 680 is similar to transmission of sound signal data to the sound output device 670. The computer 680 can also visually display waveform data generated based on the received sound signal data. The waveform data may be generated by the computer 680 or by the electronic stethoscope 100. Furthermore, some or all of the signal processing and sound output processing by the electronic stethoscope 100 may be performed by an external device (e.g., the sound output device 670 or the computer 680).

[0041] The UART integrated circuit 620 is connected to the microcontroller 600 and to the connector 125 (specifically, its data terminals). The UART integrated circuit 620 performs UART-compliant communication. The UART integrated circuit 620 and the connector 125 function as a wired communication unit 617. The microcontroller 600 may communicate with external devices via wires through the UART integrated circuit 620 and the connector 125. The UART integrated circuit 620 may also be connected to the power terminals of the connector 125. A voltage VBUS may be applied to the UART integrated circuit 620 through the power terminals of the connector 125 from an external device connected to the connector 125 (e.g., a charger or computer 680). The UART integrated circuit 620 may be able to operate with the voltage VBUS as its operating voltage.

[0042] 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 multiple circuit elements included in the electronic stethoscope 100. The power supply unit 610 may supply power at multiple different voltages. Alternatively, the power supply unit 610 may supply power at a single voltage, and the voltage may be reduced in front of each circuit element to obtain an appropriate operating voltage.

[0043] Battery 611 stores electrical energy used by the electronic stethoscope 100. 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 battery 611 and the discharging of battery 611. For example, the charging integrated circuit 612 charges battery 611 using electrical energy supplied from an external device such as a charger or computer 680 connected to connector 125. The charging integrated circuit 612 also supplies the electrical energy stored in 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.

[0044] The boost converter 613 boosts a DC voltage to another DC voltage of a different 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 accelerometer 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.

[0045] The load switch 615 is a switch that switches between on (conducting state) and off (non-conducting 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 an LDO. The voltage regulator 616 generates the operating voltage for some of the circuit elements of the electronic stethoscope 100. The voltage generated by the voltage regulator 616 is denoted as voltage V2. The voltage regulator 616 may also generate the operating voltage for the light-emitting element 202 and the light-receiving element 204, for example, voltage V2 is 5.8V. In the example in Figure 6, voltage V2 is applied to the light-emitting element 202 and the light-receiving element 204, respectively. Power is supplied to the light-emitting element 202 and the light-receiving element 204 from the voltage regulator 616 of the power supply unit 610. The voltage regulator 616 outputs voltage V2 when a voltage high enough for voltage V2 is applied to its input terminal. Therefore, the voltage regulator 616 outputs voltage V2 when the load switch 615 is ON. The voltage regulator 616 does not output voltage V2 when the load switch 615 is OFF. When the voltage regulator 616 does not output voltage V2, the potential of the output terminal of the voltage regulator 616 is ground potential.

[0046] The displacement signal processing unit 630 processes the diaphragm displacement signal to generate an audio signal representing the sound transmitted from the biological surface to 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 to generate 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).

[0047] 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.

[0048] The buffer circuit 631 receives a displacement signal from the photodetector 204 and outputs that 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.

[0049] HPF632 outputs a signal to amplifier circuit 633 obtained by attenuating the low-frequency components (i.e., frequency components lower than a specific cutoff frequency) of the displacement signal received from buffer circuit 631 and passing the high-frequency components (i.e., frequency components higher than the said cutoff frequency) of the displacement signal. HPF632 attenuates components below 10Hz from the displacement signal received from buffer circuit 631, so the cutoff frequency of HPF632 is set to, for example, 10Hz. However, the cutoff frequency may be a value greater than 10Hz, for example, 15Hz or 20Hz. Also, the cutoff frequency may be 10Hz or more and less than 20Hz. Therefore, HPF632 removes or attenuates components below 10Hz from the displacement signal received from buffer circuit 631.

[0050] 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 a component caused by the user's hand tremors when using the electronic stethoscope 100. The low-frequency noise may also include a change in the DC component due to the diaphragm 206 being pressed against the biological surface. Such low-frequency noise has a much larger amplitude than the component originating from vibrations transmitted from the biological surface to the diaphragm 206 (hereinafter referred to as the biological component). Therefore, by amplifying the displacement signal from which the low-frequency noise has been suppressed, the biological component can be appropriately acquired within the dynamic range of the amplification circuit. Alternatively, a bandpass filter that removes components below at least 10 Hz may be used instead of the HPF632.

[0051] [Example of an electronic stethoscope's functional configuration] 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).

[0052] 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.

[0053] 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.

[0054] The pressure detection unit 705 detects that the diaphragm 206 is being pressed or in contact with something based on the displacement signal obtained from the displacement signal processing unit 630. 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 identifies 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 in close contact with the biological surface. The use state is the pressing state when the user is pressing the diaphragm 206 in close contact with the biological surface. The amount of displacement of the diaphragm 206 in the not-use state is smaller than the amount of displacement of the diaphragm 206 in the use state. Therefore, the pressure detection unit 705 determines that the pressing state is the not-use state when the amount of 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 pressure state is in use when the amount of displacement of the diaphragm 206 exceeds the threshold.

[0055] 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 heart 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 heart 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 heart sound mode is referred to as the heart 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.

[0056] The output control unit 706 performs signal processing on the sound signal before outputting the sound signal. Specifically, the output control unit 706 includes a reference value determination unit 711 and a data generation unit 712. The reference value determination unit 711 determines a reference value for the sound signal to generate sound signal data based on the sound signal generated while the diaphragm 206 is not in use. The data generation unit 712 generates sound signal data to represent the value of the sound signal relative to the reference value. For example, the data generation unit 712 converts the data format of the sound signal to PCM format so that the volume of the reference value is 0. Details of the processing of the reference value determination unit 711 and the data generation unit 712 will be described later.

[0057] The volume control unit 707 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 707 adjusts the volume based on user input acquired by the input acquisition unit 703. For example, the volume control unit 707 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 707 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.

[0058] The volume control unit 707 also adjusts the volume based on the pressing state. For example, the volume control unit 707 can set the volume to a normal level when the diaphragm 206 is pressed above a certain level by the object being measured (i.e., it is determined to be in use). The operation of setting the volume based on the pressing state will be described later. The normal level volume is a volume suitable for listening to the sound signal reproduced by the sound output device 670. The volume control unit 707 adjusts the normal level value based on the user input acquired by the input acquisition unit 703.

[0059] The volume control unit 707 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 volume means a volume that is zero or lower than the normal level volume. For example, the mute level volume may be so low that it is not suitable for listening to the sound signal played back by the sound output device 670. The mute level can also be a constant multiple of the normal level (e.g., 10%). When the mute level is configured to depend on the normal level in this way, if the normal level changes due to user input via the volume control buttons included in the operation unit 123, for example, the mute level will also change depending on the normal level. On the other hand, the mute level can also be set independently of the normal level. When the mute level is independent of the normal level, even if the normal level changes due to user input, for example, the mute level will not change.

[0060] The volume control unit 707 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 707 may adjust the volume level of the sound signal by adjusting the digital value of the sound signal output by the output control unit 706.

[0061] [Method for determining reference values] Referring to Figure 8, a method for determining a reference value for an audio signal to generate audio signal data will be described. 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 electronic stethoscope 100 is powered on and ends the method in Figure 8 when the electronic stethoscope 100 is powered 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 (e.g., heart sound mode or respiratory sound mode) and end the method in Figure 8 when the electronic stethoscope 100 transitions to power-saving mode.

[0062] In S801, processor 601 initializes the reference value of the sound signal. The reference value of the sound signal is the value of the sound signal generated by the displacement signal processing unit 630 when no vibration is occurring in the diaphragm 206 (for example, when the diaphragm 206 is not pressed or when the biological surface 300 in contact with the diaphragm 206 is stationary). As will be described later, when the sound signal is at the reference value, the sound signal data is generated to represent a silent state. In the following description, the value of the sound signal may be referred to as the signal value, and the reference value of the sound signal may be referred to as the reference signal value.

[0063] For example, the processor 601 (e.g., the reference value determination unit 711) uses a reference value set during the manufacture of the electronic stethoscope 100 and stored in the non-volatile memory 602 as the initial value of the reference signal value. However, the reference signal value may change depending on the heat generated by the electronic and electrical components contained in the electronic stethoscope 100. In particular, with a small handheld device like the electronic stethoscope 100, the heat generated by the electronic stethoscope 100 is not easily released to the outside when the user holds the electronic stethoscope 100 in a way that covers it, resulting in significant heat generation from the electronic and electrical components contained in the electronic stethoscope 100. Therefore, the processor 601 updates the reference signal value in a step described later.

[0064] In the example described above, the reference value set during the manufacture of the electronic stethoscope 100 is used as the initial value. Alternatively, the reference value determined when the method shown in Figure 8 was previously performed may be used as the initial value.

[0065] In S802, the processor 601 (for example, the reference value determination unit 711) acquires the signal value output from the displacement signal processing unit 630. As described above, the displacement signal processing unit 630 generates an audio signal based on the displacement signal generated by the photodetector 204. This audio signal represents the vibration of the diaphragm 206. The A / D converter 605 of the processor 601 digitizes the acquired signal value. For example, the A / D converter 605 converts the signal value into a 12-bit digital value. In this case, the signal value is in the range of 0 to 4095.

[0066] In S803, the processor 601 (for example, the pressure detection unit 705) determines whether pressure on the diaphragm 206 by the biological surface 300 has been detected. If the processor 601 determines that pressure on the diaphragm 206 by the biological surface 300 has been detected (YES in S803), it proceeds to S805; otherwise (NO in S803), it proceeds to S804. The pressure detection unit 705 determines that pressure on the diaphragm 206 has not been detected if the amount of displacement of the diaphragm 206, as determined from the displacement signal, is less than a threshold. On the other hand, the pressure detection unit 705 determines that pressure on the diaphragm 206 has been detected if the amount of displacement of the diaphragm 206 exceeds the threshold.

[0067] In S804, the processor 601 (for example, the reference value determination unit 711) determines a reference signal value based on the latest signal value acquired in S802 and stores this reference signal value in RAM 604. If a reference signal value is already stored in RAM 604, the processor 601 overwrites it with the newly determined reference signal value.

[0068] For example, processor 601 determines the most recent signal value obtained in the immediately preceding execution of S802 as the reference signal value. Alternatively, to mitigate the influence of noise contained in the sound signal, processor 601 may determine the average value of multiple signal values ​​obtained in S802 executions up to that point as the reference signal value. The multiple signal values ​​used to calculate the average value include the most recent signal value.

[0069] For example, the average of multiple signal values ​​is a moving average of sound signals over a predetermined period or a predetermined number of values. For example, processor 601 determines the average of the most recently acquired n signal values ​​as the reference signal value. Processor 601 stores this signal value in RAM 604 each time it acquires a signal value in S802 and uses it to calculate the moving average. Processor 601 deletes signal values ​​from RAM 604 that are no longer needed for calculating the moving average.

[0070] The processor 601 may determine a value in a predetermined frequency band of the sound signal generated while the pressure on the diaphragm 206 by the biological surface 300 is not detected as a reference signal value. This predetermined frequency band is, for example, a frequency band that includes a DC component. For example, the processor 601 determines a value obtained by applying a low-pass filter to the waveform of the sound signal over a predetermined period of time as the reference signal value. A Gaussian filter may be used as the low-pass filter.

[0071] In S805, the processor 601 (for example, the reference value determination unit 711) waits for a predetermined time. For example, the predetermined time may be 44.1 kHz, which is commonly used as an audio sampling rate for earphones, i.e., about 23 microseconds, or 16 kHz, which is commonly used as an audio sampling rate for headsets, i.e., about 63 microseconds.

[0072] Subsequently, processor 601 returns processing to S802. In this manner, processor 601 repeatedly executes S802 to S805. While no pressure on the diaphragm 206 by the biological surface 300 is detected, S804 (updating the reference signal value) is repeatedly executed. The iteration of S804 continues until pressure on the diaphragm 206 by the biological surface 300 is detected. On the other hand, while pressure on the diaphragm 206 by the biological surface 300 is detected, S804 (updating the reference signal value) is not executed. This reduces the computational load.

[0073] [Sound signal data generation process] Referring to Figure 9, a method for generating sound signal data 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 electronic stethoscope 100 is powered on and ends the method in Figure 9 when the electronic stethoscope 100 is powered 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 (e.g., heart sound mode or respiratory sound mode) and end the method in Figure 9 when the electronic stethoscope 100 transitions to power-saving mode. The method in Figure 9 is executed in parallel with the method in Figure 8.

[0074] In S901, the processor 601 (for example, the data generation unit 712) acquires the signal value output from the displacement signal processing unit 630. As described above, the displacement signal processing unit 630 generates an audio signal based on the displacement signal generated by the photodetector 204. This audio signal represents the vibration of the diaphragm 206. The A / D converter 605 of the processor 601 digitizes the acquired signal value. For example, the A / D converter 605 converts the signal value into a 12-bit digital value. In this case, the signal value is in the range of 0 to 4095.

[0075] In S902, the processor 601 (for example, the data generation unit 712) generates sound signal data to represent the latest signal value relative to the reference signal value determined by the method shown in Figure 8. The latest signal value is the signal value acquired in the immediately preceding execution of S901. The processor 601 reads the reference signal value stored in RAM 604 and uses it for processing in S902. As described above, the reference signal value stored in RAM 604 is the latest reference signal value determined up to the time when the pressure on the diaphragm 206 by the biological surface 300 is detected. Therefore, sound signal data is generated using a reference signal value corresponding to the current heat generation state of the electronic and electrical circuits included in the electronic stethoscope 100.

[0076] Let the reference signal value be V R , and represent the latest signal value as V. The processor 601, for example, S = k(V - V R ) … (Equation 5) calculates the current value S of the audio signal data according to this. Here, k is a coefficient for conversion to the PCM format. The PCM format is a signed integer. Assuming that the audio signal data is represented, for example, in 16 bits, the value of the audio signal data is included in the range of -32768 to 32767. The period during which the value of the audio signal data is 0 is a silent state. Therefore, when the value of the audio signal is the reference signal value, the audio signal data represents a silent state.

[0077] Instead of Equation 5, the processor 601 S m = k(V R - V I ) … (Equation 6) S = k(V - V I ) - S m … (Equation 7) may calculate the latest value S of the audio signal data according to this. V in Equation 6 and Equation 7 I represents the reference signal value set during manufacturing. S m is a correction value for correcting the audio signal data. k(V - V I ) in Equation 7 represents the value of the audio signal data generated using the reference signal value set during manufacturing. As described above, the reference signal value set during manufacturing may not represent a silent state depending on the current heat generation state of the electronic circuits and electrical circuits included in the electronic stethoscope 100. Therefore, in Equation 7, the audio signal data is corrected using S m .

[0078] In S903, the processor 601 (for example, the data generation unit 712) outputs the latest value of the audio signal data generated in S902 to the Bluetooth circuit 603. The Bluetooth circuit 603 outputs this value to an external device (the audio output device 670 or the computer 680) through the wireless communication unit 618.

[0079] In S904, the processor 601 (for example, the data generation unit 712) waits for a predetermined time. For example, the predetermined time may be 44.1 kHz, which is commonly used as an audio sampling rate for earphones, i.e., about 23 microseconds, or 16 kHz, which is commonly used as an audio sampling rate for headsets, i.e., about 63 microseconds.

[0080] Subsequently, processor 601 returns processing to S901. In this way, processor 601 repeatedly executes S901 to S904. As a result, the audio signal data is output to an external device in real time.

[0081] [Specific examples of reference signal values ​​and audio signal data] Referring to Figure 10, specific examples of the reference signal value determined in Figure 8 and the sound signal data generated by the method in Figure 9 will be explained. Graph 1001 shows the waveform of the displacement signal output from the photodetector 204. The horizontal axis of Graph 1001 represents time, and the vertical axis represents voltage. The threshold Th1 is the voltage used to determine whether the diaphragm 206 is being pressed by the biological surface 300. In the example in Figure 10, for the period before time t1 and after time t2, the displacement signal is greater than the threshold Th1, so it is determined that no pressure on the diaphragm 206 by the biological surface 300 is detected. For the period from time t1 to time t2, the displacement signal is less than the threshold Th1, so it is determined that pressure on the diaphragm 206 by the biological surface 300 is detected.

[0082] Graph 1002 shows the waveform of the sound signal output from the displacement signal processing unit 630. The horizontal axis of Graph 1002 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. Assume that the reference signal value set during the manufacture of the electronic stethoscope 100 is 1.65V.

[0083] Graph 1003 shows the waveform of the sound signal data generated by processor 601. The horizontal axis of graph 1003 represents time, and the vertical axis of graph 1003 represents the value of the sound signal data.

[0084] Figures 8 and 9 are executed over the time shown in Figure 10. Until time t1 is reached, no pressure is detected on the diaphragm 206, so the sound signal shown in graph 1002 should represent silence. However, depending on the heat generation of the electronic and electrical components contained in the electronic stethoscope 100, the value of the sound signal will be different from the reference signal value (1.65V) set during the manufacture of the electronic stethoscope 100 (1.7V in the example in Figure 10). In the method of Figure 8, the reference signal value is determined based on the sound signal until time t1 is reached. Since the sound signal data is generated using the method of Figure 9 with this reference signal value, the value of the sound signal data becomes 0 in the silence state, as shown in graph 1003.

[0085] As described above, the electronic stethoscope 100 generates high-quality sound signal data such that the diaphragm 206 is silent when it is not vibrating, even if the characteristics of the electronic and electrical components included in the electronic stethoscope 100 change due to heat generation or aging. Furthermore, since the electronic stethoscope 100 does not require a temperature sensor to generate such high-quality sound signal data, it can generate high-quality sound signal data with a simple configuration.

[0086] 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 and 9 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.

[0087] [Summary of Embodiments] (Item 1) A diaphragm that vibrates together with the object to be measured when the object to be measured comes into contact with it, A vibration detection means that detects vibrations of the diaphragm and outputs a signal corresponding to the vibrations, A pressure detection means for detecting the pressure applied to the diaphragm by the object being measured, A generation means that generates sound data corresponding to the vibration of the diaphragm based on the signal output from the vibration detection means, A correction means for correcting the sound data based on a reference value determined based on the signal output from the vibration detection means while the pressure on the diaphragm by the object under measurement is not detected, An electronic stethoscope characterized by being equipped with the following features. (Item 2) The electronic auscultation device according to item 1, characterized in that when the value of the signal output from the vibration detection means is the reference value, the sound data represents a silent state. (Item 3) The electronic auscultation device according to item 1 or 2, characterized in that the reference value is the average value of multiple values ​​of the signal output from the vibration detection means while the pressing of the diaphragm by the object to be measured is not detected. (Item 4) The electronic auscultation device according to item 3, characterized in that the average value of the plurality of values ​​of the signal is a moving average value of the signal over a predetermined period or a predetermined number of times. (Item 5) The electronic auscultation device according to item 1 or 2, characterized in that the reference value is a value in a predetermined frequency band of the signal output from the vibration detection means while the pressing of the diaphragm by the object to be measured is not detected. (Item 6) The correction means is The reference value is repeatedly determined until the pressure on the diaphragm by the object being measured is detected. The electronic auscultation device according to any one of items 1 to 5, characterized in that it corrects the sound data based on the latest reference value determined before the pressure of the diaphragm by the object being measured is detected. (Item 7) The electronic auscultation device according to any one of items 1 to 6, characterized in that the correction means does not determine the reference value while the pressure on the diaphragm by the object to be measured is detected. (Item 8) The vibration detection means is A light-reflecting portion is provided on the surface of the diaphragm opposite to the contact surface that contacts the object to be measured, Light source and A light-receiving element having a light-receiving surface that receives light emitted from the light source and specularly reflected by the light-reflecting part, and generating a signal corresponding to the light that reaches the light-receiving surface, The electronic auscultation device according to any one of items 1 to 7, comprising: a signal processing unit that generates a signal corresponding to the vibration of the diaphragm based on the signal generated by the light-receiving element. (Item 9) The electronic auscultation device according to item 8, characterized in that the pressure detection means detects the pressure on the diaphragm by the object to be measured based on the signal generated by the light receiving element. (Item 10) The electronic auscultation device according to any one of items 1 to 9, further comprising output means for outputting the sound data to an external device.

[0088] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention. [Explanation of Symbols]

[0089] 100 Electronic stethoscope, 202 Light-emitting element, 204 Photodetector, 206 Diaphragm

Claims

1. A diaphragm that vibrates together with the object to be measured when the object to be measured comes into contact with it, A vibration detection means that detects vibrations of the diaphragm and outputs a signal corresponding to the vibrations, A pressure detection means for detecting the pressure applied to the diaphragm by the object being measured, A generation means that generates sound data corresponding to the vibration of the diaphragm based on the signal output from the vibration detection means, A correction means for correcting the sound data based on a reference value determined based on the signal output from the vibration detection means while the pressure on the diaphragm by the object under measurement is not detected, An electronic stethoscope characterized by being equipped with the following features.

2. The electronic auscultation device according to claim 1, characterized in that when the value of the signal output from the vibration detection means is the reference value, the sound data represents a silent state.

3. The electronic auscultation device according to claim 1, characterized in that the reference value is the average value of a plurality of signals output from the vibration detection means while the pressing of the diaphragm by the object to be measured is not detected.

4. The electronic auscultation device according to claim 3, characterized in that the average value of the plurality of values ​​of the signal is a moving average value of the signal over a predetermined period or a predetermined number of values.

5. The electronic auscultation device according to claim 1, characterized in that the reference value is a value in a predetermined frequency band of the signal output from the vibration detection means while the pressing of the diaphragm by the object to be measured is not detected.

6. The correction means is The reference value is repeatedly determined until the pressure on the diaphragm by the object being measured is detected. The electronic auscultation device according to claim 1, characterized in that it corrects the sound data based on the latest reference value determined before the pressure on the diaphragm by the object being measured is detected.

7. The electronic auscultation device according to claim 1, characterized in that the correction means does not determine the reference value while the pressure on the diaphragm by the object being measured is detected.

8. The vibration detection means is A light-reflecting portion is provided on the surface of the diaphragm opposite to the contact surface that contacts the object to be measured, Light source and A light-receiving element having a light-receiving surface that receives light emitted from the light source and specularly reflected by the light-reflecting part, and generating a signal corresponding to the light that reaches the light-receiving surface, The electronic auscultation device according to claim 1, further comprising a signal processing unit that generates a signal corresponding to the vibration of the diaphragm based on the signal generated by the light-receiving element.

9. The electronic auscultation device according to claim 8, characterized in that the pressure detection means detects the pressure applied to the diaphragm by the object to be measured based on the signal generated by the light-receiving element.

10. The electronic auscultation device according to claim 1, further comprising output means for outputting the sound data to an external device.

Images