Electronic stethoscope

Abstract

To provide a medical doctor with low frequency components of biological sound difficult to hear normally, via an acoustic sense.SOLUTION: An electronic stethoscope 100 comprises: a sound collection unit 10 which acquires a sound signal; a frequency conversion unit 30 which generates a conversion signal by converting the frequency of the sound signal; and a sound emitting unit 50 which outputs the conversion signal. The frequency conversion unit 30 generates the conversion signal by modulating a carrier wave of a predetermined frequency by the sound signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electronic stethoscope. [Background technology]

[0002] In recent years, electronic stethoscopes that can pick up a patient's heart sounds, convert the sounds into digital information, and analyze or record them have become popular.

[0003] The present applicant has also proposed a medical device comprising an electronic stethoscope (vibration receiver) capable of collecting heart sounds in a frequency band including frequencies below 20 Hz, and a frequency analyzer that identifies the frequency with the highest power within this frequency band (Patent Document 1). While biological sounds, such as heart sounds, are believed to contain a variety of frequency components ranging from near 0 Hz (direct current) to over 1000 Hz, the inventor's research has revealed that biological vibrations have the most power in components around 20 Hz. Furthermore, it has been found that components around 20 Hz (particularly 0-30 Hz) are less susceptible to the operating environment of the electronic stethoscope, and that the maximum amplitude power is less likely to change even when the strength or position of the electronic stethoscope applied to the area being examined changes. Furthermore, the frequency value exhibiting maximum power is virtually unaffected by the strength or position of the electronic stethoscope applied. Therefore, by adopting an electronic stethoscope that can properly acquire frequency components below 20 Hz contained in heart sounds, such as the medical device described in Patent Document 1, and performing a process to identify the frequency with the greatest power from the frequency band acquired by the electronic stethoscope, it becomes possible to acquire highly reproducible measurement results even if the strength (pressure) or position with which the electronic stethoscope is applied to the area to be examined is not constant. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7320867 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, one of the inventor's major achievements was noticing that highly reproducible measurement results can be obtained by utilizing frequency components around 20 Hz (especially 0 to 30 Hz) of biological sounds such as heart sounds in auscultation. However, the human audible frequency range is generally considered to be 20 Hz to 20 kHz, and it is said that it is difficult for doctors to accurately hear sounds below 50 Hz. For this reason, in order to utilize sounds around 20 Hz in medical treatment, it was necessary to visually present the results of the analysis to doctors by analyzing the frequency of the sound acquired by an electronic stethoscope and displaying the analysis results on a display, as in Patent Document 1 above.

[0006] On the other hand, as mentioned above, the maximum amplitude power of sounds around 20 Hz is unlikely to change, so if doctors could directly hear these sounds in real time, it could lead to new auscultation techniques.Therefore, the main purpose of this invention is to enable doctors to use their hearing to hear the low-frequency components of biological sounds that are normally difficult to hear. [Means for solving the problem]

[0007] The inventor of the present invention has intensively studied means for solving the problems of the above-mentioned conventional inventions, and has discovered that by converting the frequency components of the acoustic signal acquired by the sound collection unit, particularly the low frequency components below 50 Hz, into the human audible frequency band and outputting them from the sound emission unit, it becomes possible to provide a doctor with sounds around 20 Hz that are useful for auscultation through their hearing. Based on this discovery, the inventor has come to the realization that the problems of the conventional inventions can be solved, and has completed the present invention. Specifically, the present invention has the following configuration.

[0008] The present invention relates to an electronic stethoscope 100. The electronic stethoscope 100 according to the present invention includes a sound collection unit 10, a frequency conversion unit 30, and a sound emission unit 50. The sound collection unit 10 acquires an acoustic signal. The acoustic signal is preferably an electrical signal obtained by converting biological sounds such as human heart sounds and breathing sounds, but the electronic stethoscope 100 is not limited to this and can handle a variety of acoustic signals. The frequency conversion unit 30 converts the frequency of the acoustic signal to generate a converted signal. The frequency conversion unit 30 may convert the frequency of the acoustic signal using analog signal processing or digital signal processing. The sound emission unit 50 outputs the converted signal as sound.

[0009] In one embodiment of the present invention, the frequency conversion unit 30 generates a converted signal by modulating a carrier wave of a predetermined frequency with an acoustic signal. In this way, by modulating the carrier wave with an acoustic signal in the low-frequency band contained in heart sounds, etc., it is possible to convert low-frequency components such as heart sounds into high-frequency components that can be recognized by the human ear. As a result, by using the electronic stethoscope 100 according to this embodiment, a doctor can recognize sounds derived from low-frequency components such as heart sounds with his or her ears, although not the low-frequency components themselves.

[0010] In one embodiment of the present invention, the frequency of the carrier wave is preferably 1 kHz to 20 kHz. In particular, the frequency of the carrier wave signal is preferably 2.5 kHz or higher. By setting the carrier wave signal at such a frequency, low-frequency acoustic signals such as biological sounds of 1 kHz or less can be easily converted into high-frequency sounds that are highly sensitive and recognizable by the human hearing.

[0011] In one embodiment of the present invention, the electronic stethoscope 100 preferably further includes a frequency attenuation unit 20, which attenuates frequency components of the acoustic signal above 1 kHz. Note that attenuation includes cutting out specific frequency components or reducing the signal strength of specific frequency components. When considering auscultation of biological sounds such as human heart sounds, frequency components above 1 kHz become noise, so attenuating these components is effective. Furthermore, when focusing on sounds below 50 Hz (or below 100 Hz), which are generally difficult for humans to hear, the frequency attenuation unit 20 may attenuate frequency components of the acoustic signal above 50 Hz.

[0012] In one embodiment of the present invention, the electronic stethoscope 100 may be configured to output the converted signal from the sound emitting unit 50 while maintaining the upper and lower sideband components contained in the converted signal. When a carrier wave is frequency-modulated with an acoustic signal, sidebands are generated above and below the carrier wave. However, by leaving these upper and lower sideband components in the converted signal, the power of the converted signal can be maintained. This allows the converted signal derived from biological sounds such as heart sounds to be transmitted to the doctor more strongly.

[0013] In one embodiment of the present invention, the frequency conversion unit 30 may include a sideband attenuation unit 34. The sideband attenuation unit 34 attenuates the upper sideband component or the lower sideband component contained in the converted signal. By attenuating one of the upper and lower sideband components from the converted signal, it is possible to transmit to the physician a converted signal that more accurately reproduces body sounds such as heart sounds.

[0014] In one embodiment of the present invention, the electronic stethoscope 100 may be configured to be switchable between a first mode in which an acoustic signal is output from the sound emitting unit 50 without being converted by the frequency conversion unit 30, and a second mode in which an acoustic signal converted by the frequency conversion unit 30 is output from the sound emitting unit 50. This configuration allows a doctor to easily compare the original heart sounds with the frequency-converted sounds.

[0015] In one embodiment of the present invention, the sound emitting unit 50 may have a first channel and a second channel. In this case, the electronic stethoscope 100 may be configured to output an acoustic signal from the first channel of the sound emitting unit 50 without conversion by the frequency conversion unit 30, and output a converted signal obtained by converting the acoustic signal by the frequency conversion unit 30 from the second channel of the sound emitting unit 50. With this configuration, a doctor can listen to the original heart sound with one ear while simultaneously listening to the frequency-converted sound with the other ear.

[0016] In another embodiment of the present invention, the frequency conversion unit 30 converts the acoustic signal to a high frequency band while maintaining its frequency ratio. In other words, the frequency conversion unit 30 performs so-called pitch conversion processing on the acoustic signal. The frequency ratio is the ratio of the magnitudes (amplitudes) of various frequency components contained in a certain acoustic signal. The frequency ratio of a sound is an important factor that determines the timbre and quality of that sound. Even sounds of the same frequency will have different timbre and quality if the frequency ratio is different. Biological sounds such as heart sounds can be considered to be sounds (in other words, chords) composed of a mixture of different frequency components. However, if the frequency ratio changes during frequency conversion, it becomes difficult for a doctor to perform auscultation. Therefore, it is preferable that the frequency conversion unit 30 converts the acoustic signal to a high frequency band while maintaining its frequency ratio, for example, by digital signal processing. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a doctor with the low frequency components of biological sounds that are normally difficult to hear through the sense of hearing. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a block diagram showing the main functions of an electronic stethoscope according to the present invention. [Figure 2] FIG. 2 is a circuit diagram showing an example of the configuration of the electronic stethoscope according to the first embodiment. [Figure 3]FIG. 3 is a circuit diagram showing an example of the configuration of an electronic stethoscope according to the second embodiment. [Figure 4] FIG. 4 is a circuit diagram showing an example of the configuration of an electronic stethoscope according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] 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.

[0020] Fig. 1 shows the main functions of an electronic stethoscope 100 according to the present invention. The electronic stethoscope 100 converts a patient's biological sounds, such as heart sounds and respiratory sounds, into electrical signals, then performs frequency conversion and outputs the converted signals again as sound. As shown in Fig. 1, the electronic stethoscope 100 includes a sound collection unit 10, a frequency attenuation unit 20, a frequency conversion unit 30, a signal amplification unit 40, a sound emission unit 50, and a memory unit 60.

[0021] The sound collection unit 10 is an element for collecting the patient's biological sounds and acquiring an acoustic signal, which is an electrical signal. A known microphone used in electronic stethoscopes can be used as the sound collection unit 10. Specifically, the sound collection unit 10 includes a diaphragm that directly contacts the patient's skin, a sensor that detects the vibration (sound) of the diaphragm, and an amplifier that amplifies the signal detected by the sensor. It is particularly preferable that the diaphragm be made of a material with a frequency characteristic capable of transmitting inaudible low-frequency bands below 50 Hz, more specifically 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 vibration 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 sandwiched between multiple electrodes. The amplifier is a circuit for amplifying the signal acquired by the sensor.

[0022] The sound collection unit 10 and the main body of the electronic stethoscope 100 are connected by an input terminal. That is, the acoustic signal acquired by the sound collection unit 10 is input to the main body of the electronic stethoscope 100 via an input terminal such as an audio jack or a USB terminal for transmitting acoustic signals. As shown in FIG. 1, the input channels of the acoustic signal from the sound collection unit 10 are preferably two or more channels, such as Rch (right channel) and Lch (left channel). The acoustic signal from the sound collection unit 10 is simply distributed to these Rch and Lch, and the same acoustic signal is input to these channels. In the example shown in FIG. 1, the Rch transmits the acoustic signal from the sound collection unit 10 to the frequency attenuation unit 20. On the other hand, the Lch transmits the acoustic signal from the sound collection unit 10 to the signal amplification unit 40 without passing through the frequency attenuation unit 20 or the frequency conversion unit 30. Note that the input channels of these signals can be interchanged.

[0023] The frequency attenuation unit 20 attenuates predetermined frequency components of the acoustic signal acquired by the sound collection unit 10. For example, the frequency attenuation unit 20 cuts frequency components exceeding 1 kHz from the acoustic signal, passing only frequency components below 1 kHz. Biological sounds, such as a patient's heart sounds and breathing sounds, are primarily contained in the frequency band below 1 kHz, and frequencies above that are considered noise. Therefore, cutting frequency components above 1 kHz from the acoustic signal can remove such noise. Alternatively, the frequency attenuation unit 20 may cut frequency components above 50 Hz or 100 Hz from the acoustic signal, passing only frequency components below 50 Hz or 100 Hz. Biological sounds, such as heart sounds, are generally considered to contain a variety of frequency components, ranging from components close to 0 Hz (DC) to components above 1000 Hz. However, research by the present inventor has revealed that components around 20 Hz have the most power in biological vibrations. Therefore, in order to focus on frequency components around 20 Hz (particularly 0 to 30 Hz), frequency components exceeding 50 Hz or 100 Hz of the acoustic signal may be cut in the frequency attenuation unit 20. For example, a low-pass filter (LPF) with the above-mentioned predetermined frequency as its cutoff frequency can be used as the frequency attenuation unit 20. The acoustic signal that has passed through the frequency attenuation unit 20 is sent to the frequency conversion unit 30.

[0024] The frequency converter 30 is a component for generating a converted signal by converting the frequency of an acoustic signal. The frequency converter 30 may be configured to convert the acoustic signal to an analog signal, or it may be configured to convert the acoustic signal to a digital signal, then convert the digital signal, and then convert it back to an analog signal. Biological sounds, such as heart sounds, primarily contain components in the frequency band below 1 kHz. However, components below 50 Hz, especially below 20 Hz, are difficult for physicians to hear. Therefore, the frequency converter 30 converts the frequency of the acoustic signal acquired by the sound collector 10 into an audible frequency band that physicians can listen to. Because the converted signal has a different frequency from the original acoustic signal, the pitch of the converted signal differs from the patient's actual biological sounds. However, by listening to the timing and tempo of the converted signal and the noise contained within it, physicians can use components in the frequency band below 20 Hz, which would otherwise be inaudible, for auscultation. The specific configuration of the frequency converter 30 will be described with reference to Figures 2 to 4.

[0025] The signal amplifier 40 amplifies the power of the converted signal obtained by the frequency converter 30. Alternatively, the original acoustic signal acquired by the sound collector 10 may be input to the signal amplifier 40 via a channel separate from the converted signal. In this case, the signal amplifier 40 also amplifies the power of the original acoustic signal from the sound collector 10. The signal amplifier 40 may be, for example, a known high-power amplifier (HPA). The HPA amplifies the input signal with a predetermined gain. Specifically, the HPA uses active elements such as transistors and electron tubes to impart a large power gain to the input signal, thereby increasing the power of the output signal. The HPA's gain, linearity, and other characteristics can be designed as appropriate depending on the purpose and application. The signal amplified by the HPA is basically sent to the sound emitter 50 via an output terminal.

[0026] As shown in FIG. 1, the signal amplifier 40 can receive the original acoustic signal from the sound collection unit 10 and the converted signal from the frequency conversion unit 30 via separate channels. In this case, the signal amplifier 40 amplifies the original acoustic signal and the converted signal. The signal amplifier 40 then outputs the amplified acoustic signal and the converted signal via separate channels. In the example shown in FIG. 1, for example, the converted signal is output via Rch, and the unconverted acoustic signal is output via Lch. The output channels of these signals can also be interchanged.

[0027] The main body of the electronic stethoscope 100 and the sound emitting unit 50 are connected by an output terminal. That is, the output signal from the signal amplifier unit 40 is input to the sound emitting unit 50 via this output terminal. The output terminal may be, for example, an audio jack for transmitting acoustic signals capable of stereo output on two channels, Rch and Lch, or a USB terminal. Specifically, the converted signal that has been frequency-converted via the frequency converter 30 is output, for example, from the Rch output terminal and is output from the right ear side of the sound emitting unit 50, which is made up of headphones. Furthermore, the unconverted acoustic signal that has not passed through the frequency converter 30 is output, for example, from the Lch output terminal and is output from the left ear side of the sound emitting unit 50, which is made up of headphones.

[0028] The sound emitting unit 50 reproduces sound from the output signal from the output terminal. The sound emitting unit 50 may be a well-known device such as a speaker, earphone, or headphone. Specifically, the sound emitting unit 50 amplifies the output signal from the main body of the electronic stethoscope 100 using an amplifier, and generates sound waves by the force action of the speaker coil. In the case of a digital acoustic signal, the signal is converted into an analog signal using a DA converter (digital-to-analog converter), and then amplified by an amplifier before being output. The volume can also be adjusted using a variable gain amplifier or by signal processing in the digital domain.

[0029] The sound emitting unit 50 may be configured to be switchable between a stereo mode, in which a converted signal input via the left channel and an unconverted acoustic signal input via the right channel are simultaneously output on the left and right channels, and a monaural mode, in which either a converted signal input via the left channel or an unconverted acoustic signal input via the right channel is selected and output. In the monaural mode, it may be possible to arbitrarily select whether to output the converted signal input via the left channel or the unconverted acoustic signal input via the right channel. Specifically, in the stereo mode, a physician can listen to the patient's original body sounds, such as heart sounds, with his / her left ear, while simultaneously listening to the converted sounds obtained by frequency-converting the body sounds with his / her right ear. In the monaural mode, a physician can select either the patient's original body sounds, such as heart sounds, or the converted sounds obtained by frequency-converting the body sounds, and listen to only one of them.

[0030] In the above explanation, the sound emitting unit 50 is provided with the function of switching between stereo mode and mono mode, and the function of selecting the output signal (converted signal and unconverted acoustic signal) in mono mode. However, these switching and selection functions can also be provided on the main body of the electronic stethoscope 100, specifically, in the signal amplifier unit 40 (HPA) or the like.

[0031] In addition to the above elements, the electronic stethoscope 100 may further include a memory unit 60. The memory unit 60 is an element for at least temporarily storing a signal to be output to the sound output unit 50. Specifically, in the example shown in FIG. 1 , a signal is output from the signal amplifier unit 40 to the sound output unit 50, but the same signal can also be output and stored in the memory unit 60. The signal stored in the memory unit 60 can also be read by the signal amplifier unit 40 and output to the sound output unit 50. As described above, when a frequency-converted converted signal and an unconverted signal are output on separate channels for a certain acoustic signal, it is preferable to store the converted signal and the unconverted acoustic signal in association with each other in the memory unit 60. When storing a signal in the memory unit 60, a process for converting an analog acoustic signal into a digital signal may be performed. Conversely, when reading a signal from the memory unit 60, a process for converting a digitally stored acoustic signal into an analog signal may be performed. The storage unit 60 may be a volatile memory such as a random access memory (RAM), a non-volatile memory such as a read only memory (ROM) or a flash memory, or a hard disk drive (HDD).

[0032] Next, a first embodiment of the electronic stethoscope 100 will be described with reference to FIG. 2. In particular, FIG. 2 shows a specific configuration of the frequency conversion unit 30. As shown in FIG. 2, in the electronic stethoscope 100 according to the first embodiment, a sound collection unit 10 (microphone) collects biological sounds such as the patient's heart sounds and breathing sounds, converts them into acoustic signals, and inputs them into the electronic stethoscope 100 main body via two channels, Rch and Lch. Heart sounds are expected to include sounds in the frequency band of 1 Hz to 1 kHz. The acoustic signal input via Rch is input to the frequency conversion unit 30 via the frequency attenuation unit 20. A low-pass filter with a cutoff frequency of 1 kHz is used as the frequency attenuation unit 20. On the other hand, the acoustic signal input via Lch is input directly to the signal amplification unit 40 (HPA) without passing through the frequency attenuation unit 20 or the frequency conversion unit 30.

[0033] In this embodiment, an analog modulation circuit that modulates a carrier signal with an acoustic signal such as a heart sound is used as the frequency conversion unit 30. Specifically, the frequency conversion unit 30 includes a modulator 31, an oscillator circuit 32, and a plurality of amplifiers 33.

[0034] The modulation unit 31 generates a converted signal by modulating the carrier signal generated by the oscillation circuit 32 with the acoustic signal acquired by the sound collection unit 10. Specifically, the modulation unit 31 performs frequency modulation (FM) to convert the low-frequency acoustic signal to a high frequency band within the voice band. A known multiplier may be used as the modulator 31. The oscillation circuit 32 generates a carrier signal on which the acoustic signal is carried. The frequency of the carrier signal is preferably 1 to 20 kHz, more preferably 2.1 to 5 kHz, and particularly preferably 2.5 to 3.5 kHz. In this embodiment, to convert an acoustic signal in the range of 0 to 1 kHz into a frequency band within the human high sensitivity range (approximately 1.5 to 4.5 kHz), the frequency of the carrier signal is selected from the range of 2.5 to 3.5 kHz, specifically set to 3 kHz. The oscillation circuit may be, for example, an analog oscillator capable of generating a sine wave signal of a predetermined frequency. When the carrier signal is modulated with the acoustic signal in this manner, sideband components appear above and below the carrier component in the converted signal. In this embodiment, the sound of the converted signal is output from the sound emitting unit 50 while maintaining the upper sideband component and the lower sideband component. Furthermore, the multiple amplifiers 33 may be disposed at appropriate locations within the frequency conversion unit 30. For example, the first amplifier 33(a) amplifies the acoustic signal before it is input to the modulator 31, the second amplifier 33(b) amplifies the carrier signal before it is input to the modulator 31, and the third amplifier (c) amplifies the converted signal generated by the modulator 31.

[0035] The converted signal obtained by the frequency conversion unit 30 configured as described above is amplified again by the signal amplification unit 40 (HPA) at a predetermined gain, output on the Rch, and output as sound from the sound emission unit 50. On the other hand, the acoustic signal input to the Lch of the sound collection unit 10 is input directly to the signal amplification unit 40 (HPA) without passing through the frequency attenuation unit 20 or the frequency conversion unit 30. This original acoustic signal is amplified by the signal amplification unit 40 (HPA) at a predetermined gain, output on the Lch, and output as sound from the sound emission unit 50. As described above, the sound emission unit 50 (headphones) can output the Rch converted signal and the Lch acoustic signal simultaneously in stereo mode, or can select either the Rch converted signal or the Lch acoustic signal and output it in monaural mode.

[0036] Next, a second embodiment of the electronic stethoscope 100 will be described with reference to FIG. 3. Note that in the following embodiment, explanation of the same components as those in the first embodiment will be omitted, and the description will focus mainly on the components that differ from those in the first embodiment. As shown in FIG. 3, the frequency conversion section 30 in the second embodiment differs from the first embodiment in that it further includes a sideband attenuation section 34, located after the modulator 31, for attenuating either the upper or lower sideband components contained in the modulated signal. This sideband attenuation section 34 is not included in the first embodiment. In other respects, the second embodiment is basically the same as the first embodiment.

[0037] As described above, the converted signal obtained by the modulator 31 includes an upper sideband component and a lower sideband component, and the sideband attenuation unit 34 is provided to remove one of these sidebands. In the example shown in FIG. 3, the sideband attenuation unit 34 cuts the lower sideband component from the converted signal. In this case, a high-pass filter with a cutoff frequency approximately equal to the frequency of the carrier signal may be used as the sideband attenuation unit 34. Although not shown, the sideband attenuation unit 34 can also be used to cut the upper sideband component from the converted signal. In this case, a low-pass filter with a cutoff frequency approximately equal to the frequency of the carrier signal may be used as the sideband attenuation unit 34. As described above, in this embodiment, either the upper sideband component or the lower sideband component is cut from the converted signal, and the resulting sound is output from the sound emitting unit 50.

[0038] Next, a third embodiment of the electronic stethoscope 100 will be described with reference to FIG. 4. In the second embodiment, instead of an analog modulation circuit, a digital signal processing device (DSP) 35 is used as the frequency conversion unit 30. This digital signal processing device can convert an acoustic signal, such as a heart sound, into a digital signal, adjust its frequency, and then convert it back into an analog signal. The DSP 35 mainly includes a calculation processor, a program memory, a data memory, and the like. The calculation processor can access programs in the program memory and data in the data memory to perform various acoustic processing operations on the digitized acoustic signal. A known device having such functions can be used as the DSP 35.

[0039] In this embodiment, it is important to convert the frequency of a biological sound, such as a heart sound, into an audible range (especially a high-sensitivity range) that is easily audible to physicians, while minimizing the change in the information contained in the biological sound itself. Therefore, it is preferable for the DSP 35 to convert the biological sound into a high-frequency band while maintaining the frequency ratio of the biological sound. For example, assume that an acoustic signal obtained from the biological sound has a frequency spectrum in which the 10 Hz component has an amplitude of 1, the 20 Hz component has an amplitude of 2, and the 50 Hz component has an amplitude of 0.5. In this case, the frequency ratio of this acoustic signal is 10 Hz:20 Hz:50 Hz:=1:2:0.5. Such a frequency ratio of a sound is an important factor in determining the timbre and sound quality of the sound. Therefore, the DSP 35 obtains a converted signal that shares the timbre and sound quality of the original acoustic signal by shifting only the frequency band while maintaining the frequency ratio of the acoustic signal. One method for obtaining such a converted signal is to change the pitch (fundamental frequency) of the acoustic signal. Pitch conversion methods include pitch shifting, which changes the pitch by shifting the entire frequency spectrum of the audio signal, and time stretching, which changes the pitch by expanding or contracting the time axis of the audio signal. Of these, pitch shifting is preferred because it is less likely to disrupt the frequency ratio and is easier to maintain the sound quality of the audio signal than time stretching.

[0040] In the third embodiment, as in the first and second embodiments described above, the converted signal from the frequency conversion unit 30 (DSP 35) is amplified by the signal amplification unit 40 (HPA) and then output to the sound emission unit 50 via the Rch. In this way, the converted signal is output as sound from the sound emission unit 50. The sound of the converted signal sounds high-pitched because its frequency has been increased from the original body sound, but because the frequency ratio is maintained from the original body sound, there is a certain degree of commonality with the original body sound in terms of timbre and sound quality. Therefore, a doctor may be able to discover that an abnormal sound or noise is contained in the patient's body sound just from the sound of the converted signal.

[0041] 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]

[0042] The present invention relates to an electronic stethoscope, and therefore can be suitably used in the medical industry. [Explanation of symbols]

[0043] 10...Sound collection section 20...Frequency attenuation section 30...Frequency conversion unit 31...Modulator 32...Oscillator circuit 33...Amplifier 34... Sideband attenuation unit 35... Digital signal processing unit (DSP) 40: Signal amplifier section 50: Sound output section 60...Memory unit 100...Electronic stethoscope

Claims

1. a sound collection unit for acquiring an acoustic signal; a frequency conversion unit that converts the frequency of the acoustic signal to generate a converted signal; a sound emitting unit that outputs the conversion signal, The frequency conversion unit generates the converted signal by modulating a carrier wave of a predetermined frequency with the acoustic signal. Electronic stethoscope.

2. The frequency of the carrier wave is 1 kHz to 20 kHz.

10. The electronic stethoscope of claim 1.

3. The acoustic signal further includes a frequency attenuation unit that attenuates frequency components exceeding 1 kHz.

10. The electronic stethoscope of claim 1.

4. The converted signal is output from the sound output unit while maintaining the upper sideband component and the lower sideband component contained in the converted signal.

10. The electronic stethoscope of claim 1.

5. The frequency conversion unit has a sideband attenuation unit that attenuates an upper sideband component or a lower sideband component included in the converted signal.

10. The electronic stethoscope of claim 1.

6. The device is configured to be able to switch between a first mode in which the acoustic signal is output from the sound output unit without being converted by the frequency conversion unit, and a second mode in which the acoustic signal is converted by the frequency conversion unit and the converted signal is output from the sound output unit.

10. The electronic stethoscope of claim 1.

7. the sound emitting unit has a first channel and a second channel, The acoustic signal is output from the first channel of the sound emitting unit without being converted by the frequency conversion unit, and the converted signal obtained by converting the acoustic signal by the frequency conversion unit is output from the second channel of the sound emitting unit.

10. The electronic stethoscope of claim 1.

8. a sound collection unit for acquiring an acoustic signal; a frequency conversion unit that converts the frequency of the acoustic signal to generate a converted signal; a sound emitting unit that outputs the conversion signal, The frequency conversion unit converts the acoustic signal into a high frequency band while maintaining the frequency ratio. Electronic stethoscope.

Images