Blood pressure monitor, blood pressure measurement method, and Korotkoff sound detection device

Abstract

To extract a Korotkoff sound from a sound generated from a body part to be measured with a good S / N ratio.SOLUTION: A sphygmomanometer includes a diaphragm 62 arranged to receive pressure of air in an air pipe 37d on one surface 62a as part of a pipe wall of the air pipe 37d connected to a cuff in a fluid-circulation manner, or continued to the pipe wall. The diaphragm 62 blocks the pressure of the air in the air pipe 37d in a compression process or a decompression process, of the cuff and causes a sound of a frequency band of a Korotkoff sound of a sound transmitted through the air in the air pipe 37d from a body part to be measured to be transmitted through the diaphragms 62. A chamber Cm arranged including the diaphragm 62 as part of a peripheral wall is provided on the other surface 62b side opposite to one surface 62a with respect to the diaphragm 62. A sound detection device provided facing the air in the chamber Cm is disposed on a part other than the diaphragm 62 of the peripheral wall of the chamber Cm.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a sphygmomanometer and a blood pressure measurement method, and more specifically to a sphygmomanometer and a blood pressure measurement method that measure blood pressure based on Korotkoff sounds generated at a measurement site. The present invention also relates to a Korotkoff sound detection device included in such a sphygmomanometer, which extracts Korotkoff sounds from sounds generated at the measurement site. Background Art

[0002] Conventionally, as this type of Korotkoff sound detection device (and sphygmomanometer), for example, as disclosed in Fig. 2 of Patent Document 1 (Japanese Unexamined Patent Publication No. Sho 58-180132), there has been known a device that includes: a vibrating membrane (metal membrane) that vibrates with sounds collected from a pressurized cuff wrapped around an upper arm or the like of a human body, and has a mechanical resonance point within the frequency band where Korotkoff sounds exist; and a means for converting the mechanical vibration of the vibrating membrane into an electrical signal. This configuration is understood as a condenser microphone. The document states that noise components other than Korotkoff sounds can be removed by the mechanical resonance characteristics of the vibrating membrane, so that only Korotkoff sounds can be extracted. Prior Art Literature Patent Literature

[0003] Patent Document 1 Japanese Unexamined Patent Publication No. Sho 58-180132 Summary of the Invention Problem to be Solved by the Invention

[0004] However, the sound generated at the site under measurement (broadly defined as a wave propagating through an elastic medium such as air) includes not only Korotkoff sounds (frequency range: approximately 20 Hz to 500 Hz) but also pressure pulse waves (frequency range: approximately several tens of Hz), which are pulse wave oscillations of the arteries passing through the site under measurement. The frequency ranges of the two overlap, and moreover, the amplitude of the pressure pulse wave is larger than that of the Korotkoff sounds. For this reason, in practice, the configuration described in Patent Document 1 has the problem that it is difficult to extract only Korotkoff sounds from the sound generated at the site under measurement.

[0005] Therefore, the object of this invention is to provide a blood pressure monitor and blood pressure measurement method that measure blood pressure based on Korotkoff sounds generated at the site to be measured, which can extract Korotkoff sounds from sounds generated at the site to be measured with a good signal-to-noise ratio (S / N ratio), and thus improve the accuracy of blood pressure measurement. Another object of this invention is to provide a Korotkoff sound detection device that can be included in such a blood pressure monitor and can extract Korotkoff sounds from sounds generated at the site to be measured with a good S / N ratio. [Means for solving the problem]

[0006] To solve the above problems, the blood pressure monitor disclosed herein is: A blood pressure monitor that measures blood pressure based on Korotkoff sounds generated at the site being measured, A pressing cuff configured to be attached to the above-mentioned measurement site, Pump and An air pipe connecting the above-mentioned cuff and the above-mentioned pump in a manner that allows fluid to flow, A pressure control unit that, in order to compress the above-mentioned measurement area, supplies air to the cuff through the air piping using the pump to pressurize it, or discharges the air from the cuff through the air piping to reduce the pressure, The pipe wall of the above air piping toThe device comprises a diaphragm arranged in a series such that it receives the air pressure within the air piping on one side, and the diaphragm is configured to block the air pressure within the air piping during the pressurization or depressurization process of the cuff by the pressure control unit, while allowing sound in the frequency band of the Korotkoff tone, transmitted from the part being measured through the air in the air piping, to pass through the diaphragm. Regarding the diaphragm described above, a chamber is provided on the side opposite to the one side described above, with the diaphragm included as part of the peripheral wall, and sound transmitted through the diaphragm is transmitted to the air occupying the chamber. The above-mentioned chamber is provided with a sound detection device on the peripheral wall other than the diaphragm, facing the air inside the chamber, and the sound detection device receives sound that has passed through the diaphragm via the air occupying the chamber and converts it into an electrical signal. The system includes a blood pressure calculation unit that calculates the blood pressure at the measured site based on the electrical signals described above. It is characterized by the following:

[0007] Here, "one side" and "the other side" of the diaphragm refer to both sides of the diaphragm that have the aforementioned spread.

[0008] The phrase "arranged in conjunction with the pipe wall" of the air piping includes, for example, an arrangement in conjunction with the pipe wall of another pipe branched from the air piping.

[0009] In the blood pressure monitor of this disclosure, with a pressure cuff attached to the area to be measured, the pressure control unit pressurizes the cuff by supplying air through the air pipe using the pump to compress the area to be measured, or depressurizes by releasing air from the cuff through the air pipe. The diaphragm receives the air pressure in the air pipe on one side during the pressurizing or depressurizing process of the cuff by the pressure control unit, thereby blocking the air pressure in the air pipe. On the other hand, the diaphragm allows sound in the frequency band of the Korotkoff tone, which has been transmitted from the area to be measured through the air in the air pipe, to pass through the diaphragm. As a result, the sound that has passed through the diaphragm is transmitted to the air occupying the chamber. The sound detection device receives the sound that has passed through the diaphragm via the air occupying the chamber and converts it into an electrical signal. The blood pressure calculation unit calculates the blood pressure of the area to be measured based on the electrical signal.

[0010] In this blood pressure monitor, the diaphragm blocks the air pressure in the air piping, thus reducing the influence of arterial pulse wave vibrations (frequency range; approximately tens of Hz) from the sound generated at the measurement site. Furthermore, the sound detection device receives the sound that has passed through the diaphragm via the air occupying the chamber; in other words, it receives the sound at a position spaced apart from the diaphragm (which directly receives the pressure wave). Therefore, the influence of the pressure wave can be further reduced. As a result, with this blood pressure monitor, Korotkoff sounds can be extracted from the sound generated at the measurement site with a good signal-to-noise ratio. Therefore, the accuracy of blood pressure measurement can be improved.

[0011] If the chamber is sealed, the diaphragm will bend as the air pressure in the air piping gradually changes during the pressurization or depressurization process of the cuff, causing a change in the air pressure inside the chamber. Such pressure changes in the air inside the chamber are undesirable because, for example, if the sound detection device is a condenser microphone, the microphone's sensitivity will change. Furthermore, since the dynamic range of a condenser microphone needs to correspond to the change in cuff pressure (approximately 0 to 300 mmHg), the resolution of the Korotkoff tone will decrease. This will also negatively affect the durability and reliability of the sound detection device.

[0012] Therefore, in one embodiment of the blood pressure monitor, Pressure relief holes are provided in the portion of the chamber's peripheral wall other than the diaphragm, allowing fluid to flow between the inside and outside of the chamber. These pressure relief holes work to prevent the air pressure inside the chamber from changing from atmospheric pressure. It is characterized by the following:

[0013] In this embodiment of the blood pressure monitor, pressure relief holes are provided in the portion of the peripheral wall of the chamber other than the diaphragm, allowing fluid to flow between the inside and outside of the chamber. Therefore, when the diaphragm flexes as the air pressure in the air piping gradually changes during the pressurization or depressurization process of the cuff, causing the air pressure in the chamber to change, the pressure relief holes work to prevent the air pressure in the chamber from changing from atmospheric pressure. Thus, even if the air pressure in the air piping changes, it is possible to prevent adverse effects on the sensitivity, resolution, durability, and reliability of the sound detection device due to this pressure change (load).

[0014] Furthermore, the sound detection device can employ not only condenser microphones, but also various other types of microphones, such as dynamic microphones and MEMS (Micro Electronics Mechanical System) microphones, increasing the flexibility of microphone selection.

[0015] If the pressure relief hole is a wide opening, noise is likely to enter the chamber from outside the chamber through the wide opening. For this reason, there is a possibility that the S / N ratio of the Korotkoff sounds may decrease.

[0016] Accordingly, in the sphygmomanometer of one embodiment, the pressure relief hole has a shape of an elongated conduit or an elongated groove .

[0017] In the sphygmomanometer of this embodiment, the pressure relief hole has the shape of an elongated conduit or an elongated groove. Accordingly, compared to a case where the pressure relief hole is, for example, a wide opening, noise is less likely to enter the chamber from outside the chamber. Therefore, a decrease in the S / N ratio of the Korotkoff sounds caused by the pressure relief hole can be prevented.

[0018] In the sphygmomanometer of one embodiment, a sound insulating material having air permeability and sound insulating properties is accommodated inside the elongated conduit or the elongated groove .

[0019] Here, as the "sound insulating material having air permeability and sound insulating properties", a porous material such as polyurethane foam is typically mentioned.

[0020] In the sphygmomanometer of this embodiment, the sound insulating material accommodated inside the elongated conduit or the elongated groove has air permeability. Therefore, the function of the pressure relief hole of suppressing a change in the pressure of air inside the chamber from atmospheric pressure is not lost due to the presence of the sound insulating material. In addition, since the sound insulating material has sound insulating properties, noise is less likely to enter the chamber from outside the chamber through the elongated conduit or the elongated groove, compared to a case where only air is present inside the elongated conduit or the elongated groove. Therefore, a decrease in the S / N ratio of the Korotkoff sounds caused by the pressure relief hole can be prevented.

[0021] In the sphygmomanometer of one embodiment, the diaphragm is set to have a natural frequency matching the frequency band of the Korotkoff sound .

[0022] In the sphygmomanometer of this embodiment, the diaphragm is set to have a natural frequency matching the frequency band of the Korotkoff sound. Therefore, the diaphragm can selectively transmit sound having the frequency band of the Korotkoff sound among sounds transmitted from the measurement site through the air in the air pipe. Accordingly, the S / N ratio of the Korotkoff sound can be further improved, and the accuracy of blood pressure measurement can be further enhanced.

[0023] In the sphygmomanometer of one embodiment, the chamber is set to have a resonance frequency matching the frequency band of the Korotkoff sound .

[0024] In the sphygmomanometer of this embodiment, the chamber is set to have a resonance frequency matching the frequency band of the Korotkoff sound. Therefore, the chamber can selectively amplify sound having the frequency band of the Korotkoff sound among sounds transmitted through the diaphragm. Accordingly, the S / N ratio of the Korotkoff sound can be further improved, and the accuracy of blood pressure measurement can be further enhanced.

[0025] In the sphygmomanometer of one embodiment, the diaphragm is made of synthetic resin .

[0026] In the sphygmomanometer of this embodiment, since the diaphragm is made of synthetic resin, it is lighter and easier to process in the manufacturing stage compared to a diaphragm made of metal.

[0027] In the sphygmomanometer of one embodiment, The sound detection device is equipped with a threshold setting unit that sets a threshold for extracting the Korotkoff tone from the electrical signal output by the sound detection device. The blood pressure calculation unit calculates the blood pressure at the site being measured based only on the electrical signals that exceed the threshold. It is characterized by the following:

[0028] In this embodiment of the blood pressure monitor, the threshold setting unit sets a threshold for extracting the Korotkoff tone from the electrical signal output by the sound detection device. The blood pressure calculation unit calculates the blood pressure at the measurement site based only on the electrical signal that exceeds the threshold. Therefore, background noise, for example, can be removed from the electrical signal output by the sound detection device. Consequently, the signal-to-noise ratio of the Korotkoff tone can be further improved, and the accuracy of blood pressure measurement can be further enhanced.

[0029] In another context, the blood pressure measurement method disclosed herein is A blood pressure measurement method that measures blood pressure based on Korotkoff sounds generated at the site being measured using the blood pressure monitor described above, With the above-mentioned pressure cuff attached to the area to be measured, the pressure control unit pressurizes the cuff by supplying air to it through the air piping using the pump, or depressurizes it by releasing the air from the cuff through the air piping. During the pressurization or depressurization process of the cuff by the pressure control unit described above, the diaphragm receives the air pressure in the air piping on one side, thereby blocking the air pressure in the air piping, and also allows sound in the frequency band of the Korotkoff tone, which has been transmitted from the measured area through the air in the air piping, to pass through the diaphragm. As a result, the sound that has passed through the diaphragm is transmitted to the air occupying the chamber. The sound detection device described above receives sound that has passed through the diaphragm via the air occupying the chamber and converts it into an electrical signal. The blood pressure calculation unit calculates the blood pressure at the measurement site based on the electrical signal. It is characterized by the following:

[0030] According to the blood pressure measurement method disclosed herein, Korotkoff sounds can be extracted with a good signal-to-noise ratio from the sounds generated at the site being measured, and therefore the accuracy of blood pressure measurement can be improved.

[0031] In yet another aspect, the Korotkoff sound detection device of this disclosure is A Korotkoff sound detection device included in the blood pressure monitor, which extracts Korotkoff sounds from sounds generated at the measured site, The pipe wall of the above air piping to The device comprises a diaphragm arranged in a series such that it receives the air pressure within the air piping on one side, and the diaphragm is configured to block the air pressure within the air piping during the pressurization or depressurization process of the cuff by the pressure control unit, while allowing sound in the frequency band of the Korotkoff tone, transmitted from the part being measured through the air in the air piping, to pass through the diaphragm. Regarding the diaphragm described above, a chamber is provided on the side opposite to the one side described above, with the diaphragm included as part of the peripheral wall, and sound transmitted through the diaphragm is transmitted to the air occupying the chamber. The chamber is equipped with a sound detection device on the peripheral wall other than the diaphragm, facing the air inside the chamber. The sound detection device receives sound that has passed through the diaphragm via the air inside the chamber and converts it into an electrical signal. It is characterized by the following:

[0032] According to the Korotkoff tone detection device disclosed herein, Korotkoff tones can be extracted with a good signal-to-noise ratio from sounds generated at the site under measurement. [Effects of the Invention]

[0033] As is clear from the above, the blood pressure monitor and blood pressure measurement method of this disclosure can extract Korotkoff sounds from sounds generated at the site under measurement with a good signal-to-noise ratio, and therefore the accuracy of blood pressure measurement can be improved. Furthermore, the Korotkoff sound detection device of this disclosure can extract Korotkoff sounds from sounds generated at the site under measurement with a good signal-to-noise ratio. [Brief explanation of the drawing]

[0034] [Figure 1] This figure shows the block configuration of a blood pressure monitor according to one embodiment of this invention. [Figure 2] Figure 2(A) is a perspective view showing the cross-sectional structure of the Korotkoff sound detection device included in the blood pressure monitor described above. Figure 2(B) is a diagram showing a model for setting the resonant frequency of the chamber included in the Korotkoff sound detection device described above. [Figure 3] Figures 3(A), 3(B), and 3(C) show various configurations of a tubular cavity that forms a pressure-relieving hole allowing fluid to flow between the inside and outside of the chamber, respectively. Figure 3(D) shows the results of a noise reduction verification using the tubular cavity shown in Figure 3(C), where sound-insulating material is housed inside the tubular cavity. [Figure 4] This figure shows the blood pressure cuff of the blood pressure monitor shown above attached to the upper arm, which is the site to be measured. [Figure 5] This diagram shows the flow of blood pressure measurement using the blood pressure monitor described above. [Figure 6] Figures 6(A) and 6(B) schematically illustrate the operation of the Korotkoff sound detection device during blood pressure measurement. [Figure 7] This figure illustrates the sound signal output by the Korotkoff sound detection device in the blood pressure monitor (example) described above. [Figure 8] This figure illustrates the sound signal output by the comparative example Korotkoff tone detection device. [Figure 9] Figures 9(A) and 9(B) show modified examples of the pressure relief holes described above, respectively. [Modes for carrying out the invention]

[0035] The embodiments of this invention will now be described in detail with reference to the drawings.

[0036] (Overall configuration of a blood pressure monitor) Figure 1 shows the block structure of a blood pressure monitor 1 according to one embodiment of the present invention. This blood pressure monitor 1 broadly comprises a pressure cuff (hereinafter simply referred to as "cuff") 20 that is attached around the area to be measured (in this example, the upper arm), and a main body 10 that is connected to the cuff 20 via an air pipe 37 so that fluid can flow through it.

[0037] The cuff 20 comprises a bag 21, which is constructed by facing a long, narrow strip of outer fabric and an inner fabric and sewing (or welding) their edges together. Inside this bag 21 is a fluid bag 22 for compressing the area to be measured.

[0038] The main unit 10 is equipped with a control unit 110, a display unit 50, an operation unit 52, a memory 51, a power supply unit 53, a pressure sensor 31, a pump 32, a valve 33, and a Korotkoff sound detection device 60 for extracting Korotkoff sounds from sounds generated at the part being measured. Furthermore, the main unit 10 is equipped with an A / D conversion circuit 310 for converting the analog output from the pressure sensor 31 into a digital signal, a pump drive circuit 320 for driving the pump 32, a valve drive circuit 330 for driving the valve 33, and an A / D conversion circuit 410 for converting the analog output from the Korotkoff sound detection device 60 into a digital signal. Air pipes 37a, 37b, 37c, and 37d are connected to the pressure sensor 31, pump 32, valve 33, and Korotkoff sound detection device 60 so that fluid can flow through them, respectively. These air pipes 37a, 37b, 37c, and 37d merge into a single air pipe 37 within the main body 10, and this air pipe 37 is connected to the fluid bag 22 in the cuff 20 in a way that allows fluid to flow through it. Hereafter, air pipes 37a, 37b, 37c, and 37d will be collectively referred to as air pipe 37 as appropriate. In addition, the output of the Korotkoff sound detection device 60 is transmitted as an electrical signal, the sound signal Ks, to the A / D conversion circuit 410 via wiring 71.

[0039] In this example, the display unit 50 includes a display and indicators, and displays predetermined information (for example, blood pressure measurement results) according to control signals from the control unit 110.

[0040] The operation unit 52 inputs operation signals to the control unit 110 in accordance with the user's instructions. In this example, the operation unit 52 includes a measurement switch 52A for receiving instructions to start / stop blood pressure measurement, and a memory switch 52B for receiving instructions to retrieve blood pressure measurement result data stored in the memory 51.

[0041] Memory 51, as a storage unit, stores program data for controlling the blood pressure monitor 1, setting data for configuring various functions of the blood pressure monitor 1, and data on blood pressure measurement results. Memory 51 is also used as work memory when the program is executed.

[0042] The control unit 110 includes a CPU (Central Processing Unit) and controls the operation of the entire blood pressure monitor 1. Specifically, the control unit 110 acts as a pressure control unit according to a program for controlling the blood pressure monitor 1 stored in the memory 51, and controls the pump 32 and valve 33 in response to operation signals from the operation unit 52. The control unit 110 also acts as a threshold setting unit and a blood pressure calculation unit, calculating the blood pressure value of the measured site based on the sound signal Ks output by the Korotkoff sound detection device 60, and controlling the display unit 50 and the memory 51. The specific method of blood pressure measurement will be described later.

[0043] The power supply unit 53 supplies power to the control unit 110, pressure sensor 31, pump 32, valve 33, display unit 50, memory 51, A / D conversion circuits 310 and 410, pump drive circuit 320, valve drive circuit 330, and the microphone 40, which will be described later. Power is supplied to the microphone 40 through the wiring 71.

[0044] In this example, the pressure sensor 31 is a piezoresistive pressure sensor that receives the pressure of the cuff 20 (in this example, the fluid bag 22) (referred to as "cuff pressure Pc") through the air piping 37 and outputs an electrical signal value based on the change in electrical resistance due to the piezoresistive effect to the control unit 110 through the A / D conversion circuit 310. The control unit 110 detects the cuff pressure Pc according to the electrical signal value from the pressure sensor 31.

[0045] Pump 32 supplies air to the fluid bag 22 through air piping 37 to pressurize the cuff pressure Pc. Valve 33 is opened and closed to control the cuff pressure Pc by discharging or sealing air in the fluid bag 22 through air piping 37. Pump drive circuit 320 drives pump 32 based on control signals provided by control unit 110. Valve drive circuit 330 opens and closes valve 33 based on control signals provided by control unit 110.

[0046] In this example, the Korotkoff sound detection device 60 generally includes a roughly short cylindrical case 61, a diaphragm 62 provided across the inside of the case 61, a microphone 40 as a sound detection device, and a thin tube 63 that forms a hole for pressure relief.

[0047] Figure 2(A) illustrates the cross-sectional structure of the Korotkoff sound detection device 60. This Korotkoff sound detection device 60 comprises a case 61 including a lower case 61A and an upper case 61B. For ease of understanding, Figure 2(A) shows a longitudinal section obtained by cutting the case 61 in half with a vertical plane. Note that the terms "lower," "upper," "vertical," and later "horizontal" are for explanatory purposes only, and the case 61 can be positioned as a single unit within the body 10 of the blood pressure monitor 1 in any orientation.

[0048] The lower case 61A includes a cylindrical portion 61A1 that fits around the air pipe 37d, a plate portion 61A2 having a roughly rectangular plate shape that extends horizontally from the upper end of the cylindrical portion 61A1, a recess 61A3 provided on the upper surface of the plate portion 61A2 as a circular depression with a flat bottom, and an edge portion 61A4 that bends upward from the end edge of the plate portion 61A2 (the right edge in Figure 2(A)). The cylindrical portion 61A1 is hermetically fitted around the air pipe 37d. The space Cd created by the recess 61A3 on the plate portion 61A2 is in fluid-flowable communication with the air pipe 37d (and therefore the air pipe 37) via the cylindrical portion 61A1. In this example, the horizontal dimension of the plate portion 61A2 is set to approximately 50 mm.

[0049] The upper case 61B includes a substantially rectangular plate portion 61B1 that extends substantially parallel to and opposite the plate portion 61A2 of the lower case 61A, a dome portion 61B2 that rises upward in a circular dome shape from the plate portion 61B1, a cylindrical portion 61B3 that extends upward from the approximate center of the dome portion 61B2, and an edge portion 61B4 that bends downward from the end edge of the plate portion 61B1 (the left edge in Figure 2(A)). In this example, the horizontal dimension of the plate portion 61B1 is set to approximately 50 mm, similar to that of the plate portion 61A2 of the lower case 61A. The horizontal position and dimensions of the dome portion 61B2 substantially coincide with the horizontal position and dimensions of the recess 61A3 of the lower case 61A. In this example, an air pipe 38 is hermetically fitted and inserted into the cylindrical portion 61B3. A microphone 40 is hermetically attached to the upper end of the air pipe 38. In this example, a thin tube 63 is attached in the middle of the air piping 38. Inner periphery of plate portion 61B1 61B1i and the inner edge of the dome section 61B2 61B2i The space Cm created by these elements (which forms the chamber described later) is in fluid-flowable communication with the microphone 40 via the cylindrical section 61B3 and the air piping 38.

[0050] A substantially circular, membrane-like diaphragm 62 is provided between the plate portion 61A2 of the lower case 61A and the plate portion 61B1 of the upper case 61B, traversing the space Cd and the space Cm. In this example, the peripheral edge 62e of the diaphragm 62 is sandwiched between the plate portion 61A2 of the lower case 61A and the plate portion 61B1 of the upper case 61B. As a result, the portion of the diaphragm 62 other than the peripheral edge 62e is able to vibrate vertically, as shown by the arrow Bs in Figure 2(A). The peripheral edge 62e of the diaphragm 62 may be bonded to the plate portion 61A2 of the lower case 61A and / or the plate portion 61B1 of the upper case 61B with an adhesive. In this example, the diaphragm 62 is made of a polyurethane sheet (thickness 0.3 mm) as a synthetic resin. In this example, the effective radius R of the diaphragm 62 (which is substantially equal to the horizontal radius of the spatial dimensions Cd, Cm) is set to R = 16.5 mm. Therefore, this diaphragm 62 is lighter and easier to process during manufacturing compared to one made of metal. In this example, the natural frequency of the diaphragm 62 is set to match the frequency range of Korotkoff tones (approximately 20 Hz to 500 Hz). Therefore, the diaphragm 62 can selectively transmit sounds within the frequency range of Korotkoff tones.

[0051] The edges 61A4 of the lower case 61A and 61B4 of the upper case 61B are provided to facilitate alignment of the lower case 61A and the upper case 61B in a horizontal plane when assembling them. Thanks to these edges 61A4 and 61B4, the recess 61A3 of the lower case 61A and the dome portion 61B2 of the upper case 61B can be easily aligned concentrically.

[0052] In this example, the upper surface 62b of the diaphragm 62, the inner peripheral edge 61B1i of the plate portion 61B1, the inner surface 61B2i of the dome portion 61B2, the cylindrical portion 61B3, and the air piping 38 constitute a chamber (represented by the same symbol as the space Cm for simplicity). In this example, the chamber Cm is set to have a resonant frequency that matches the frequency range of Korotkoff sounds (approximately 20Hz to 500Hz).

[0053] Specifically, Figure 2(B) shows a model of Helmholtz resonance when the cylindrical portion 61B3 of the upper case 61B and the air piping 38 are omitted, and the chamber Cm is directly in fluid-flow communication with the microphone 40. (In this case, the thin tube 63 may be directly attached to the dome portion 61B2 of the upper case 61B, as shown in Figure 1, or may be formed integrally with the dome portion 61B2.) In Figure 2(B), S is the effective area of ​​the diaphragm 62 (the area of ​​the part that actually vibrates, in units of m²). 2 ), V is the internal volume of the chamber Cm (unit: m 3 ), where L represents the equivalent neck length (in m). In this case, the resonant frequency f of the chamber Cm is, according to Helmholtz resonance theory, f=(c / 2π)(S / VL) 1 / 2 …(Eq.1) It is calculated by the following equation, where c represents the speed of sound, and c ≈ 340 m / sec. In this example, based on equation (Eq. 1), the resonant frequency f of chamber Cm is set to match the frequency range of Korotkoff tones (approximately 20 Hz to 500 Hz).

[0054] Therefore, the chamber Cm can selectively amplify sounds that have the frequency band of Korotkoff tones among the sounds that have passed through the diaphragm 62.

[0055] The microphone 40 receives sound that has passed through the diaphragm 62 via the air occupying the chamber Cm and converts it into an electrical signal, the sound signal Ks. The sound signal Ks mainly contains components representing Korotkoff tones. This sound signal Ks is transmitted to the control unit 110 as the output of the Korotkoff tone detection device 60 via wiring 71 and the A / D conversion circuit 410.

[0056] In this example, the tubular tube 63, which forms the pressure relief hole, has a cylindrical outer shape. As shown in Figure 3(A), the tubular tube 63 is provided with a pressure relief hole 63o that allows fluid to flow between the inside and outside of the chamber Cm. In this example, the hole 63o is in the form of a straight, elongated pipe. In this example, the axial dimensions of the tubular tube 63 Li The dimensions are set to a range of several millimeters to several centimeters. Additionally, the inner diameter Di of hole 63o is set to approximately 0.1 mm to several millimeters.

[0057] As the pressure of the air in the air piping 37 (and space Cd) gradually changes during the pressurization or depressurization process of the cuff 20, the diaphragm 62 flexes, and when the pressure of the air in the chamber Cm is about to change, the holes 63o, as shown by the arrow Ai in Figure 3(A), allow air to circulate in and out of the chamber Cm, preventing the pressure of the air in the chamber Cm from changing from atmospheric pressure (ambient pressure) Am. Therefore, even if the pressure of the air in the air piping 37 (and space Cd) changes, it is possible to prevent adverse effects on the sensitivity, resolution, durability, and reliability of the microphone 40 due to this pressure change (load).

[0058] Here, the pressure relief hole 63o is in the form of an elongated pipe. Therefore, compared to the case where the hole 63o is, for example, a wide opening (not shown), it is more difficult for noise sound to enter the chamber Cm from outside the chamber Cm through the hole 63o. Thus, it is possible to prevent the Korotkoff tone from decreasing in signal-to-noise ratio due to the pressure relief hole. Note that in the example of Figure 3(A), the hole 63o is straight, but it is not limited to this. For example, in the narrow tube 63B shown in Figure 3(B), the pressure relief hole 63oB provided inside it is in the form of an elongated pipe that reciprocates in a zigzag pattern. Even in this case, as indicated by the arrow AiB, the hole 63oB circulates air inside and outside the chamber Cm, and works to suppress the change in the air pressure inside the chamber Cm from atmospheric pressure Am. Therefore, even if the air pressure in the air piping 37 (and space Cd) changes, it is possible to prevent adverse effects on the sensitivity, resolution, durability, reliability, etc., of the microphone 40 due to this pressure change (load). Moreover, compared to the example in Figure 3(A), it becomes more difficult for noise to enter the chamber Cm from outside the chamber Cm through the hole 63oB. Therefore, it is possible to further prevent a decrease in the signal-to-noise ratio of the Korotkoff tone due to the pressure relief hole.

[0059] Furthermore, in the tubular tube 63C shown in Figure 3(C), the pressure relief hole 63oC provided inside it is in the form of a straight, elongated pipe. However, inside the hole 63oC, a porous polyurethane foam 64 is housed as a sound-insulating material that has both breathability and sound-insulating properties. This polyurethane foam 64 is breathable, as indicated by the arrow AiC. Therefore, the function of the hole 63oC in suppressing the change in air pressure inside the chamber Cm from atmospheric pressure Am is not lost due to the presence of the polyurethane foam 64. In addition, since the polyurethane foam 64 has sound-insulating properties, noise is less likely to enter the chamber Cm from outside the chamber Cm through the hole 63oC compared to when only air is present inside the hole 63oC. Therefore, the reduction in the S / N ratio of the Korotkoff tone due to the hole 63oC can be further prevented. For example, Figure 3(D) shows the axial dimensions of the tubular tube 63C. LiThis shows the results of a verification of how much noise inside the chamber Cm is reduced by housing polyurethane foam 64 inside the hole 63oC, when the hole diameter is 2 mm and the inner diameter Di of the hole 63oC is approximately 0.2 mm. In this example, before housing the polyurethane foam 64 inside the hole 63oC (before time tx), the background noise level (peak-to-peak) Ap-p inside the chamber Cm was approximately 0.11 V. In contrast, after housing the polyurethane foam 64 inside the hole 63oC (after time tx), the background noise level Ap-p inside the chamber Cm was reduced to approximately 0.02 V. Thus, it was verified that the presence of polyurethane foam 64 can effectively reduce noise inside the chamber Cm.

[0060] (Method of measuring blood pressure) When measuring blood pressure, as shown in Figure 4, the cuff 20 is attached around the user's measurement site (in this example, the upper arm) 90 (note that the inner lining is omitted in Figure 4 for simplicity). An artery 91 is assumed to pass through the measurement site 90. The sound generated at the measurement site 90 includes not only Korotkoff sounds (frequency range; approximately 20Hz to 500Hz) but also pressure pulse waves (frequency range; approximately several tens of Hz) dV, which are pulse wave vibrations of the artery 91 passing through the measurement site 90. The sound generated at the measurement site 90 is transmitted from the space Cc created by the fluid bag 22 through the air piping 37 to the Korotkoff sound detection device 60 (space Cd) inside the main unit 10.

[0061] Figure 5 shows the workflow when a user measures their blood pressure using blood pressure monitor 1.

[0062] With the cuff 20 attached to the area to be measured, when the user instructs the start of measurement using the measurement switch 52A on the operating unit 52 provided on the main unit 10, the control unit 110 performs initialization (step S1 in Figure 5). Specifically, the control unit 110 initializes the processing memory area, turns off (stops) the pump 32, opens the valve 33, and adjusts the pressure sensor 31 to 0 mmHg (setting atmospheric pressure to 0 mmHg). In this initial state, as shown in Figure 6(A), the diaphragm 62 of the Korotkoff sound detection device 60 is in a flat state.

[0063] Next, the control unit 110 acts as a pressure control unit and closes the valve 33 via the valve drive circuit 330 (step S2 in Figure 5), and then turns on (drives) the pump 32 via the pump drive circuit 320 to start pressurizing the cuff 20 (fluid bag 22) (step S3). That is, the control unit 110 supplies air as fluid to the fluid bag 22 in the cuff 20 from the pump 32 through the air pipe 37. At the same time, the pressure sensor 31 receives the cuff pressure Pc through the air pipe 37. Based on the output of the pressure sensor 31, the control unit 110 controls the pressurization rate by the pump 32.

[0064] During this pressurization process, as shown in Figure 6(B), the diaphragm 62 of the Korotkoff sound detection device 60 receives the air pressure in the air piping 37 (particularly air piping 37d) on one side (the side facing space Cd) 62a and bends convexly toward the other side 62b. This blocks the air pressure in the air piping 37. Furthermore, when the air pressure in the chamber Cm is about to change due to the bending of the diaphragm 62, the pressure relief hole 63o of the capillary tube 63, as indicated by the arrow Ai, allows air to circulate between the inside and outside of the chamber Cm, thereby preventing the air pressure in the chamber Cm from changing from atmospheric pressure Am.

[0065] Next, in step S4 of Figure 5, the control unit 110 determines, based on the output of the pressure sensor 31, whether the cuff pressure Pc has reached a predetermined value (predetermined pressure). Here, this predetermined pressure may be set to a value that is sufficiently above the user's expected blood pressure value, for example, 180 mmHg, or it may be set to the user's previously measured blood pressure value plus 40 mmHg. The control unit 110 continues to pressurize until the cuff pressure Pc reaches the predetermined pressure, and when the cuff pressure Pc reaches the predetermined pressure (YES in step S4), it stops the pump 32 (step S5). Subsequently, the control unit 110 gradually opens the valve 33 via the valve drive circuit 330 (step S6). This reduces the cuff pressure Pc at a substantially constant rate.

[0066] During this depressurization process, as shown in Figure 6(B), the diaphragm 62 receives the air pressure in the air pipe 37 on one side 62a, blocking the air pressure in the air pipe 37, and vibrates as indicated by arrow Bs, allowing sound in the frequency band of Korotkoff tones to pass through the diaphragm 62. As a result, the sound that has passed through the diaphragm 62 is transmitted to the air occupying the chamber Cm. The microphone 40 receives the sound that has passed through the diaphragm 62 via the air occupying the chamber Cm, converts it into an electrical signal, which is an audio signal Ks, and outputs it via the wiring 71.

[0067] Here, the diaphragm 62 blocks the air pressure in the air piping 37, thereby reducing the influence of the pressure pulse wave dV, which is the pulse wave oscillation of the artery 91, on the sound generated at the measurement site 90. Moreover, the microphone 40 receives the sound that has passed through the diaphragm 62 via the air occupying the chamber Cm, in other words, it receives it at a position spaced apart from the diaphragm 62 (which directly receives the pressure pulse wave). Therefore, the influence of the pressure pulse wave dV can be further reduced. As a result, noise caused by the pressure pulse wave dV can be removed from the sound generated at the measurement site 90.

[0068] Furthermore, since the diaphragm 62 is set to have a natural frequency that matches the frequency band of the Korotkoff tone, it can selectively transmit sound that has the frequency band of the Korotkoff tone from the sound transmitted from the measurement site 90 through the air in the air pipe 37 (and space Cd). In addition, since the chamber Cm is set to have a resonant frequency that matches the frequency band of the Korotkoff tone, it can selectively amplify sound that has the frequency band of the Korotkoff tone from the sound that has passed through the diaphragm 62. Therefore, the Korotkoff tone can be extracted with a good signal-to-noise ratio.

[0069] During this depressurization process, as shown in step S7 (Korotkov tone extraction process) in Figure 5, the control unit 110 acquires the sound signal Ks output by the Korotkov tone detection device 60 (microphone 40) via the A / D conversion circuit 410, and extracts a signal representing the Korotkov tone (referred to as the "Korotkov tone signal Kc") from the sound signal Ks.

[0070] Specifically, Figure 7 illustrates the sound signal Ks output by the Korotkoff tone detection device 60. The bell-shaped curve in Figure 7 represents the cuff pressure Pc. In this example, the cuff pressure Pc reaches a predetermined pressure of 180 mmHg approximately 17 seconds after the start of pressurization, and the depressurization process begins from that point. In this example, the sound signal Ks contains multiple pulsed Korotkoff tone signals Kc that exceed the background noise level Ap-p (approximately 0.02 V in this example). In this example, the control unit 110 acts as a threshold setting unit and sets a threshold TH (approximately 0.06 V in this example) that exceeds the background noise level Ap-p for the sound signal Ks. The control unit 110 then extracts only the signals from the sound signal Ks that exceed the threshold TH as the Korotkoff tone signals Kc. This allows background noise to be removed from the sound signal Ks. Therefore, the signal-to-noise ratio of the Korotkoff tone can be further improved. Along with this, the control unit 110 controls the memory 51 to store the amplitude of the extracted Korotkov tone signal Kc in association with the time when the Korotkov tone signal Kc was generated.

[0071] Subsequently, in step S8 of Figure 5, the control unit 110 acts as a blood pressure calculation unit and calculates the blood pressure at the measurement site based on the Korotkoff sound signal Kc stored in the memory 51. Specifically, during the decompression process described above, the cuff pressure Pc at the time when the Korotkoff sound signal Kc first appears is determined as the systolic blood pressure (SYS), and the cuff pressure Pc at the time when the Korotkoff sound signal Kc last appears is determined as the diastolic blood pressure (DIA).

[0072] Once the blood pressure values ​​(systolic blood pressure SYS and diastolic blood pressure DIA) have been calculated in this manner (YES in step S9), the control unit 110 acts as a pressure control unit and controls the pump 32 to turn off, open the valve 33, and rapidly expel the air from the cuff 20 (fluid bag 22) (step S10). After this, the control unit 110 controls the display unit 50 to display the calculated blood pressure values ​​and saves them to the memory 51.

[0073] Thus, this blood pressure measurement method allows for the extraction of Korotkoff sounds from the sounds generated at the measurement site 90 with a good signal-to-noise ratio, and therefore improves the accuracy of blood pressure measurement.

[0074] As a comparative example, the inventors fabricated a blood pressure monitor including a Korotkoff sound detection device in accordance with Figure 2 of Patent Document 1 (Japanese Patent Publication No. 58-180132). The parts of the blood pressure monitor other than the Korotkoff sound detection device were configured the same as those in the blood pressure monitor 1 described above. Figure 8 illustrates the sound signal Ks' output by the Korotkoff sound detection device. In this example in Figure 8, the cuff pressure Pc reaches a predetermined pressure of 180 mmHg approximately 17 seconds after the start of pressurization, and the depressurization process begins from that point. In the sound signal Ks' of this comparative example, as can be seen by comparing it with the verification results in Figure 7, the signal corresponding to the Korotkoff sound signal Kc is buried in noise. For this reason, it can be said that in this comparative example, it is difficult to extract only the Korotkoff sound from the sound generated at the measured site.

[0075] During the decompression process described above (steps S6-S9 in Figure 5), the diaphragm 62 of the Korotkoff sound detection device 60 gradually attempts to return from a convexly bent state toward the other surface 62b, as shown in Figure 6(B), to a flat state as shown in Figure 6(A). When this causes the air pressure inside the chamber Cm to change, the pressure-relieving holes 63o in the capillary tube 63, as indicated by the arrow Ai, allow air to circulate between the inside and outside of the chamber Cm, thereby preventing the air pressure inside the chamber Cm from changing from atmospheric pressure Am.

[0076] Therefore, not only during the pressurization process (steps S3-S4 in Figure 5) but also during the depressurization process (steps S6-S9 in Figure 5), the change in air pressure within the chamber Cm from atmospheric pressure Am is suppressed. As a result, it is possible to prevent adverse effects on the sensitivity, resolution, durability, and reliability of the microphone 40 due to changes in air pressure (load) within the air piping 37. Furthermore, the microphone 40 can be a variety of types, including not only condenser microphones but also dynamic microphones and MEMS (Micro Electronics Mechanical System) microphones, increasing the freedom of microphone selection.

[0077] (modified version) In the example above, the pressure relief holes 63o, 63oB, and 63oC for the chamber Cm are assumed to be in the form of elongated conduits inside the narrow tubes 63, 63B, and 63C, but are not limited to this. The pressure relief holes may also be in the form of elongated grooves 41d and 61B2d shown in Figure 9(A), or elongated groove 61B1d shown in Figure 9(B). In Figures 9(A) and 9(B), the same reference numerals are used for components corresponding to those already described, and redundant explanations are omitted.

[0078] In the examples of the Korotkoff sound detection devices 60' and 60'' shown in Figures 9(A) and 9(B), the cylindrical portion 61B3 of the upper case 61B and the air piping 38 are omitted compared to the example in Figure 2(A). Instead, a through hole 61B2o is provided at the top of the dome portion 61B2 of the upper case 61B, and a commercially available MEMS microphone 40A with a flattened, roughly rectangular parallelepiped shape is closely attached to the top surface of the dome portion 61B2 via a substrate 41 having a through hole 41o. The chamber Cm is fluidly connected to the microphone 40A via the through-hole 61B2o of the dome portion 61B2 and the through-hole 41o of the substrate 41. Therefore, the microphone 40A can receive sound that has passed through the diaphragm 62 via the air occupying the chamber Cm, convert it into an electrical signal, which is an audio signal Ks, and output it. The dimensions of the microphone 40A in the planar direction (the direction in which it spreads out flat) are several millimeters square.

[0079] In the example of the Korotkoff sound detection device 60' shown in Figure 9(A), the pressure relief holes for the chamber Cm consist of an elongated groove 61B2d formed on the top surface of the dome portion 61B2 of the upper case 61B, and an elongated groove 41d formed on the lower surface of the substrate 41 (the surface in contact with the dome portion 61B2) at a position that overlaps with and corresponds to the elongated groove 61B2d. As the pressure of the air in the air piping 37 (and space Cd) gradually changes during the pressurization or depressurization process of the cuff 20, the diaphragm 62 flexes and the pressure of the air in the chamber Cm is about to change. These elongated grooves 41d, 61B2d work to prevent the pressure of the air in the chamber Cm from changing from atmospheric pressure Am by allowing air to circulate inside and outside the chamber Cm through the through-hole 61B2o of the dome portion 61B2, as shown by the arrow AiD in Figure 9(A). Therefore, even if the air pressure in the air piping 37 (and space Cd) changes, it is possible to prevent adverse effects on the sensitivity, resolution, durability, and reliability of the microphone 40A due to this pressure change (load). Note that one of the elongated grooves 41d and 61B2d may be omitted.

[0080] In the example of the Korotkoff sound detection device 60″ shown in Figure 9(B), the pressure relief hole for the chamber Cm consists of an elongated groove 61B1d formed on the lower surface (the surface in contact with the diaphragm 62) of the plate portion 61B1 of the upper case 61B. As the pressure of the air in the air piping 37 (and space Cd) gradually changes during the pressurization or depressurization process of the cuff 20, the diaphragm 62 flexes, and the pressure of the air in the chamber Cm begins to change. As indicated by the arrow AiE in Figure 9(B), this elongated groove 61B1d allows air to circulate inside and outside the chamber Cm, preventing the pressure of the air in the chamber Cm from changing from atmospheric pressure Am. Therefore, even if the pressure of the air in the air piping 37 (and space Cd) changes, it is possible to prevent adverse effects on the sensitivity, resolution, durability, and reliability of the microphone 40A due to this pressure change (load).

[0081] Furthermore, the elongated grooves 41d and 61B2d shown in Figure 9(A) and the elongated groove 61B1d shown in Figure 9(B) may be filled with a sound-insulating material (for example, polyurethane foam) that has both breathability and sound-insulating properties. This prevents the signal-to-noise ratio of the Korotkoff tone from decreasing due to the elongated grooves 41d, 61B2d, or 61B1d.

[0082] Furthermore, blood pressure measurement using blood pressure monitor 1 may be performed during the pressurization process rather than the depressurization process.

[0083] Furthermore, the measurement site is not limited to the upper arm; it may also be other upper limbs such as the wrist, or lower limbs such as the ankle.

[0084] The embodiments described above are illustrative, and various modifications are possible without departing from the scope of this invention. Each of the above embodiments can stand on its own, but they can also be combined. Furthermore, various features within different embodiments can stand on their own, but they can also be combined. [Explanation of Symbols]

[0085] 1. Blood pressure monitor 10 Main unit 20 Cuffs 22 Fluid bag 31 Pressure Sensor 32 pumps 33 valves 40, 40A Microphone 41 circuit boards 41d, 61B1d, 61B2d: Elongated grooves 60,60′,60″ Korotkoff tone detection device 62 diaphragm 63,63A,63B,63C tubule 63°, 63°B, 63°C: Pressure relief holes 64 Polyurethane foam

Claims

1. A blood pressure monitor that measures blood pressure based on Korotkoff sounds generated at the site being measured, A pressing cuff configured to be attached to the above-mentioned measurement site, Pump and An air pipe connecting the above-mentioned cuff and the above-mentioned pump in a manner that allows fluid to flow, A pressure control unit that, in order to compress the above-mentioned measurement area, supplies air to the cuff through the air piping using the above-mentioned pump to pressurize it, or discharges the air from the cuff through the air piping to reduce the pressure, The above-mentioned air piping is provided with a diaphragm connected to the pipe wall and positioned so as to receive the air pressure inside the air piping on one side, wherein the diaphragm is configured to block the air pressure inside the air piping during the pressurization or depressurization process of the cuff by the pressure control unit, while allowing sound in the frequency band of the Korotkoff tone, transmitted from the part being measured through the air inside the air piping, to pass through the diaphragm. Regarding the diaphragm described above, a chamber is provided on the side opposite to the one side described above, with the diaphragm included as part of the peripheral wall, and sound transmitted through the diaphragm is transmitted to the air occupying the chamber. The above-mentioned chamber is provided with a sound detection device on the peripheral wall other than the diaphragm, facing the air inside the chamber, and the sound detection device receives sound that has passed through the diaphragm via the air occupying the chamber and converts it into an electrical signal. The system includes a blood pressure calculation unit that calculates the blood pressure at the measured site based on the electrical signals described above. A blood pressure monitor characterized by the following features.

2. In the blood pressure monitor according to claim 1, Pressure relief holes are provided in the portion of the chamber's peripheral wall other than the diaphragm, allowing fluid to flow between the inside and outside of the chamber. These pressure relief holes work to prevent the air pressure inside the chamber from changing from atmospheric pressure. A blood pressure monitor characterized by the following features.

3. In the blood pressure monitor according to claim 2, The pressure relief holes described above have the form of elongated pipes or elongated grooves. A blood pressure monitor characterized by the following features.

4. In the blood pressure monitor according to claim 3, A sound-insulating material having both breathability and sound-insulating properties is housed inside the above-mentioned elongated conduit or groove. A blood pressure monitor characterized by the following features.

5. In a blood pressure monitor according to any one of claims 1 to 4, The diaphragm described above is set to have a natural frequency that matches the frequency band of the Korotkoff tone described above. A blood pressure monitor characterized by the following features.

6. In a blood pressure monitor according to any one of claims 1 to 4, The above-mentioned chamber is set to have a resonant frequency that matches the frequency band of the Korotkoff tone. A blood pressure monitor characterized by the following features.

7. In a blood pressure monitor according to any one of claims 1 to 4, The diaphragm mentioned above is made of synthetic resin. A blood pressure monitor characterized by the following features.

8. In a blood pressure monitor according to any one of claims 1 to 4, The sound detection device is equipped with a threshold setting unit that sets a threshold for extracting the Korotkoff tone from the electrical signal output by the sound detection device. The blood pressure calculation unit calculates the blood pressure at the site being measured based only on the electrical signals that exceed the threshold. A blood pressure monitor characterized by the following features.

9. A blood pressure measurement method for measuring blood pressure based on Korotkoff sounds generated at the site to be measured using the blood pressure monitor described in claim 1, With the above-mentioned pressure cuff attached to the area to be measured, the pressure control unit pressurizes the cuff by supplying air to it through the air piping using the pump, or depressurizes it by releasing the air from the cuff through the air piping. During the pressurization or depressurization process of the cuff by the pressure control unit described above, the diaphragm receives the air pressure in the air piping on one side, thereby blocking the air pressure in the air piping, and also allows sound in the frequency band of the Korotkoff tone, which has been transmitted from the measured area through the air in the air piping, to pass through the diaphragm. As a result, the sound that has passed through the diaphragm is transmitted to the air occupying the chamber. The sound detection device described above receives sound that has passed through the diaphragm via the air occupying the chamber and converts it into an electrical signal. The blood pressure calculation unit calculates the blood pressure at the measurement site based on the electrical signal. A blood pressure measurement method characterized by the following features.

10. A Korotkoff sound detection device included in the blood pressure monitor described in claim 1, which extracts Korotkoff sounds from sounds generated at the site to be measured, The above-mentioned air piping is provided with a diaphragm connected to the pipe wall and positioned so as to receive the air pressure inside the air piping on one side, wherein the diaphragm is configured to block the air pressure inside the air piping during the pressurization or depressurization process of the cuff by the pressure control unit, while allowing sound in the frequency band of the Korotkoff tone, transmitted from the part being measured through the air inside the air piping, to pass through the diaphragm. Regarding the diaphragm described above, a chamber is provided on the side opposite to the one side described above, with the diaphragm included as part of the peripheral wall, and sound transmitted through the diaphragm is transmitted to the air occupying the chamber. The chamber is equipped with a sound detection device on the peripheral wall other than the diaphragm, facing the air inside the chamber. The sound detection device receives sound that has passed through the diaphragm via the air inside the chamber and converts it into an electrical signal. A Korotkoff sound detection device characterized by the following features.

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