JP4373191B2 - Portable stethoscope - Google Patents

Description

  The present invention relates to a portable stethoscope that can be mounted on a patient's body and moved.

  2. Description of the Related Art Conventionally, a stethoscope that incorporates a microphone in a stethoscope and listens to heart sounds and the like with the microphone is known (see, for example, Patent Document 1). In addition, a stethoscope is known in which only a hearing part with a built-in microphone is attached to a patient's body for examination (see, for example, Patent Document 2). Then, the patient's condition is grasped by reproducing the sound collected by the microphone using a speaker or the like.

JP-T 8-506495 Japanese Utility Model Publication No. 61-203008

  However, it is difficult to separate vital signs such as heart sounds and breathing sounds from the voice signal because the frequency band is the same, and such a stethoscope always monitors heart sounds and breathing sounds. Has a disadvantage in terms of privacy protection because it also detects voice. In addition, since doctors and others finally listen to the voice to judge the patient's condition, it is unsuitable for urgent things such as childhood asthma attack monitoring.

Stethoscope according to the invention of claim 1 is provided on a single semiconductor substrate, a plurality of condenser microphone elements having different detection frequencies each other to select one of a plurality of condenser microphone element as a detection element And a selection unit.
The stethoscope according to claim 2 is the stethoscope according to claim 1, wherein each of the plurality of condenser microphone elements includes a vibration surface that vibrates at a resonance frequency corresponding to a detection frequency, and each of the vibration surfaces includes: It is provided on a predetermined virtual plane.
The stethoscope according to claim 3 is the stethoscope according to claim 1, wherein each of the plurality of condenser microphone elements includes a vibration surface that vibrates at a resonance frequency corresponding to the detection frequency, and each of the vibration surfaces includes: It is provided on one side of the semiconductor substrate.
The stethoscope according to claim 4 is the stethoscope according to claim 1, wherein each of the plurality of condenser microphone elements is connected to the cantilever and is connected to the cantilever and vibrates at a resonance frequency corresponding to the detection frequency. And a diaphragm having a vibrating surface.
The stethoscope according to claim 5 is the stethoscope according to claim 1, wherein each of the plurality of condenser microphone elements is formed on a vibration surface that is formed on a semiconductor substrate and vibrates by sound pressure, and on the vibration surface. A first electrode and a second electrode fixedly provided with a gap at a position facing the vibration surface on the semiconductor substrate, and the resonance frequency of the vibration surface of the capacitor microphone element is set according to the detection frequency. It is characterized by setting each.
The stethoscope according to claim 6 is the stethoscope according to any one of claims 1 to 5, further comprising: a transmission unit that FM-modulates and transmits a signal detected by the detection element. And

According to the present invention, on a single semiconductor substrate, and a plurality of different condenser microphone elements having the detected frequency to each other, by selecting one as the detection element, different heart sound of detection frequency for the audio signal And vital signs such as breathing sounds can be easily separated, and the desired vital signs can be detected with high sensitivity.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a schematic configuration of a stethoscope according to the present invention. A microphone element 3, a circuit unit 4 and a battery 5 are provided on the base 2 of the stethoscope 1, and these are covered with a casing 6. As will be described later, the microphone element 3 is formed on a Si substrate by a micromachining technique, and has a size of about several mm to 10 mm square.

  The microphone element 3 is a condenser microphone, and one electrode of the capacitor is used as a movable electrode, and the movable electrode is provided on a diaphragm that vibrates by sound pressure. The microphone element 3 has a diaphragm, which will be described later. The microphone element 3 is fixed to the base 2 so that the diaphragm is exposed in the sound cavity 2 a formed in the base 2. The lower surface of the base 2 is brought into contact with the patient's hearing part (for example, chest), and the stethoscope 1 is fixed with an adhesive tape or the like. FIG. 2 is a circuit diagram of the stethoscope 1, and the circuit unit 4 is provided with an FM modulation circuit 40 and an RF amplification circuit 41.

  The microphone element 3 constitutes a capacitor of the LC oscillation circuit, and the capacitance of the capacitor changes when the diaphragm of the microphone element 3 is displaced by the sound pressure. The fundamental oscillation frequency is FM-modulated by the change in the capacitor capacity, and the signal is amplified by the RF amplifier circuit 41 and transmitted to the receiver / transmitter 8 by the antenna 7. The transmitter / receiver 8 performs a voice main power and various determinations based on the received signal, and transmits a signal for turning on and off the power supply of the stethoscope 1.

  Next, a method for manufacturing the microphone element 3 will be described. FIG. 3 is a perspective view showing the entire microphone element 3. The microphone element 3 includes an electrode substrate 3A on which a movable electrode 317a (see FIG. 6C described later) is formed, and a fixed electrode 3B fixed on the electrode substrate 3A so as to face the movable electrode 317a. First, the method for forming the electrode substrate 3A will be described.

First, an SOI (Silicon On Insulator) substrate 31 as shown in FIG. 4A is prepared, and a protective resist 310 is applied to the surface and baked at 90.degree. The substrate 31 has an Si layer 311 (2 μm), an SiO ₂ layer 312 (1 μm), and an Si layer 313 (500 μm) in order from the top, and a protective resist 310 is applied to the surface of the Si layer 311.

  Next, an Al layer 314 is formed on the surface of the Si layer 313 (the back surface of the substrate 31) by sputtering (see FIG. 4B). The Al layer 314 is used as a mask when the Si layer 313 is etched by ICP-RIE (inductively coupled plasma reactive ion etching). A resist is applied to the surface of the Al layer 314, and a square pattern for a diaphragm is formed on the resist 315 by photolithography (see FIG. 4C).

  Using this resist 315 as a mask, the Al layer 314 is etched with a mixed acid P solution to expose the Si layer 313. Thereafter, using the Al layer 314 as a mask, the Si layer 313 is etched by ICP-RIE. In this etching process, the Si layer 313 having a thickness of 500 μm is etched to about 460 μm (see FIG. 4D). At that time, the resist 315 on the Al layer 314 is also removed by etching.

The Si layer 313 having a thickness of about 40 μm remaining in the step of FIG. 4D is then removed by etching by RIE. In the step of FIG. 5A, an O ₂ ashing process by RIE is performed to remove the resist 310 on the Si layer 311, and then the SiO ₂ layer 312 is etched by BHF (ammonium fluoride).

In the step of FIG. 5B, after forming a SiO ₂ layer 316 having a thickness of 0.15 μm on the surface of the Si layer 311 by sputtering, an Au layer 317 having a thickness of 0.1 μm is formed thereon by sputtering. To do. Then, a resist is applied to the surface of the Au layer 317 to form a resist pattern 318 as shown in FIG. Note that before the Au layer 317 is formed, the Al layer 314 is removed with phosphoric acid (or a mixed solution of phosphoric acid, nitric acid, acetic acid, and water).

  The resist pattern 318 is composed of the following three parts. This will be described with reference to FIG. One is a square pattern 318a formed on the diaphragm portion D of the Si layer 311 and having the same shape as the diaphragm portion D, the second is a rectangular pattern 318b corresponding to the terminal portion, and the third is a pattern 318a. And a pattern 318c connecting the pattern 318b.

  Next, in FIG. 5C, the Au layer 317 is etched with potassium iodide using the resist pattern 318 as a mask. As a result, an Au layer (Au pattern) 317 having the same shape as the resist pattern 318 shown in FIG. 7 is formed on the diaphragm portion D. Then, after removing the resist pattern 318 by acetone washing and ethanol washing, polyimide is applied to the surface on which the Au layer 317 is formed and baked. As a result, as shown in FIG. 5D, a 4 μm-thick polyimide layer 319 covering the Au layer 317 is formed.

  6A, a resist 320 is applied on the polyimide layer 319, and the resist 320 is exposed to ultraviolet rays using a mask having the same shape as the resist pattern 318 shown in FIG. As a result, only the portion 320a covering the upper part of the Au layer 317 in the resist 320 is not exposed to ultraviolet rays, so that only the portion of the resist 320 is removed during development (see FIG. 6B). . Further, the polyimide layer 319 where the resist 320 has been removed, that is, the polyimide layer 319 on the Au layer 317 is etched during development, and the Au layer 317 is exposed.

  Thereafter, by removing the resist 320, the electrode substrate 3A on which the movable electrode is formed is formed. FIG. 6C is a perspective view of the electrode substrate 3A. A hole having the same shape as the resist pattern 318 shown in FIG. 7 is formed in the polyimide layer 319, and the Au layer 317 is exposed. In the Au layer 317, a portion indicated by reference numeral 317a is a movable electrode, 317b is a terminal portion, and 317c is a lead portion for connecting them. Only the movable electrode 317a in the Au layer 317 is formed on the diaphragm portion D in FIG.

  Next, a method for forming the fixed electrode 3B will be described. First, as shown in FIG. 8A, an Al layer 131 having a thickness of 0.1 μm is formed on Si 130 by sputtering. The Al layer 131 is used as a mask when the Si 130 is etched by ICP-RIE (inductively coupled plasma reactive ion etching).

  In the step shown in FIG. 8B, a resist is applied on the Al layer 131, and a resist pattern 132 is formed by photolithography. FIG. 8C is a view of the Si 130 of FIG. 8B as viewed from above. The resist pattern 132 is formed in the same shape as the outer ring shape of the fixed electrode 3B shown in FIG. In addition, FIG.8 (b) shows the II-II cross section of FIG.8 (c).

  8D, using the resist pattern 132 as a mask, the Al layer 131 is etched with a mixed acid P solution to expose the Si 130, and the resist pattern 132 is removed by acetone cleaning and ethanol cleaning. As a result, an Al pattern having the same shape as the resist pattern 132 shown in FIG. 8C is formed on the Si 130 by the Al layer 131.

  In the step shown in FIG. 9A, a resist 134 is applied to the surface of the Si 130 so as to cover the Al layer 131, and the resist 134 is exposed and developed using a mask 133 having a hole 133a. FIG. 9B is a plan view showing the resist 134 after development. In the resist 134, a hole pattern corresponding to the hole 133 a in FIG. 9A is formed in a region covering the square region 131 a of the Al layer 131. As shown in FIG. 11, in the Al layer 131, a portion denoted by reference numeral 131b corresponds to a terminal portion 130b of a fixed electrode 3B described later, and a portion denoted by reference numeral 131c corresponds to a lead portion 130c.

  Next, the Al layer 131 is etched with a mixed acid P solution using the resist 134 as a mask, and then the resist 134 is removed with ethanol and acetone (see FIG. 9C). By the etching described above, a plurality of hole patterns 131d are formed in the square region 131a of the Al layer 131.

In the step shown in FIG. 9D, the Si substrate 130 is etched by ICP-RIE using the Al layer 131 as a mask. The etching depth is 360 μm to 370 μm. Thereafter, the Al layer 131 used as a mask is removed with the mixed acid P solution, and then the Si 130 is oxidized by wet oxidation to form a SiO ₂ layer 135 having a thickness of 0.2 μm on the surface of the Si 130 (FIG. 10A). reference).

Then, applying a resist 136 for protection on the surface side of the Si130 which the SiO ₂ layer 135 is formed (shown upper surface), the SiO ₂ layer 135 on the back side (shown lower side) is etched by RIE to remove (See FIG. 10B). Thereafter, after cleaning with hydrofluoric acid, Si 130 is etched with TMAH (tetramethylammonium hydroxide) until SiO ₂ layer 135 appears on the back side as shown in FIG.

When the Si 130 is etched, the resist 136 is removed with sulfuric acid / hydrogen peroxide, and the SiO ₂ layer 135 is removed with BHF (ammonium fluoride) (see FIG. 10D). Thereafter, as shown in FIG. 10E, an Al layer 137 is formed on both the front and back surfaces of the Si 130 by sputtering. As a result, a fixed electrode 3B as shown in FIG. 11 is formed. In the fixed electrode 3B of FIG. 11, 130a is an electrode portion, 130b is a terminal portion, 130c is a lead portion, and 130d is a fixed portion.

  Finally, the microphone element 3 is formed by attaching the fixed electrode 3B to the surface of the polyimide layer 319 of the electrode substrate 3A shown in FIG. 6C with an epoxy resin or the like. At that time, as shown in FIG. 3, the electrode part 130a of the fixed electrode 3B is disposed so as to face the movable electrode 317a of the electrode substrate 3A, and the terminal part 130b, the lead part 130c, and the fixed part 130d are fixed to the polyimide layer 318.

  The polyimide layer 318 functions as a spacer that sets a gap dimension between the movable electrode 317a and the electrode portion 130a. The movable electrode 317a and the electrode portion 130a constitute a capacitor, and the air gap between them is electrically the distance between the electrodes of the capacitor. Since a plurality of through holes 130e are formed in the electrode portion 130a, the capacitor capacity is considered by subtracting the area occupied by the through holes 130e.

In the capacitor-type microphone element 3 shown in FIG. 3, the resonance frequency fs of the diaphragm portion D that is a vibrating membrane is given by the following equation (1).
fs = (λπ / 2a2) · √ (G / μ) (1)
In Expression (1), a is the length of one side of the square diaphragm portion D, and μ is the area density of the diaphragm portion D. λ is a natural frequency coefficient. In the lowest-order vibration mode, the value is 3.646 when the square plate has four sides fixed. G is the bending rigidity of the diaphragm portion D, and is determined by the Young's modulus, Poisson's ratio, and thickness of the member forming the diaphragm portion D.

  From equation (1), it can be seen that the resonance frequency fs is inversely proportional to the square of the length a of one side of the diaphragm portion D, that is, the area. Further, the Q value representing the sharpness of the resonance characteristics increases as the mass of the diaphragm portion D and the spring constant increase. Then, by adjusting these numerical values, the microphone element 3 having desired characteristics (resonance frequency fs, peak size, etc.) can be formed.

  Table 1 shown below shows the objects to be measured by the microphone element 3 and their frequency bands.

心音の場合は周波数帯域は５０Ｈｚ〜５００Ｈｚとなり、特に心室収縮時の房室弁は８０Ｈｚ前後となる。一方、呼吸音は１４０Ｈｚ前後に鋭いピークを有している。

In the case of heart sounds, the frequency band is 50 Hz to 500 Hz, and particularly the atrioventricular valve during ventricular contraction is around 80 Hz. On the other hand, the breathing sound has a sharp peak around 140 Hz.

  Since the detection frequency band of the microphone element 3 is very narrow, since only a part of the frequency band is detected for the conversation voice, it cannot be recognized as the voice of the conversation. Therefore, for example, the resonance frequency fs may be set near fs = 100 Hz for heart sounds, and fs = 140 Hz may be set for breathing sounds. By setting in such a manner, it is possible to listen to a heart sound or a breathing sound.

  In the case of monitoring an asthma attack of an asthma patient, if the resonance frequency fs of the microphone element 3 is set to 400 Hz to 800 Hz, the occurrence of an asthma attack can be detected by detecting a sudden increase in the output value. It becomes possible. Depending on the set value of the resonance frequency fs, a pattern in which the frequency component of asthma appears in the breathing sound is obtained. In such a case, the time series analysis of the frequency is performed using the wavelet transform, and the frequency of the breathing sound or asthma sound is obtained. What is necessary is just to extract a component softly.

  In the above-described embodiment, only one microphone element 3 is provided in the stethoscope 1. However, a plurality of microphone elements 3 having different resonance frequencies fs are provided on the common electrode substrate 3A, and these are connected by a dip switch or the like. You may make it switch and use. Further, instead of providing a dip switch, an electronic switch composed of an FET or the like may be integrated, and an element may be electrically selected by communication from the transmitter / receiver 8.

  For example, in the case of an auditory sound, a plurality of microphone elements 3 having different frequencies within the frequency band shown in Table 1 are formed on the electrode substrate 3A in consideration of individual differences. The example shown in FIG. 12 is a case where five microphone elements 30A to 30E are formed on a common electrode substrate 3A. The resonance frequencies fs of the microphone elements 30A to 30E are 50 Hz, 100 Hz, 500 Hz, and 1000 Hz in this order. FIG. 13 is a circuit diagram of the condenser microphone elements 30A to 30E, and the detection microphone elements are switched by switching the switches DSW1 to DSW5 on and off. In the example shown in FIG. 13, the microphone element 30A can be used.

  Also, in the case of detecting an asthma attack or a sign of childhood asthma by listening to the breathing sound, individual differences are greater than in the case of heart sounds, so a larger number of microphone elements 3 are built on the electrode substrate 3A. It is preferable to leave. In this case, if an alarm is generated by the transmitter / receiver 8 when the magnitude of the frequency signal corresponding to the seizure or its sign exceeds a threshold value, the seizure can be quickly dealt with. The transmitter / receiver 8 may be installed in a nurse center or the like, or may be carried by a nurse or a doctor. Further, the stethoscope 1 itself may generate a warning sound to notify the surrounding people of the emergency situation.

  In the microphone element 3 described above, the diaphragm type movable electrode 317a is formed on the electrode substrate 3A. However, instead of the diaphragm type movable electrode 317a, the movable electrode is formed on a cantilever type diaphragm 400 as shown in FIG. 401 may be provided. The diaphragm 400 is attached to the tip of a cantilever 402 extending from the electrode substrate 3A, and a desired resonance frequency fs can be obtained by adjusting the length of the cantilever 402. Also in this case, by forming cantilevers 402A, 402B, and 402C having different lengths as shown in FIG. 14B, it is possible to cope with a plurality of resonance frequencies fs.

  In the correspondence between the embodiment described above and the elements of the claims, the electrode formation surfaces of the diaphragm portion D and the diaphragm 400 are vibration surfaces, the movable electrodes 317a and 401 are first electrodes, and the electrode portions 130a are The second electrode, the circuit unit 4 constitutes a transmission unit, and the switches SDW1 to SWD5 constitute selection means. In addition, the present invention is not limited to the above embodiment as long as the characteristics of the present invention are not impaired.

It is sectional drawing which shows schematic structure of the stethoscope 1 by this invention. 1 is a circuit diagram of a stethoscope 1. FIG. FIG. 2 is a perspective view showing the entire microphone element 3. It is a figure which shows the formation procedure of 3 A of electrode substrates, and shows each process to (a)-(d). It is a figure which shows the formation procedure following the procedure of FIG. 4, and shows each process to (a)-(d). It is a figure which shows the formation procedure following the procedure of FIG. 5, (a)-(c) shows each process. 5 is a perspective view showing the shape of a resist pattern 318. FIG. It is a figure which shows the formation procedure of the fixed electrode 3B, and shows each process to (a)-(d). It is a figure which shows the formation procedure following the procedure of FIG. 8, and shows each process to (a)-(d). It is a figure which shows the formation procedure following the procedure of FIG. 10, (a)-(e) shows each process. It is a perspective view which shows the final shape of the fixed electrode 3B. It is a top view of 3 A of electrode substrates in which the five microphone elements 30A-30E were formed. It is a circuit diagram of the part of condenser microphone elements 30A-30E. It is a figure which shows a cantilever type microphone element, (a) is a perspective view of an element, (b) is a figure which shows the case where several cantilever 402A, 402B, 402C is provided.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stethoscope 2 Base 3,30A-30E Microphone element 3A Electrode board 3B Fixed electrode 4 Circuit part 5 Battery 6 Casing 8 Receiver / transmitter 40 FM modulation circuit 317a, 401 Movable electrode 400 Diaphragm 402, 402A, 402B, 402C Cantilever D Diaphragm part

Claims (6)

A plurality of condenser microphone elements provided on a single semiconductor substrate and having different detection frequencies;
A stethoscope comprising selection means for selecting any one of the plurality of condenser microphone elements as a detection element. The stethoscope according to claim 1,
Each of the plurality of condenser microphone elements includes a vibration surface that vibrates at a resonance frequency corresponding to the detection frequency,
Each of the vibration surfaces is provided on a predetermined virtual plane. The stethoscope according to claim 1,
Each of the plurality of condenser microphone elements includes a vibration surface that vibrates at a resonance frequency corresponding to the detection frequency,
Each of the vibration surfaces is provided on one side of the semiconductor substrate. The stethoscope according to claim 1,
Each of the plurality of condenser microphone elements is
A cantilever extending from the substrate;
A stethoscope comprising: a diaphragm connected to the cantilever and having a vibration surface that vibrates at a resonance frequency corresponding to the detection frequency. The stethoscope according to claim 1,
Each of the plurality of condenser microphone elements is formed on the semiconductor substrate and vibrates due to sound pressure,
A first electrode formed on the vibration surface; and a second electrode fixedly provided with a gap at a position facing the vibration surface on the semiconductor substrate;
A stethoscope, wherein a resonance frequency of the vibration surface of the condenser microphone element is set in accordance with the detection frequency. The stethoscope according to any one of claims 1 to 5,
A stethoscope comprising a transmission unit that FM modulates and transmits a signal detected by the detection element.

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