Audio signal transmission device, transfer system, modulation device, transmission method, and transfer method

Abstract

To appropriately transfer an acoustic signal such as a heart sound signal of a patient to a remote terminal in real time with minimal distortion.SOLUTION: A transmission device 80 comprises: an input unit 21 to which an acoustic signal is input; a carrier wave generation unit 23 which generates a carrier wave signal of a predetermined frequency; a modulation unit 24 which modulates the carrier wave signal with the acoustic signal to obtain a modulated signal; a multiplexing unit 31 which multiplexes the carrier wave signal and the modulated signal to obtain a multiplexed signal; and a transmission unit 32 which transmits the multiplexed signal toward a receiving device 90.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an acoustic signal transmitting device, a transmission system, a modulation device, a transmission method, etc. In particular, the present invention relates to a technology used in telemedicine for transmitting biological signals such as heart sounds and respiratory sounds as acoustic signals. [Background technology]

[0002] Telemedicine has been known for some time, in which doctors or other medical professionals (hereinafter collectively referred to as "doctors") provide real-time medical services to patients in remote locations using audio or video calls over communication lines such as telephone lines or data lines. In telemedicine, audio and video are exchanged between a terminal carried by the patient and a terminal carried by the doctor, and interviews with the patient are typically conducted through dialogue, and visual examinations are performed using video images of the patient.

[0003] In addition, in order to realize auscultation in a remote medical system, a system is known in which an electronic stethoscope is given to the patient in advance, and the heart sound signals collected by the electronic stethoscope are transmitted from the patient terminal to the doctor terminal via a data line such as the Internet, and the heart sound signals are received at the doctor terminal (Patent Document 1).

[0004] In the system described in Patent Document 1, the output signal from the electronic stethoscope is amplified by an amplifier on the transmitting device side and modulated by a modulator to generate a transmission signal within the telephone line transmission band. A carrier wave output by an oscillator is also supplied to this modulator, and the output signal from the electronic stethoscope is transmitted on both the upper and lower bands of the carrier wave. Meanwhile, on the receiving device side, the transmission signal transmitted via the telephone line network is output as a sound wave from a receiver. This sound wave is converted into an electrical signal and amplified by an amplifier, and the output is demodulated by a demodulator to restore the original output signal from the electronic stethoscope, and heart sounds and other sounds are output as sound from a speaker. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 59-032443 Summary of the Invention [Problem to be solved by the invention]

[0006] In the system described in Patent Document 1, the receiving device must separately generate a carrier wave to demodulate the transmission signal from the transmitting device and supply this carrier wave to the demodulator. In this system, the transmitting device and the receiving device must separately synchronize with each other to generate the carrier wave. However, generating a carrier wave on the receiving device side in this way takes time, making it difficult for doctors to check the patient's heartbeat in real time. In addition, this system requires the receiving device to also have a circuit for generating the carrier wave, which increases the overall circuit size of the receiving device.

[0007] Furthermore, the system described in Patent Document 1 transmits a modulated signal from a transmitting device to a receiving device via a telephone line. However, since the signal path at this time is considered to be one channel, there is also the issue that distortion occurs when the modulated signal is demodulated due to, for example, the distortion characteristics of the diode in the envelope detection circuit.

[0008] Therefore, a main object of the present invention is to provide a technology that can appropriately transmit acoustic signals such as a patient's heart sound signal to a remote terminal in real time with little distortion. [Means for solving the problem]

[0009] As a result of intensive research into means for solving the problems of the above-mentioned conventional inventions, the inventor of the present invention discovered that when a modulated signal obtained by modulating an acoustic signal obtained by an electronic stethoscope or the like with a carrier wave is transmitted from a transmitting device to a receiving device, by simultaneously transmitting the carrier wave on a channel separate from the modulated signal, it becomes unnecessary to separately generate a carrier wave at the receiving device, and the acoustic signal can be transmitted to the receiving device in real time with reduced distortion. Based on this discovery, the inventor then conceived that the problems of the conventional inventions can be solved, and completed the present invention. Specifically, the present invention has the following configuration.

[0010] A first aspect of the present invention relates to an acoustic signal transmitting device 80. The transmitting device 80 according to the present invention mainly comprises an input unit 21, a carrier wave generating unit 23, a modulating unit 24, a multiplexing unit 31, and a transmitting unit 32. An acoustic signal is input to the input unit 21. Preferably, the acoustic signal is an electrical signal obtained by converting a biological sound, such as a heart sound or a respiratory sound, acquired by an electronic stethoscope 10. However, the transmitting device 80 is not limited to this and can handle a variety of acoustic signals. The carrier wave generating unit 23 generates a carrier wave signal of a predetermined frequency. The modulating unit 24 modulates the carrier wave signal with the acoustic signal to obtain a modulated signal. The multiplexing unit 31 multiplexes the carrier wave signal and the modulated signal to obtain a multiplexed signal. The transmitting unit 32 transmits this multiplexed signal to a receiving device 90. That is, the transmitting unit 32 simultaneously transmits the carrier wave signal and the modulated signal on separate channels via a communication line such as the Internet. In this way, the transmitting device 80 of the present invention is configured to be able to simultaneously transmit a carrier signal and a modulated signal on separate channels, so that acoustic signals such as heart sound signals can be transmitted to the receiving device 90 in real time with little distortion. Furthermore, because the carrier wave for demodulation is provided to the receiving device 90 from the transmitting device 80, there is no need to provide a circuit for generating the carrier wave in the receiving device 90. Therefore, by using this transmitting device 80, the circuit scale on the receiving device 90 side can be kept small.

[0011] In the transmitting device 80 according to the present invention, the frequency of the carrier signal is preferably 1 kHz to 20 kHz. Alternatively, the frequency of the carrier signal may be 1 kHz to 10 kHz. In particular, the frequency of the carrier signal is preferably 2.5 kHz or higher. By setting the carrier signal at such a frequency, low-frequency acoustic signals such as biosignals of 1 kHz or less can be transmitted within the transmission band of audio signals commonly used in web conferencing systems using the Internet.

[0012] Preferably, the transmitting device 80 according to the present invention further includes a frequency attenuation unit 22. The frequency attenuation unit 22 attenuates frequency components above 1 kHz from the acoustic signal input to the input unit 21. Note that attenuation includes cutting out predetermined frequency components and reducing the signal strength of the predetermined frequency components. If the acoustic signal is assumed to be a biological signal, frequency components above 1 kHz can be considered noise. Therefore, by attenuating frequency components above 1 kHz from this acoustic signal, an acoustic signal with reduced noise can be transmitted to the receiving device 90.

[0013] The transmitting device 80 according to the present invention may further include an electronic stethoscope 10. In this case, a biological signal acquired by the electronic stethoscope 10 is input as an acoustic signal to the input unit 21. In this way, the electronic stethoscope 10 can also be considered to be a part of the transmitting device 80.

[0014] A second aspect of the present invention relates to an acoustic signal transmission system 100. The transmission system 100 according to the present invention includes a transmitting device 80 and a receiving device 90. The transmitting device 80 relates to the first aspect described above. The receiving device 90 receives a multiplexed signal from the transmitting device 80. The receiving device 90 includes a receiving unit 51, a separating unit 52, and a demodulating unit 63. The receiving unit 51 receives the multiplexed signal transmitted from the transmitting device 80. The separating unit 52 separates the multiplexed signal into a carrier signal and a modulated signal. The demodulating unit 63 demodulates the modulated signal with the carrier signal to obtain the pre-modulated acoustic signal. In this way, the receiving device 90 obtains the carrier signal by separating the multiplexed signal transmitted from the transmitting device 80. This eliminates the need to provide the receiving device 90 with a circuit for generating a carrier signal, thereby enabling the circuit configuration of the receiving device 90 to be made more compact.

[0015] A third aspect of the present invention relates to a modulating device 20. The modulating device 20 can be installed in the transmitting device 80 according to the first aspect. The modulating device 20 includes an input unit 21 to which an acoustic signal is input, a carrier wave generating unit 23 that generates a carrier wave signal of a predetermined frequency, a modulating unit 24 that modulates the carrier wave signal with the acoustic signal to obtain a modulated signal, and an output unit 25 that outputs the carrier wave signal and the modulated signal on different channels. In this way, the modulating device 20 can be implemented as a standalone device.

[0016] A fourth aspect of the present invention relates to a method for transmitting an acoustic signal. In the transmission method according to the present invention, first, an acoustic signal is acquired. Also, a carrier signal of a predetermined frequency is generated. Next, the carrier signal is modulated with the acoustic signal to obtain a modulated signal. Next, the carrier signal and the modulated signal are multiplexed to obtain a multiplexed signal. Next, a transmitting device 80 transmits the multiplexed signal to a receiving device 90.

[0017] A fifth aspect of the present invention relates to a method for transmitting an acoustic signal. In the transmission method according to the present invention, first, an acoustic signal is acquired. Also, a carrier signal of a predetermined frequency is generated. Next, the carrier signal is modulated with the acoustic signal to obtain a modulated signal. Next, the carrier signal and the modulated signal are multiplexed to obtain a multiplexed signal. Next, a transmitting device 80 transmits the multiplexed signal to a receiving device 90. Next, the receiving device 90 receives the multiplexed signal from the transmitting device 80. Next, the multiplexed signal is separated into a carrier signal and a modulated signal. Next, the modulated signal is demodulated with the carrier wave to obtain the acoustic signal before modulation. [Effects of the Invention]

[0018] According to the present invention, acoustic signals such as heart sound signals of a patient can be appropriately transmitted to a remote terminal in real time with little distortion. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a block diagram showing the main functions of one embodiment of the present invention. [Figure 2] FIG. 2 is a circuit diagram showing a specific example of the configuration of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below, and includes appropriate modifications of the embodiments described below within the scope obvious to those skilled in the art.

[0021] FIG. 1 shows the main functions of an acoustic signal transmission system 100 according to one embodiment of the present invention. The transmission system 100 according to this embodiment is intended for use in telemedicine. Specifically, a patient carries an electronic stethoscope 10, and biosignals such as heart sounds and respiratory sounds acquired by the electronic stethoscope 10 are output from a sound output device 70 of a doctor located in a remote location. As shown in FIG. 1, the transmission system 100 includes a transmitting device 80 located on the patient's side, a receiving device 90 located on the doctor's side, and a web server 40 that transmits and receives acoustic signals between these devices 80 and 90 over the Internet.

[0022] The transmitting device 80 modulates the biosignal (acoustic signal) acquired by the electronic stethoscope 10 and transmits it to the web server 40 via the Internet. As shown in FIG. 1 , the transmitting device 80 includes the electronic stethoscope 10, a modulating device 20, and a transmitting PC 30.

[0023] The electronic stethoscope 10 collects the patient's biological sounds, converts them into electrical signals, and outputs them. Any known electronic stethoscope may be used. For example, the electronic stethoscope 10 includes a diaphragm that directly contacts the patient's skin, a sensor that detects the vibrations (sounds) of the diaphragm, and an amplifier that amplifies the signals detected by the sensor. It is particularly preferable that the diaphragm be made of a material with a frequency characteristic that can transmit inaudible low-frequency bands below 20 Hz. An example of a diaphragm material suitable for medical applications is silicone rubber. The silicone rubber should have a hardness of 30 to 80 or 30 to 40 (measured using a Type A durometer conforming to JIS K 6253). A preferred sensor is a piezoelectric sensor. The piezoelectric sensor directly detects the vibrations of the diaphragm and converts the force (vibration) applied to the diaphragm into a voltage signal through the piezoelectric effect. A piezoelectric sensor is basically composed of a piezoelectric element and multiple electrodes sandwiching the element. The amplifier is a circuit for amplifying the signal acquired by the sensor. The biosignal thus acquired by the electronic stethoscope 10 is output to the modulation device 20.

[0024] The modulator 20 modulates the biosignal acquired by the electronic stethoscope 10 into a frequency band that can be transmitted via the Internet. Because typical data lines are primarily designed for transmitting human voice (i.e., conversation), a transmittable frequency band of approximately 0.5 to 5 kHz is sufficient. Frequency components below and above this band are often removed by audio signal processing to make human voice easier to hear. While this frequency band is sufficient for phone calls, telemedicine (especially auscultation) requires accurate transmission of various patient biosounds, including not only voice but also heart and respiratory sounds, to physicians. However, these biosounds may fall below or exceed the frequency band that can be transmitted over data lines. Therefore, transmitting biosounds over such a communication line can hinder accurate auscultation by physicians. Among the biosounds that can be detected with a typical stethoscope, heart sounds (including heart murmurs) are considered to have frequencies between 10 Hz and 500 Hz, while respiratory sounds are considered to have frequencies between 50 and 1000 Hz. Such vital sounds contain low frequency components below 100 Hz, but these frequency components below 100 Hz are removed when transmitted through a data line. Therefore, the modulator 20 modulates the low frequency band vital signals acquired by the electronic stethoscope 10 into the audio transmission band of the data line so that they can be transmitted to the receiver 90 via this data line.

[0025] As shown in FIG. 1, the modulation device 20 mainly includes an input section 21, a frequency attenuation section 22, a carrier wave generation section 23, a modulation section 24, and an output section 25.

[0026] The input unit 21 receives the acoustic signal output from the electronic stethoscope 10. For example, an audio jack or a USB terminal for transmitting acoustic signals can be used as the input unit 21. The acoustic signal input via these terminals is sent to the frequency attenuation unit 22. It is also possible to omit the frequency attenuation unit 22, in which case the acoustic signal can be transmitted directly to the modulation unit 24.

[0027] The frequency attenuation unit 22 attenuates predetermined frequency components of the acoustic signal. Specifically, the frequency attenuation unit 22 may cut frequency components exceeding 1 kHz from the acoustic signal and pass only frequency components below 1 kHz. As described above, this embodiment is intended to transmit biological sounds such as the patient's heart sounds and breathing sounds to a doctor. These biological sounds are mainly contained in the frequency band below 1 kHz, and frequencies above that are considered noise. Therefore, noise can be removed by cutting frequency components above 1 kHz from the biological signal. The frequency attenuation unit 22 may be, for example, a low-pass filter (LPF) with a cutoff frequency of 1 kHz.

[0028] The carrier wave generating unit 23 generates a carrier wave signal on which the acoustic signal is carried. The carrier wave generating unit 23 generates a carrier wave signal suitable for the audio signal transmission band of the data line. Specifically, the frequency of the carrier wave signal is preferably 1 to 20 kHz, more preferably 2.1 to 5 kHz, and particularly preferably 2.5 to 3.5 kHz. That is, considering that the audio transmission band of the Internet data line is 0.5 to 5 kHz and the frequency band of heart sounds and the like is a frequency band of about 1 Hz to 1 kHz, it is particularly preferable to set the carrier wave signal to 2.5 to 3.5 kHz as described above in order to carry all heart sound components (1 kHz) within the audio transmission band and enable appropriate demodulation on the receiving side. As the carrier wave generating unit 23, for example, an oscillation circuit such as an analog oscillator capable of generating a sine wave signal of a predetermined frequency may be used.

[0029] The modulation unit 24 generates a modulated signal by modulating the carrier signal generated by the carrier wave generation unit 23 with the acoustic signal input from the input unit 21. The modulation method used by the modulation unit 24 may be any modulation method that can convert the acoustic signal into a voice band signal using the carrier signal. Specifically, it is preferable that the modulation unit 24 performs frequency modulation (FM) to convert a low-frequency acoustic signal into a high-frequency band within the voice band. However, other modulation methods such as amplitude modulation (AM) and phase modulation (PM) can also be used.

[0030] The output unit 25 outputs the modulated signal generated by the modulation unit 24 and the carrier signal generated by the carrier wave generation unit 23 through different channels. That is, as shown in FIG. 1, the modulated signal generated by the modulation unit 24 is supplied to the output unit 25. The carrier signal generated by the carrier wave generation unit 23 is branched into two paths, one of which is supplied to the modulation unit 24 and the other to the output unit 25. Therefore, the carrier signals supplied to the modulation unit 24 and the output unit 25 are basically identical. The output unit 25 can be, for example, an audio jack or USB terminal for transmitting acoustic signals that can output stereo signals through two channels, Lch (left channel) and Rch (right channel). For example, in the example shown in FIG. 1, the modulated signal is output from Lch and the carrier signal is output from Rch. However, it is of course possible to swap the output channels of these signals. In the transmitting device 80, the output unit 25 of the modulation device 20 is connected to the transmitting PC 30. Therefore, the modulated signal and the carrier signal output from the output unit 25 are input to the transmitting PC 30 as separate channels.

[0031] The transmitting PC 30 is a device for transmitting the output signal of the modulation device 20 to the receiving device 90 via a data line such as the Internet. A typical personal computer (PC) can be used as the transmitting PC 30. Examples of PCs include desktop computers, laptop computers, tablet computers, and smartphones. A typical PC includes, for example, a processing unit, a storage unit, and a communication unit (not shown). The processing unit is composed of, for example, a processor and a memory. Examples of the processor include a well-known CPU or GPU. The processor performs predetermined arithmetic processing and image processing according to programs and data stored in the memory, and executes various control processes while writing the results of the processing to a working space in the memory. The memory is composed of, for example, a volatile memory such as RAM (Random Access Memory) and is used for the arithmetic processing by the processor. The storage unit is an element (storage) for storing data mainly used for arithmetic processing in the processing unit. The storage unit is composed of a non-volatile memory such as ROM (Read Only Memory) or flash memory, or an HDD (Hard Disk Drive). The storage unit may also store a computer program for causing the processing unit to execute predetermined processes. The communication unit is an element that enables the sending PC 30 to send and receive data to and from an external computer (e.g., a web server) via the Internet. The communication unit may be any unit that can send and receive data via wired or wireless communication. When performing wireless communication, a communication module conforming to a known wireless communication standard such as 4G, 5G, or Wi-Fi (registered trademark) may be used as the communication unit.

[0032] In this embodiment, the main functions of the transmitting PC 30 include a multiplexing unit 31 and a transmitting unit 32. The multiplexing unit 31 multiplexes the modulated signal and carrier signal output from the modulation device 20 so that these signals can be transmitted simultaneously while maintaining their respective information. A typical example of a multiplexing method is packet division multiplexing, but other well-known multiplexing methods, such as time division multiplexing, frequency division multiplexing, wavelength division multiplexing, code division multiplexing, and space division multiplexing, can also be used. Specifically, the multiplexing processing method can be in accordance with the method specified in the web conferencing application program (including the Internet browser) used by both the transmitting PC 30 and the receiving PC 50. In other words, the processing unit (processor) of the transmitting PC 30 multiplexes the modulated signal and carrier signal in accordance with the method specified in the program. For example, in the case of packet division multiplexing, the multiplexing unit 31 first converts the output signal (modulated signal and carrier signal) of the modulation device 20 into digital data by A / D conversion, and then encodes and compresses this digital data (e.g., MP3). Next, the multiplexing unit 31 packetizes the compressed digital data using a known protocol such as UDP or RTP, and separates the packetized digital data into two streams, Lch and Rch. These two streams are then transmitted using separate port numbers. The transmitting unit 32 transmits the multiplexed signal obtained by the multiplexing unit 31 to a web server 40 that provides web conference services.

[0033] The web server 40 is an online server that provides web conferencing services to the sending PC 30 and the receiving PC 50. Known online servers provided by various providers, such as Zoom (registered trademark), Teams (registered trademark), Google Meet (registered trademark), and Skype (registered trademark), may be used as the web server 40. Note that the web server 40 may also be an independently designed online server, rather than an online server provided by another private provider. While this embodiment assumes that audio signals are transmitted and received between the sending PC 30 and the receiving PC 50, it is also possible to transmit and receive image signals, such as still images and videos, in addition to audio signals, between the sending PC 30 and the receiving PC 50 via the web server 40.

[0034] The receiving device 90 receives the multiplexed signal transmitted from the transmitting device 80 via the web server 40, and restores and reproduces the biological signal from the multiplexed signal. As shown in FIG. 1, the receiving device 90 includes a receiving-side PC 50, a demodulating device 60, and a sound output device 70.

[0035] The receiving PC 50 is a device for receiving the multiplexed signal transmitted from the transmitting device 80 via a data line such as the Internet. Like the transmitting PC 30, a general-purpose personal computer (PC) can be used as the receiving PC 50. In this embodiment, the receiving PC 50 has a receiving unit 51 and a separating unit 52 as its main functions. The receiving unit 51 receives the multiplexed signal from the web server 40 and sends it to the separating unit 52. The separating unit 52 separates the modulated signal and carrier signal information from the multiplexed signal. The separating method may be selected according to the multiplexing method. For example, if the multiplexed signal is multiplexed using packet division multiplexing, two streams, Lch and Rch, are transmitted using different port numbers. Therefore, the separating unit 52 identifies the Lch and Rch based on these port numbers. The separating unit 52 then assembles and decodes the packets contained in each stream (e.g., MP3), and restores them to analog data through D / A conversion. Through this separating process, the modulated signal and carrier signal are obtained from the multiplexed signal. In the case of packet division multiplexing, the multiplexed signal has already been separated into multiple channels by the transmitting PC 30, so the receiving PC 50 can separate two channels from the multiplexed signal with simple processing. Also, in this embodiment, the multiplexed signal transmitted from the transmitting PC 30 to the receiving PC 50 includes a carrier signal, so it is not necessary to provide the receiving PC 50 with a circuit for generating a carrier signal separate from the transmitting PC 30. The modulated signal and carrier signal separated by the receiving PC 50 are output to the demodulator 60 on separate channels (Lch, Rch).

[0036] The demodulation device 60 demodulates the modulated signal using the modulated signal and carrier signal separated from the multiplexed signal. As shown in Fig. 1, the demodulation device 60 mainly includes an input section 61, a shaping section 62, a demodulation section 63, a frequency attenuation section 64, and an output section 65.

[0037] The input unit 61 receives a modulated signal and a carrier signal from the receiving PC 50 via separate channels. The input unit 61 supplies signals to different destinations for each channel. Specifically, as shown in FIG. 1, the input unit 61 supplies the carrier signal (e.g., Rch) input from the receiving PC 50 to a shaping unit 62. On the other hand, the input unit 61 supplies the modulated signal (e.g., Lch) input from the receiving PC 50 to a demodulation unit 63. As such an input unit 61, for example, an audio jack for transmitting acoustic signals, capable of stereo input of two channels, Lch and Rch, or a USB terminal can be used.

[0038] The shaping unit 62 shapes the waveform of the carrier signal. An inaccurate carrier signal may prevent proper demodulation of the modulated signal. Since this carrier signal is separated from the multiplexed signal as described above, its waveform may be distorted. Therefore, the carrier signal is shaped before being input to the demodulation unit 63. The shaping unit 62 can use, for example, a bandpass filter or a Schmitt circuit to shape the carrier signal. Alternatively, the received analog carrier signal may be digitized by an AD converter, digitally processed to generate an ideal sine wave, and then reconverted to analog by a DA converter for shaping. Furthermore, gain may be controlled by AGC (automatic gain control) to obtain a constant level of the carrier signal, thereby suppressing amplitude fluctuations. The carrier signal shaped by the shaping unit 62 in this way is supplied to the demodulation unit 63.

[0039] The demodulator 63 demodulates the modulated signal by multiplying the modulated signal received from the input unit 61 with the carrier signal received from the shaping unit 62. In this embodiment, a frequency attenuation unit 64 downstream of the demodulator 63 is also used to demodulate the modulated signal. The demodulation method used must correspond to the modulation method used on the transmitting side. For example, in the case of an FM modulated signal, the demodulator 63 differentiates the modulated signal and multiplies the differentiated signal by the carrier signal to obtain a phase difference signal between the two. Because this phase difference signal is proportional to the original modulated signal, the modulated signal can be demodulated by extracting the low-frequency components using a frequency attenuation unit 64 such as a low-pass filter. In the case of an AM modulated signal, the demodulator 63 multiplies the modulated signal by the carrier signal to generate a sum frequency component and a difference frequency component of the carrier frequency. Because this sum frequency component is a high frequency and unnecessary, it is removed using a frequency attenuation unit 64 such as a low-pass filter. The remaining difference frequency component retains the frequency spectrum of the original modulated signal, so passing it through demodulates the modulated signal. In this way, the modulated signal is demodulated to restore the acoustic signal acquired by the electronic stethoscope 10, specifically, the biological signal of 1 kHz or less, such as heart sounds and breathing sounds. The acoustic signal restored by the demodulation unit 63 and frequency attenuation unit 64 is supplied to the output unit 65.

[0040] The output unit 65 outputs the restored acoustic signal to the sound output device 70. For example, an audio jack or a USB terminal for transmitting acoustic signals can be used as the output unit 65. Note that since the restored acoustic signal is monaural, one output channel for the output unit 65 is sufficient.

[0041] The sound output device 70 reproduces sound from the acoustic signal output from the output unit 65. The sound output device 70 may be a well-known device such as a speaker, earphone, or headphone. Specifically, the sound output device 70 amplifies the acoustic signal with an amplifier and generates sound waves by the force action of a speaker coil. In the case of a digital acoustic signal, the signal may be converted into an analog signal by a DA converter (digital-to-analog converter), then amplified by an amplifier and output. To adjust the volume, a variable gain amplifier may be used, or the volume may be adjusted by signal processing in the digital domain.

[0042] In this way, in the present invention, for example, biological sounds acquired by the patient himself / herself using the electronic stethoscope 10 can be reproduced on the sound output device 70 of a remote doctor. In particular, in the present invention, the acoustic signal acquired by the electronic stethoscope 10 is modulated with a carrier signal, and this modulated signal and the carrier signal are multiplexed and then simultaneously transmitted in two channels from the transmitting device 80 on the patient side to the receiving device 90 on the doctor side, so that the biological sounds can be reproduced in real time on the sound output device 70 on the doctor side.

[0043] Next, FIG. 2 shows a specific example of the transmission system shown in FIG. 1. In particular, FIG. 2 shows an example of the specific circuit configuration of the modulator 20 and demodulator 60. As shown in FIG. 2, an acoustic signal is first input to the modulator 20 from an electronic stethoscope 10 held by a patient via an audio input terminal (input unit 21). This acoustic signal includes a heart sound signal in a frequency band of, for example, 1 Hz to 1 kHz. In the example shown in FIG. 2, a web conferencing system (web server 40) connects the transmitting PC 30 and the receiving PC 50 to enable transmission and reception of audio signals. However, since the transmission band of an audio signal is generally about 0.5 to 5 kHz, it is not possible to transmit the entire heart sound signal within the transmission band of the audio signal. For this reason, the heart sound signal is transmitted to the transmitting PC 30 and the receiving PC 50 on the upper and lower sidebands of a carrier signal within the audio band.

[0044] In the modulation device 20, an acoustic signal input from an audio input terminal is input to a low-pass filter (frequency attenuation unit 22) with a cutoff frequency of 1 kHz, which allows only frequency components below 1 kHz to pass. The acoustic signal that has passed through the low-pass filter is amplified by amplifier 26a and then input to a multiplier (modulation unit 24). Meanwhile, an oscillator (carrier wave generation unit 23) generates a 3 kHz carrier signal. This carrier signal is split into two: one is amplified by amplifier 26b and then input to a multiplier, and the other is amplified by another amplifier 26c, then passes through a low-pass filter 27a with a cutoff frequency of 5 kHz, and is output from the Rch audio output terminal (output unit 25). The carrier signal input to the multiplier is multiplied by the amplified acoustic signal in the multiplier and frequency-modulated (FM). In this modulated signal, acoustic signal components such as heart sounds appear as sidebands above and below the 3 kHz carrier component, as shown in FIG. 2. This allows acoustic signal components such as heart sounds to be transmitted using the audio transmission band of the Web conference system. The modulated signal obtained by the multiplier is amplified by amplifier 26d, passes through low-pass filter 27b with a cutoff frequency of 5 kHz, and is output from the Lch audio output terminal (output unit 25). In this way, modulation device 20 outputs the modulated signal and carrier signal to transmitting PC 30 using two channels.

[0045] The transmitting PC 30 multiplexes the modulated signal and carrier signal received from the modulation device 20 according to a predetermined protocol, and transmits these modulated signal and carrier signal to the receiving PC 50 over two channels via a web conference system on the Internet. The receiving PC 50 separates the multiplexed signal into the modulated signal and carrier signal according to a predetermined protocol. The modulated signal and carrier signal separated by the receiving PC 50 are input to the demodulation device 60.

[0046] The demodulation device 60 receives the modulated signal and carrier signal output from the transmitting PC 30 via a stereo audio input terminal (input unit 61) on different channels. The modulated signal input via the left channel is amplified by an amplifier 66a and then supplied to a multiplier (demodulation unit 63). Meanwhile, the carrier signal input via the right channel is waveform-shaped via a bandpass filter 62a and a Schmitt circuit 62b that constitute the shaping unit 62, after which it is amplified by an amplifier 66b and then supplied to the multiplier. The modulated signal input to the multiplier is multiplied by the amplified carrier signal in the multiplier. The output signal of this multiplier is then amplified by an amplifier 66c, and the low-frequency components are extracted through a low-pass filter (frequency attenuation unit 64) with a cutoff frequency of 1.3 kHz, thereby demodulating the modulated signal. By demodulating the modulated signal, an acoustic signal containing the heart sound components acquired by the electronic stethoscope 10 is restored. The acoustic signal restored in this way is output from the audio output terminal (output unit 65) to headphones (sound output device 70) worn by the doctor, thereby enabling the patient's heart sounds and the like to be transmitted in real time to a doctor in a remote location.

[0047] In the above description of the present invention, the embodiments of the present invention have been described with reference to the drawings in order to express the contents of the present invention. However, the present invention is not limited to the above embodiments, and includes modifications and improvements that are obvious to those skilled in the art based on the matters described in the present specification. [Industrial Applicability]

[0048] The present invention relates to a technology for transmitting biological sounds, and therefore can be suitably used in the medical industry. [Explanation of symbols]

[0049] 10...Electronic stethoscope 20...Modulator 21...input section 22...frequency attenuation section 23...Carrier wave generating section 24...Modulating section 25...Output unit 30...Transmitting PC 31...Multiplexing section 32...Transmission section 40...Web server 50...Receiving PC 51...receiving section 52...separating section 60... Demodulator 61... Input section 62... Shaping section 63... Demodulation section 64...Frequency attenuation section 65...Output section 70...sound output device 80...transmitting device 90... Receiving device 100... Transmission system

Claims

1. an input unit to which an acoustic signal is input; a carrier wave generating unit that generates a carrier wave signal of a predetermined frequency; a modulation unit that modulates the carrier signal with the acoustic signal to obtain a modulated signal; a multiplexing unit that multiplexes the carrier signal and the modulated signal to obtain a multiplexed signal; a transmitting unit that transmits the multiplexed signal to a receiving device. Transmitting device.

2. The frequency of the carrier signal is 1 kHz to 20 kHz. The transmitting device according to claim 1 .

3. The acoustic signal further includes a frequency attenuation unit that attenuates frequency components exceeding 1 kHz. The transmitting device according to claim 2 .

4. Further equipped with an electronic stethoscope; A biological signal acquired by the electronic stethoscope is input to the input unit as the acoustic signal.

3. The transmitting device according to claim 1 or 2.

5. 10. An acoustic signal transmission system comprising: the transmitting device according to claim 1; and a receiving device that receives the multiplexed signal from the transmitting device, The receiving device a receiving unit that receives the multiplexed signal; a separation unit that separates the multiplexed signal into the carrier signal and the modulated signal; a demodulation unit that demodulates the modulated signal with the carrier signal to obtain the acoustic signal before modulation. Acoustic signal transmission system.

6. an input unit to which an acoustic signal is input; a carrier wave generating unit that generates a carrier wave signal of a predetermined frequency; a modulation unit that modulates the carrier signal with the acoustic signal to obtain a modulated signal; an output unit that outputs the carrier signal and the modulated signal on different channels; Modulation device.

7. acquiring an acoustic signal; generating a carrier signal at a predetermined frequency; modulating the carrier signal with the acoustic signal to obtain a modulated signal; multiplexing the carrier signal and the modulated signal to obtain a multiplexed signal; a step of transmitting the multiplexed signal from the transmitting device to the receiving device. A method for transmitting acoustic signals.

8. acquiring an acoustic signal; generating a carrier signal at a predetermined frequency; modulating the carrier signal with the acoustic signal to obtain a modulated signal; multiplexing the carrier signal and the modulated signal to obtain a multiplexed signal; a step of transmitting the multiplexed signal from the transmitting device to a receiving device; a receiving device receiving the multiplexed signal from the transmitting device; separating the multiplexed signal into the carrier signal and the modulated signal; and demodulating the modulated signal with the carrier wave to obtain the unmodulated acoustic signal. A method for transmitting acoustic signals.

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