Piezoelectric microphone system and abnormality detection method

Abstract

To provide a piezoelectric microphone system capable of acquiring information of a living body or the like by using a piezoelectric microphone having a configuration similar to that of a piezoelectric sensor.SOLUTION: The piezoelectric microphone 3 is a microphone that converts vibration into an electric signal by a piezoelectric effect. The piezoelectric microphone 3 is fixed to the surface of a living body. The signal receiving device 9 receives an electric signal obtained by converting the heart sound and / or the lung sound by the piezoelectric microphone 3. The abnormality detection unit 13 determines whether or not the electric signal received by the signal receiving device 9 from the piezoelectric microphone 3 includes a portion generated by a sound generated due to occurrence of an abnormality in the sound source 15.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a piezoelectric microphone system and an abnormality detection method, and more particularly to a piezoelectric microphone system using a piezoelectric microphone. [Background technology]

[0002] Figures 12(a) and (b) show the results of frequency analysis of recorded sounds when the long-term average spectrum of speech recorded with a commercially available pin microphone and a pharyngeal microphone was analyzed to examine the frequency characteristics of the microphones.

[0003] Patent Document 1 discloses an example of a piezoelectric microphone. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-56351 Summary of the Invention [Problem to be solved by the invention]

[0005] However, commonly used pin microphones are attached to clothing, and pharyngeal microphones are worn around the neck and pick up vibrations near the Adam's apple, making it impossible to capture heart sounds, lung sounds, etc.

[0006] Patent Document 1 describes a piezoelectric microphone, but does not describe how to utilize the piezoelectric microphone.

[0007] The inventors are conducting research and development of a flexible ultrasonic / piezoelectric sensor using a porous piezoelectric film made of a sol-gel composite.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a piezoelectric microphone system that is capable of determining abnormalities in a sound source using a piezoelectric microphone having a configuration similar to that of a piezoelectric sensor. [Means for solving the problem]

[0009] A first aspect of the present invention is a piezoelectric microphone system comprising a piezoelectric microphone and a signal processing device, the signal processing device comprising a signal receiving device and an abnormality detection unit, the piezoelectric microphone being a microphone that converts vibrations into an electrical signal by the piezoelectric effect, the piezoelectric microphone being fixed to the surface of a living body with one of its electrodes located between a substrate and the living body, the signal receiving device receiving an electrical signal obtained by the piezoelectric microphone converting heart sounds and / or lung sounds, and the abnormality detection unit determining whether the electrical signal received by the signal receiving device from the piezoelectric microphone is a converted sound generated from a sound source in which an abnormality is occurring.

[0010] A second aspect of the present invention is the piezoelectric microphone system of the first aspect, wherein the resonance point of the piezoelectric microphone is equal to or greater than 30 Hz and equal to or less than 1500 Hz.

[0011] A third aspect of the present invention is a piezoelectric microphone system according to the first or second aspect, wherein the resonance point of the piezoelectric microphone is between 30 Hz and 800 Hz, and the piezoelectric microphone simultaneously captures heart sounds and lung sounds and converts them into electrical signals.

[0012] A fourth aspect of the present invention is a method for detecting an abnormality in a piezoelectric microphone system, the method comprising: the piezoelectric microphone system including a piezoelectric microphone and a signal processing device; the signal processing device including a signal receiving device and an abnormality detection unit; the piezoelectric microphone converting vibrations into an electrical signal by the piezoelectric effect; the piezoelectric microphone being fixed to the surface of a living body with one of its electrodes located between a substrate and the living body; the signal receiving device receiving an electrical signal obtained by the piezoelectric microphone converting heart sounds and / or lung sounds; and the abnormality detection unit determining whether the electrical signal received from the piezoelectric microphone by the signal receiving device is a converted sound generated from a sound source in which an abnormality is occurring.

[0013] A fifth aspect of the present invention is the abnormality detection method according to the fourth aspect, wherein the resonance point of the piezoelectric microphone is equal to or higher than 30 Hz and equal to or lower than 1500 Hz.

[0014] A sixth aspect of the present invention is the abnormality detection method of the fourth or fifth aspect, wherein the resonance point of the piezoelectric microphone is between 30 Hz and 800 Hz, and the piezoelectric microphone simultaneously acquires heart sounds and lung sounds and converts them into electrical signals.

[0015] A seventh aspect of the present invention is a program for causing a computer to function as the anomaly detection unit of any one of the first to third aspects. The present invention may also be understood as a computer-readable recording medium on which the program of the seventh aspect is recorded. [Effects of the Invention]

[0016] According to the present invention, a piezoelectric microphone can be used to acquire heart sounds, lung sounds, etc., and determine whether or not there is an abnormality in these sounds. Here, the piezoelectric microphone can be realized by, for example, a piezoelectric unimorph microphone having a structure similar to that of a flexible piezoelectric sensor. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram showing an example of the configuration of a piezoelectric microphone system according to an embodiment of the present invention; [Figure 2] 1A to 1C are diagrams illustrating an example of a process for producing a PZT / PZT piezoelectric film. [Figure 3] 2A to 2C are diagrams illustrating the configuration of porous piezoelectric ceramics in the piezoelectric microphone 3. [Figure 4] 10 is a flowchart showing an example of the operation of the abnormality detection unit 13. FIG. [Figure 5] FIG. 1 is a first diagram for explaining a first prototype of a piezoelectric microphone 3. [Figure 6] FIG. 2 is a second diagram for explaining the first prototype of the piezoelectric microphone 3. [Figure 7] FIG. 1 is a first diagram illustrating a second prototype of the piezoelectric microphone 3. [Figure 8] FIG. 2 is a second diagram for explaining the second prototype of the piezoelectric microphone 3. [Figure 9] 10A and 10B are diagrams for explaining a third prototype of the piezoelectric microphone 3. FIG. [Figure 10] FIG. 10 is a diagram showing the waveform of heart sounds heard using the second prototype. [Figure 11] (a) The shape of the fourth prototype of the piezoelectric microphone, and (b) the waveform of the heart sound picked up by the fourth prototype. [Figure 12] (a) and (b) are figures showing the results of frequency analysis of recorded sounds when the long-term average spectrum of speech recorded with a commercially available pin microphone and a pharyngeal microphone was analyzed to examine the frequency characteristics of the microphones. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments.

[0019] FIG. 1 is a diagram showing an example of the configuration of a piezoelectric microphone system 1 according to an embodiment of the present invention.

[0020] The piezoelectric microphone system 1 includes a piezoelectric microphone 3, a signal line 5, and a signal processing device 7. The signal processing device 7 includes a signal receiving device 9 and a processing device 11. The processing device 11 includes an abnormality detection unit 13.

[0021] The object 17 is a tangible object. The object 17 is a medium that transmits the sound emitted from the sound source 15.

[0022] The piezoelectric microphone 3 is fixed to the surface of the object 17 with one of the electrodes between the substrate and the object 17. In this example, the piezoelectric microphone 3 is attached and fixed to the surface of the object 17 with an adhesive tool 19. The adhesive tool 19 is, for example, a tape, a belt, or a band.

[0023] Piezoelectric microphone 3 is fixed in a state where one of the electrodes vibrates in response to sound emitted from sound source 15. Object 17 may have an insulator or the like that can transmit the sound emitted from sound source 15. Alternatively, for example, one of the electrodes may be in contact with the surface of object 17. In this case, the electrode may be insulated.

[0024] In the following description, the piezoelectric microphone 3 is fixed to the surface of a living body. The sound source 15 is an organ such as the heart or lungs. The piezoelectric microphone 3 vibrates in response to heart sounds and / or lung sounds and converts these vibrations into an electrical signal through the piezoelectric effect. This allows it to function, for example, like a wearable stethoscope. The piezoelectric microphone 3 may be covered with an insulator that can transmit heart sounds and / or lung sounds and fixed to the surface of the living body.

[0025] A sound emitted from a sound source 15 is transmitted to one of the electrodes of the piezoelectric microphone 3. The piezoelectric microphone 3 converts the transmitted sound into an electric signal.

[0026] The piezoelectric microphone 3 converts vibrations into electrical signals through the piezoelectric effect. For example, the diameter of a thin, circular piezoelectric ceramic plate expands and contracts when piezoelectricity is applied to both sides. A unimorph diaphragm, formed by bonding this to a metal plate, bends because the metal plate does not expand and contract. Conversely, when external sound pressure is applied to the unimorph diaphragm, causing it to bend and the piezoelectric ceramic plate to expand and contract, an electric charge is generated on both sides. Similarly, the piezoelectric microphone 3 also has a unimorph diaphragm formed by forming a piezoelectric film on a substrate. External sound pressure causes the diaphragm to bend, which is converted into an electrical signal through the piezoelectric effect of the piezoelectric film. The substrate and piezoelectric film are, for example, rectangular. The piezoelectric microphone 3 can be configured as a piezoelectric unimorph microphone, which has a structure similar to that of a flexible piezoelectric sensor.

[0027] In the prototype described later, a (Pb(Zr,Ti)O3:PZT) / PZT piezoelectric film (referred to as a PZT / PZT piezoelectric film) that is flexible and has relatively good piezoelectric properties was used as the piezoelectric film in the piezoelectric microphone 3. Figure 2 shows an example of the process for creating a PZT / PZT piezoelectric film. A mixture of piezoelectric powder and a sol-gel solution is made in a ball mill. The mixture is spray-coated, dried, and baked repeatedly until the target film thickness is reached, and then a polarization process is performed to create electrodes, thereby creating a PZT / PZT piezoelectric film.

[0028] 3 is a diagram illustrating the configuration of the porous piezoelectric ceramic in the piezoelectric microphone 3. The upper electrode 21 and the rear electrode 23 are respectively located above and below the non-dipolar dielectrics 25. Air bubbles 27 exist in the non-dipolar dielectric 25. Positive and negative charges exist above and below the air bubbles 27, corresponding to the upper electrode 21 and the lower electrode 23, and macro-dipoles 29 exist. In the piezoelectric microphone 3, multiple air bubbles (including the air bubbles 27) vibrate in response to sound, and electrical signals can be obtained after conversion by the upper electrode 21 and the lower electrode 23.

[0029] The signal line 5 is a signal line that connects the piezoelectric microphone 3 to the signal receiving device 9. The signal receiving device 9 receives the electrical signal obtained by the piezoelectric microphone 3 converting sound.

[0030] The abnormality detection unit 13 determines whether the electrical signal received by the signal receiving device 9 is a converted version of a sound generated from a sound source where an abnormality is occurring. The processing device 11 is, for example, a processor. The abnormality detection unit 13 can be realized by, for example, a processor that operates under the control of a program.

[0031] FIG. 4 is a flow chart showing an example of the operation of the abnormality detection unit 13.

[0032] The abnormality detection unit 13 determines whether the signal receiving device 9 has received an electrical signal of a certain reference value or more from the piezoelectric microphone 3 (step STA1). The abnormality detection unit 13 waits until the signal receiving device 9 has received an electrical signal of a certain reference value or more from the piezoelectric microphone 3, and then proceeds to step STA2.

[0033] When an abnormality occurs in sound source 15, a portion of the sound produced differs from that produced in a normal state (when no abnormality occurs). The portion of the sound produced by sound source 15 in an abnormal state that differs from the sound produced by sound source 15 in a normal state is referred to as an "abnormal sound."

[0034] In step STA2, the abnormality detection unit 13 performs processing to detect a portion of the electrical signal received by the signal receiving device 9 from the piezoelectric microphone 3 that is obtained by converting an abnormal sound.

[0035] The abnormality detection unit 13 determines whether or not there is a portion obtained by converting an abnormal sound in the electrical signal received by the signal receiving device 9 from the piezoelectric microphone 3 (step STA3). If there is no portion (YES in step STA3), the sound source 15 is determined to be normal (step STA4) and the process returns to step STA1. If there is a portion (NO in step STA3), the sound source 15 is determined to be abnormal (step STA5) and the process returns to step STA1.

[0036] The anomaly detection unit 13 can be realized by creating a model using, for example, a learning process. For example, annotation data that identifies the presence or absence of an anomaly and the location of the anomaly is added to the electrical signals obtained from the piezoelectric microphone 3 by sounds emitted by sound source 15 when no anomaly exists and sounds emitted by sound source 15 when an anomaly exists, to create training data, and a learning process is performed to generate a model that can identify the presence or absence of an anomaly and the location of the anomaly. The anomaly detection unit 13 can make the judgment of step STA3 by using this model to identify the presence or absence of an anomaly and the location of the anomaly in the electrical signal received by the signal receiving device 9 from the piezoelectric microphone 3.

[0037] 5 and 6 are diagrams for explaining a first prototype of a piezoelectric microphone.

[0038] Figure 5(a) shows the wiring to the electrodes of a piezoelectric microphone. Figure 5(b) is an enlarged view of the piezoelectric microphone in Figure 5(a). The resonant frequency of a piezoelectric microphone is determined by the shape of the substrate. While the substrate length is the primary factor, the device's stiffness and width also affect the frequency response and sound quality. The substrate 31 (SUS304, thickness t = 50 μm) measures 29 mm in length and 16 mm in width. The piezoelectric film 33 (PZT / PZT composite, film thickness 80–100 μm) measures 21 mm in length and 12 mm in width. The electrode 35 (Ag paste, approximately 10 μm thick) measures 18 mm in length and 9 mm in width. The wiring connecting to the upper electrode and ground is taken out from a coaxial cable, the other end of which is connected to a mini-plug terminal that can be directly connected to a recording device. The surface is coated with a waterproof spray as a protective film.

[0039] Figure 6(a) shows a photograph of the first prototype. We also analyzed the long-term average spectrum of the recorded sound to examine the frequency characteristics of the microphone. Figure 6(b) shows the results of frequency analysis of the sound recorded by the first prototype.

[0040] 7 and 8 are diagrams for explaining a second prototype of the piezoelectric microphone.

[0041] Figure 7(a) shows the state of wiring to the electrodes of a piezoelectric microphone. Figure 7(b) is an enlarged view of the piezoelectric microphone portion of Figure 7(a). The substrate 41 (SUS304, thickness t = 50 μm) has a longitudinal length of 29 mm and a transverse length (width) of 8 mm. The piezoelectric film 43 (PZT / PZT composite, film thickness 80-100 μm) has a longitudinal length of 21 mm and a transverse length of 6 mm. The electrode 45 (Ag paste, approximately 10 μm thick) has a longitudinal length of 18 mm and a transverse length of 4 mm. The wiring connecting to the upper electrode and ground is taken out from a coaxial cable, the other end of which is connected to a mini-plug terminal that can be directly connected to a recording device. A waterproof spray is applied to the surface as a protective film.

[0042] Figure 8(a) shows a photograph of the second prototype. We also analyzed the long-term average spectrum of the recorded sound to examine the frequency characteristics of the microphone. Figure 8(b) shows the results of frequency analysis of the sound recorded by the second prototype.

[0043] Comparing Figure 6(b) and Figure 8(b), the peak position in Figure 8(b) is slightly shifted to the high frequency side compared to Figure 6(b). As a result, the peak position is the same as that of a lapel microphone (see Figure 10(a)). It was also confirmed that the resonance is stronger on the high frequency side. It is thought that the narrower width makes it easier for resonance to occur in the longitudinal direction.

[0044] Figure 9(a) is a photograph of the third prototype, and Figure 9(b) shows the prototype attached to the chest of a baby doll with tape.

[0045] When heart and lung sounds obtained from a normal heart and lungs were generated inside a baby-like doll, the third prototype was able to obtain electrical signals from the heart and lung sounds in the absence of any conversational sounds.

[0046] Furthermore, when heart and lung sounds obtained from an abnormal heart and lungs were generated inside a doll modeled after a baby, it was confirmed that the electrical signals obtained by the third prototype were capable of detecting abnormal sounds in the heart and lungs.

[0047] In the piezoelectric microphone system 1 of Figure 1, an example is shown in which the signal receiving device 9 receives the electrical signal of the piezoelectric microphone 3 via a wired connection, but the piezoelectric microphone 3 may also be equipped with a transmitting device that transmits data indicating the electrical signal, and the signal receiving device 9 may receive the data via wireless communication.

[0048] Figures 10 and 11 show the results of an experiment in which the heart sounds of an adult male were listened to using a piezoelectric microphone. The subject lay on his back and a prototype piezoelectric microphone was attached using silicon gel tape to listen to the heart sounds. The recording conditions were a quantization bit of 16 bits, a sampling frequency of 48 kHz, and resampling at 2 kHz.

[0049] Figure 10 shows the waveform of heart sounds heard using the second prototype. The (first) resonance point (the frequency at which the vibration body's resonance reaches its maximum) of the second prototype is 35,000 Hz. The horizontal axis indicates time (seconds), and the vertical axis indicates amplitude. Heart sounds could be heard using the second prototype. The signal-to-noise ratio calculated using equation 1 was 11.6 dB.

[0050]

number

[0051] Figure 11 shows (a) the shape of the fourth prototype of the piezoelectric microphone and (b) the waveform of the heart sound picked up by the fourth prototype. The (first) resonance point of the fourth prototype is 198 Hz. In Figure 11(b), the horizontal axis indicates time (seconds) and the vertical axis indicates amplitude. The heart sound was picked up using the fourth prototype. The signal-to-noise ratio calculated using Equation 1 was 13.8 dB.

[0052] The frequency of heart sounds is approximately between 30 Hz and 1500 Hz. The second prototype was designed to accommodate voice. Therefore, the (first) resonance point of the second prototype was 35,000 Hz, which is greater than the frequency of heart sounds. In contrast, the (first) resonance point of the fourth prototype was 198 Hz, which is within the range of heart sound frequencies. Therefore, by setting the resonance point within the range of heart sound frequencies (i.e., between 30 Hz and 1500 Hz), the signal-to-noise ratio can be increased.

[0053] Furthermore, lung sounds fall within the frequency range of approximately 25 Hz to 800 Hz, so it is believed that the signal-to-noise ratio can be increased by setting the resonance point within the frequency range of lung sounds (i.e., 25 Hz to 800 Hz).

[0054] Therefore, a piezoelectric microphone can detect heart sounds and lung sounds even if its resonance point is outside the frequency range of heart sounds and lung sounds, but by setting the resonance point between 25 Hz and 1500 Hz, it can accurately detect at least one of heart sounds and lung sounds.Furthermore, by setting the resonance point between 30 Hz and 800 Hz, it can accurately detect heart sounds and lung sounds. [Explanation of symbols]

[0055] 1 Piezoelectric microphone system 3 Piezoelectric microphone 5 Signal line 7 Signal Processing Device 9. Signal receiving device 11 Processing equipment 13 Abnormality detection unit 15 sound sources 17 Object 19. Application tools 21 Upper electrode 23 Lower electrode 25 Non-polar dielectrics 27 Bubbles 29 Macrodipole 31 PCB 33 Piezoelectric film 35 electrodes 41 PCB 43 Piezoelectric film 45 electrode

Claims

1. 1. A piezoelectric microphone system comprising: A piezoelectric microphone and a signal processor are provided. the signal processing device includes a signal receiving device and an abnormality detection unit; The piezoelectric microphone converts vibrations into an electric signal by the piezoelectric effect. the piezoelectric microphone is fixed to the surface of the living body with one of the electrodes between the substrate and the living body; the signal receiving device receives an electrical signal obtained by converting heart sounds and / or lung sounds with the piezoelectric microphone; A piezoelectric microphone system in which the abnormality detection unit determines whether the electrical signal received by the signal receiving device from the piezoelectric microphone is a converted sound generated from a sound source in which an abnormality is occurring.

2. 2. The piezoelectric microphone system according to claim 1, wherein the resonance point of the piezoelectric microphone is between 30 Hz and 1500 Hz.

3. The resonance point of the piezoelectric microphone is 30 Hz or more and 800 Hz or less, The piezoelectric microphone system of claim 1 , wherein the piezoelectric microphone simultaneously captures and converts heart and lung sounds into electrical signals.

4. 1. A method for detecting an abnormality in a piezoelectric microphone system, comprising: The piezoelectric microphone system includes a piezoelectric microphone and a signal processing device. the signal processing device includes a signal receiving device and an abnormality detection unit; The piezoelectric microphone converts vibrations into an electric signal by the piezoelectric effect. the piezoelectric microphone is fixed to the surface of the living body with one of the electrodes between the substrate and the living body; The signal receiving device receives an electrical signal obtained by converting heart sounds and / or lung sounds with the piezoelectric microphone; An abnormality detection method including a step in which the abnormality detection unit determines whether the electrical signal received by the signal receiving device from the piezoelectric microphone is a converted sound generated from a sound source in which an abnormality is occurring.

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