A flexible wearable electronic heart sound stethoscope

Abstract

The application discloses a flexible wearable electronic heart sound stethoscope, which comprises a sampler, a preamplifier, an anti-aliasing filter and an analog-to-digital conversion module which are sequentially connected and form a whole, and the sampler is packaged by a flexible material, wherein two silicon microphones are used to collect heart sounds and noise respectively, and the silicon microphone comprises a MEMS analog acoustic sensor which is installed on an FPCB. In the application, the sampler adopts the FPCB circuit board, so that the comfort and the closed sound cavity are achieved, and the subsequent signal processing part adopts the hard PCB circuit board, so that the high integration and the stable signal processing are achieved; the two circuit boards are connected through an interface, so that the sampler is easy to replace, meanwhile, the FPCB part with a relatively low service life can be replaced in time, and the use cost of the flexible electronic heart sound stethoscope is reduced. In addition, through reasonable acoustic structure design, the signal received by the MEMS analog acoustic sensor is relatively large.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of medical electronic equipment, and particularly relates to a flexible wearable electronic heart sound stethoscope. BACKGROUND

[0002] At present, the domestic market mainly focuses on hard electronic stethoscopes, and few electronic stethoscopes are made of flexible materials. The hard electronic stethoscope has the problems of poor wearing comfort and unstable pickup of heart sounds, and is difficult to be applied to wearable auscultation equipment.

[0003] A few studies such as document 1 [Lee SH, Kim YS, Yeo MK, Mahmood M, Zavanelli N, Chung C, Heo JY, Kim Y, Jung SS, Yeo WH. Fully portable continuous real-time auscultation with a soft wearable stethoscope designed for automated disease diagnosis [J]. Science Advances, 2022, 8 (21): eabo5867] propose a design for a flexible electronic stethoscope, but since the signal processing transmission circuit and the acoustic sensor are designed on the same FPCB (Flexible Printed Circuit Board), the cost of this design is too high for a disposable wearable device.

[0004] In addition, there are few studies on the fixing method of the flexible electronic stethoscope on the skin at present. During the use of the flexible electronic heart sound stethoscope, there is no support provided by the hand as in the use of the conventional stethoscope, resulting in a low signal-to-noise ratio of the flexible electronic heart sound stethoscope during auscultation. To this end, a stable support needs to be applied to the flexible electronic heart sound stethoscope to improve the signal-to-noise ratio of the flexible electronic heart sound stethoscope; document 1 supports the flexible electronic stethoscope by using pressure tape and studies the influence of different tapes on the signal-to-noise ratio. This way improves the signal-to-noise ratio during auscultation, but does not fully discuss the mechanism by which the signal-to-noise ratio is improved. After physically modeling the stethoscope system, it can be understood that the flexible electronic stethoscope needs to increase a stable displacement support to ensure that the sensor diaphragm of the stethoscope and the skin have relative movement. At the same time, the device designed in document 1 does not configure a noise reduction mode on the hardware, but only filters through the computer, which may cause some weak key sounds in the heart sound signal to be filtered out.

[0005] A patent search revealed that noise reduction methods used in electronic stethoscopes include algorithmic and hardware noise reduction. Among them, Chinese patent application publication number CN118924323A discloses an electronic stethoscope that uses active noise reduction. It employs a dual-microphone setup: one microphone is used to receive heart sounds, but inevitably picks up noise; the other microphone is specifically designed to receive noise. By differentiating the signals received by the two microphones, a relatively pure heart sound signal can be obtained. This patented technology uses a second sound collector to collect secondary noise data to correct the total sound data collected by the first sound collector. This allows the first noise data to be filtered out from the total sound data collected by the first sound collector, enabling accurate body sound data collection using a low-cost, standard microphone, improving the accuracy of the test results. However, testing revealed that the design of surrounding the first sound collector with sound-absorbing material is unnecessary and may even result in the noise signals collected by the two microphones differing in magnitude at different frequencies, making it difficult to eliminate noise across a wide frequency range through differential analysis. Summary of the Invention

[0006] In view of the above, the present invention provides a flexible wearable electronic heart sound stethoscope that can filter out the noise of the heart sound stethoscope, solve the problems of short service life and high cost when the equipment is designed entirely with FPCB, and is less affected by movement during wearing.

[0007] A flexible, wearable electronic heart sound stethoscope consists of a sampler, a preamplifier, an anti-aliasing filter, and an analog-to-digital conversion module, connected in sequence. The sampler is encapsulated in a flexible material and utilizes two silicon microphones to collect heart sounds and murmurs, respectively. The silicon microphones contain MEMS (Micro-Electro-Mechanical System) analog acoustic sensors mounted on a flexible printed circuit board (FPCB).

[0008] Furthermore, the preamplifier, anti-aliasing filter and analog-to-digital conversion module are mounted on a rigid PCB (Printed Circuit Board).

[0009] Furthermore, one of the two silicon microphones is in contact with the chest skin through a closed sound cavity to collect heart sounds, and the other is in contact with the chest skin through an open sound cavity to collect murmurs.

[0010] Furthermore, the MEMS analog acoustic sensors of the silicon microphones are both set towards the skin; rather than one facing the skin and the other facing the outside, to prevent the two silicon microphones from receiving different noises due to noise reflection on the skin. This setting can filter out as much noise as possible.

[0011] Furthermore, the analog-to-digital conversion module is connected to a Bluetooth transmission module, which can convert the heart sounds into digital signals and upload them to the user's mobile device for viewing.

[0012] Furthermore, the top of the silicon microphone used to collect heart sounds is provided with a support of sufficient rigidity to prevent the silicon microphone from displacing relative to the body as a whole, ensuring relative movement between the MEMS simulated acoustic sensor and the chest skin. The top of the silicon microphone used to collect murmurs does not require a support. When the flexible electronic stethoscope is worn on the body, there is no hand to provide support, so the silicon microphone and the skin cannot be guaranteed to have relative movement. Therefore, the signal received by the silicon microphone is very weak. In the test, it was found that sufficient support is needed to ensure that the received signal is large enough, but in the actual wearing process, it is impossible to use the hand to press continuously. After physical modeling, it was found that as long as the back of the sampler does not displace relative to the body as a whole (not the chest skin), the chest skin and the sampler can be guaranteed to have relative displacement, thereby ensuring that the acoustic signal received by the sampler is large enough.

[0013] Furthermore, the closed sound cavity is composed of chest skin, flexible material and FPCB from bottom to top, and the silicon microphone is arranged on the FPCB. Both the flexible material and the FPCB are provided with through holes, which are aligned with the sound receiving holes of the MEMS analog acoustic sensor of the silicon microphone. The closed sound cavity receives vibrations transmitted by the chest skin. Since the silicon microphone is supported, the silicon microphone as a whole does not move. However, due to the beating of the heart, the surface of the chest skin moves, resulting in relative movement between the silicon microphone and the surface of the chest skin. Due to the use of a closed sound cavity, a larger proportion of the energy of the chest skin vibration is transmitted to the silicon microphone, thereby making the heart sound signal-to-noise ratio higher. Since the sampler is made of flexible material as a whole, it can be fixed on the curved skin, and after a certain supporting force is given, the sound cavity is relatively stable.

[0014] Furthermore, the open sound cavity has the same composition structure as the closed sound cavity, except that the flexible material of the open sound cavity has a channel connected to the air along the plane of the skin; the open sound cavity can receive heart sounds to a lesser extent, and such a design can achieve the goal of filtering out heart sounds as little as possible during signal differentiation.

[0015] Furthermore, the diameter of the sound receiving hole of the MEMS analog acoustic sensor is smaller than the diameter of the through hole on the FPCB, and the diameter of the through hole on the FPCB is smaller than the diameter of the through hole on the flexible material; this design can significantly reduce the resonance phenomenon caused by mismatched apertures and prevent distortion of the sound signal.

[0016] The application adopts a closed sound collecting cavity structure, so that the sound propagation path is effectively controlled; the design of the closed sound cavity helps to concentrate and strengthen the conduction of heart sound signals, thereby improving the strength and quality of the signals. Compared with the traditional open design, the closed cavity can greatly reduce the interference of environmental noise, so that the received signals mainly come from the vibration of the chest skin, and the influence of external noise is reduced, and the signal-to-noise ratio of the heart sound signal is effectively improved.

[0017] In the application, the silicon microphone is sealed in a flexible material, avoiding the problem of sound leakage caused by the gap of the silicon microphone after welding. This design effectively improves the stability of the sound collecting cavity and the signal strength received by the sensor, thereby improving the clarity and accuracy of the heart sound signal.

[0018] Since the application adopts flexible material packaging, the device can closely fit the curved surface of the human body, reducing the noise interference caused by human body movement. At the same time, the closed sound collecting cavity structure ensures the stability of the audio signal in the cavity during movement. This design takes into account various activities that users may perform during use (such as exercise, walking, etc.), so that the device can maintain good heart sound collection quality even in a moving state.

[0019] In the application, the sampler adopts an FPCB circuit board to achieve comfort and keep the sound cavity closed, and the subsequent signal processing part adopts a hard PCB circuit board to achieve high integration and stable signal processing. The two circuit boards are connected through an interface, so that the sampler is easy to replace, and the FPCB part with lower life can be replaced in time, reducing the use cost of the flexible electronic heart sound stethoscope.

[0020] Therefore, the application has the following beneficial technical effects:

[0021] 1. The application realizes noise filtering through active noise reduction technology.

[0022] 2. The application divides the PCB and FPCB boards by function, so that the FPCB part with shorter service life can be easily replaced.

[0023] 3. The application designs a flexible stethoscope probe to form a stable space for the sound collecting cavity, which is less affected by human body movement.

[0024] 4. The closed sound collecting cavity of the application changes the sound propagation path, effectively improving the signal-to-noise ratio.

[0025] 5. The application designs a reasonable acoustic structure to make the signal received by the acoustic sensor larger. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1The figure is a schematic diagram of the circuit structure of the flexible wearable electronic heart sound stethoscope of the present invention.

[0027] Figure 2 This is a schematic diagram of the silicon microphone used to collect heart sounds in the present invention.

[0028] Figure 3 This is a schematic diagram of the silicon microphone used to collect noise in the present invention.

[0029] Figure 4 This is a physical hardware schematic diagram of the flexible wearable electronic heart sound stethoscope of the present invention.

[0030] Figure 5 Schematic diagram of the stethoscope output signal (including noise) without support, the noise signal, and the signal waveform after wavelet denoising.

[0031] Figure 6 Schematic diagram of the stethoscope output signal (including noise), noise signal, and signal waveform after wavelet denoising when supported.

[0032] Figure 7 Schematic diagram of the stethoscope output signal (including noise), noise signal, and signal waveform after wavelet denoising without active noise reduction.

[0033] Figure 8 Schematic diagram of the stethoscope output signal (including noise), noise signal, and signal waveform after wavelet denoising under active noise reduction. DETAILED DESCRIPTION

[0034] In order to describe the present invention more specifically, the technical solution of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] like Figure 1 As shown, the flexible wearable electronic heart sound stethoscope of the present invention includes a sampler, a rigid PCB circuit board, and an interface for connecting the sampler and the rigid PCB circuit board. The sampler includes two MEMS analog acoustic sensors mounted on the FPCB, and the sampler is encapsulated by a flexible material; the rigid PCB circuit board includes a preamplifier, an anti-aliasing filter, and an analog-to-digital conversion module.

[0036] The key design is in the sampler part, which uses two silicon microphones to collect heart sounds and murmurs respectively. The silicon microphones contain MEMS analog acoustic sensors mounted on the FPCB. Figure 2 As shown, one of the MEMS analog acoustic sensors of the silicon microphone is in contact with the chest skin through a closed sound cavity to collect heart sounds, thereby receiving heart sounds to a greater extent; the closed sound cavity is surrounded by the flexible material, chest skin and FPCB.

[0037] like Figure 3As shown, another MEMS analog acoustic sensor of the silicon microphone is in contact with the chest skin through an open sound cavity for collecting the noise; the open sound cavity has the same structure as the closed sound cavity, except that the flexible material of the open sound cavity is provided with a channel in communication with air along the skin plane direction; the open sound cavity is used so that the heart sound is received to a smaller extent, and through such a design, the heart sound can be filtered out as little as possible in the signal difference.

[0038] As shown in Figure 2 The sound hole of the silicon microphone receives the vibration conducted by the chest skin from the closed sound cavity composed of the flexible material, the chest skin and the FPCB, and since the silicon microphone is supported, the whole silicon microphone does not displace, but due to the beating of the heart, the chest skin surface displaces, resulting in relative movement between the silicon microphone and the chest skin surface. Since the closed sound cavity is used, a large proportion of the energy of the chest skin vibration is conducted to the silicon microphone, so that the signal-to-noise ratio of the heart sound is high; since the whole sampler is made of flexible material, it can be fixed on the curved skin, and after a certain supporting force is given, the sound cavity is relatively stable.

[0039] In this embodiment, both silicon microphones of the sampler attached to the chest skin are placed facing the skin, rather than one facing the skin and one facing the outside, to prevent the noise from reflecting on the skin and causing the two silicon microphones to receive different noises, so that the noise can be filtered out as much as possible.

[0040] The sampler uses an FPCB circuit to achieve comfort and keep the sound cavity closed, and the subsequent signal processing part uses a hard PCB board to achieve high integration and stable signal processing. The two circuit boards are connected through an interface, so that the sampler is easy to replace, and the FPCB part with lower life can be replaced in time, reducing the use cost of the flexible electronic stethoscope.

[0041] As shown in Figure 2 The top of the silicon microphone is provided with a support, and the support has a sufficient rigidity to prevent the sampler from displacing relative to the whole human body, and to ensure that the MEMS analog acoustic sensor and the chest skin have relative movement. When the flexible electronic stethoscope is worn on the body, since there is no hand to provide support, it is impossible to ensure that the silicon microphone and the skin have relative movement, so the signal received by the silicon microphone is very weak. In the test, we need to use a hand to provide a sufficient support to ensure that the received signal is large enough; but in the actual wearing process, it is impossible to use the hand to press all the time, and after physical modeling, we find that as long as the sampler has no displacement relative to the whole human body (not the chest skin) at the back, the chest skin and the sampler have relative displacement, so that the acoustic signal received by the sampler is large enough. As shown in Figure 3 The silicon microphone shown in

[0042] The preamplifier in the embodiment uses an active operational amplifier and a resistor to form a single-supply in-phase proportional amplifier, which amplifies the analog signal by 10 times. The anti-aliasing filter adopts a second-order RC low-pass filter, and the cutoff frequency needs to be set above 800 Hz and below one-half of the sampling frequency, because the frequency range of the heart sound signal is 50-800 Hz, and the cutoff frequency needs to be higher than 800 Hz to prevent filtering out part of the heart sound signal; the frequency of the anti-aliasing filter needs to be lower than one-half of the sampling frequency to prevent identifying high-frequency signals as low-frequency signals. After filtering, the voltage follower can be used to increase the voltage output capability and ensure that the measured voltage is not affected by the impedance of the ADC. The analog-to-digital conversion module selects the SAADC (Successive Approximation Analog-to-Digital Converter) module of the Nrf52 series, which has a limited range (generally 0-3.6V), and the input signal needs to be DC biased to 1.8V. An 8kHz sampling rate (higher than twice the maximum frequency of the signal 800Hz) is selected, and this sampling rate has lower requirements for the device.

[0043] In addition, the Bluetooth transmission module is connected at the output end of the analog-to-digital conversion module in the embodiment, which can realize the conversion of the heart sound into a digital signal uploaded to the host computer. After the host computer collects the heart sound, the heart sound signal after active noise reduction is obtained by subtracting the digital signals collected by the two channels. Further, the differential signal can be subjected to wavelet transform denoising to filter out the remaining noise in the signal.

[0044] Verification example

[0045] In the verification example, the hardware circuit of the electronic heart sound stethoscope is built and tested, as shown in Figure 4 The red dashed box is a flexible FPCB board, and the blue dashed box is a hard PCB circuit board. In the testing process, the wavelet denoising method is used to denoise the signal, and the noise has been basically filtered out. Therefore, when calculating the signal-to-noise ratio, the signal power after wavelet denoising is taken as the numerator, and the noise power filtered out by wavelet denoising is taken as the denominator to measure the signal-to-noise ratio of the sampler.

[0046] Next, we take whether to add support to the back of the sampler and whether to actively reduce noise as two variables to control the same noise in the same group of experiments.

[0047] Back support verification:

[0048] The signal waveform without support is shown in Figure 5 The calculated signal-to-noise ratio is 7.73dB; the signal waveform after adding support to the back is shown in Figure 6As shown, the calculated signal-to-noise ratio is 20.05 dB; it can be seen that the signal-to-noise ratio of the signal collected after the support is arranged at the back of the sampler is improved, and the signal strength is also improved under the same noise.

[0049] Active noise reduction effect verification:

[0050] The signal waveform without active noise reduction is as shown in Figure 7 As shown, the calculated signal-to-noise ratio is 13.72 dB; the signal waveform after active noise reduction is as shown in Figure 8 As shown, the calculated signal-to-noise ratio is 19.07 dB; it can be seen that the signal-to-noise ratio of the signal collected after active noise reduction is improved, and part of the noise is filtered out under the same noise.

[0051] The above description of the embodiments is for the purpose of facilitating the understanding and application of the present application by those of ordinary skill in the art, and those skilled in the art can easily make various modifications to the above embodiments, and apply the general principles described herein to other embodiments without inventive labor. Therefore, the present application is not limited to the above embodiments, and any improvements and modifications of the present application made by those skilled in the art based on the disclosure of the present application shall be within the scope of protection of the present application.

Claims

1. A flexible wearable electronic heart sound stethoscope, comprising a sampler, a preamplifier, an anti-aliasing filter, and an analog-to-digital conversion module connected in sequence, characterized in that: The sampler is packaged by flexible material, which uses two silicon microphones to collect heart sound and noise respectively, and the silicon microphone contains MEMS analog acoustic sensor installed on FPCB; The preamplifier, anti-aliasing filter and analog-to-digital conversion module are installed on a hard PCB; One of the two silicon microphones is in contact with the chest skin through a closed sound cavity for collecting heart sound, and the other is in contact with the chest skin through an open sound cavity for collecting noise; The MEMS analog acoustic sensor of the silicon microphone is arranged towards the skin; The top of the silicon microphone for collecting heart sound is provided with a support with sufficient rigidity, so that the silicon microphone does not displace relative to the whole human body, and relative movement between the MEMS analog acoustic sensor and the chest skin is ensured; the top of the silicon microphone for collecting noise does not need to be provided with a support; The closed sound cavity is sequentially composed of chest skin, flexible material and FPCB from bottom to top, the silicon microphone is arranged on the FPCB, and the flexible material and the FPCB are both provided with a through hole which is aligned with the sound collecting hole of the MEMS analog acoustic sensor of the silicon microphone; The open sound cavity has the same structure as the closed sound cavity, except that the flexible material of the open sound cavity is provided with a channel which is communicated with air along the skin plane direction; The diameter of the sound collecting hole of the MEMS analog acoustic sensor is smaller than the diameter of the through hole on the FPCB, and the diameter of the through hole on the FPCB is smaller than the diameter of the through hole on the flexible material.

2. The flexible wearable electronic heart sound stethoscope of claim 1, wherein: The analog-to-digital conversion module is connected with a Bluetooth transmission module.

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