Heart sound detection device and heart sound detection method

Abstract

To provide a heart sound detector and a heart sound detection method capable of presenting to a medical care worker such as a doctor, states of A2 and P2 constituting an II sound, in a manner of capable of easily grasping the states.SOLUTION: A heart sound detector comprises: an acquisition part for acquiring a heart sound diagram of a subject; an II sound position detecting part for detecting a position of an II sound included in the heart sound diagram; a wavelet transformation part for performing wavelet transformation to the heart sound diagram with a prescribed window width including, the II sound position detected by the II sound detecting part; and a display part for displaying a time frequency analysis image being obtained by the wavelet transformation.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a heart sound detection device and a heart sound detection method for detecting the second heart sound from heart sounds.

Background Art

[0002] Heart sounds include the first heart sound based on the closure of the mitral valve and the tricuspid valve, and the second heart sound based on the closure of the aortic valve. More specifically, the second heart sound is composed of an aortic component (which may be simply abbreviated as A2 hereinafter since it is generally called A2) and a pulmonary artery component (which may be simply abbreviated as P2 hereinafter since it is generally called P2). It is known that the characteristics (e.g., the state of A2 and P2) appearing in the second heart sound change depending on the severity of aortic valve stenosis.

[0003] Patent Document 1 and the like disclose a device for determining the presence and severity of heart disease based on the splitting state of the second heart sound in heart sounds.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, normally, the second heart sound appears in the order of A2 and P2, and during exhalation, they appear almost simultaneously, so it sounds like one sound to the human ear. However, as the severity of aortic valve stenosis increases, the intensity of A2 weakens, and in addition, since the ventricular ejection time is prolonged, A2 may appear later than P2. Furthermore, as the disease progresses, A2 disappears due to valve immobilization.

[0006] Also, the second heart sound splits physiologically. For example, the degree of splitting of the second heart sound also changes depending on exhalation and inhalation during breathing.

[0007] Conventional methods for detecting the second heart sound (S1) primarily involve defining a detection period based on the electrocardiogram signal and then performing a threshold judgment on the phonocardiogram within that period.

[0008] However, with this method, the accuracy of detecting the second heart sound is significantly reduced if noise is present in the phonocardiogram or if the T wave of the electrocardiogram is not measured correctly.

[0009] The present invention has been made in consideration of the above points, and provides a heart sound detection device and heart sound detection method that can easily present the state of A2 and P2, which constitute the second heart sound, to medical professionals such as doctors. [Means for solving the problem]

[0010] One aspect of the heart sound detection device of the present invention is An acquisition unit that acquires the patient's phonocardiogram, A second heart sound position detection unit for detecting the position of the second heart sound included in the aforementioned phonocardiogram, A wavelet transform unit performs a wavelet transform on a phonocardiogram of a predetermined window width that includes the position of the second heart sound detected by the second heart sound position detection unit. A display unit that displays a time-frequency analysis image obtained by wavelet transform, It is equipped with.

[0011] One embodiment of the heart sound detection method of the present invention is: Steps to obtain the patient's phonocardiogram, The steps include detecting the location of the second heart sound included in the phonocardiogram, The steps include: applying a wavelet transform to a phonocardiogram of a predetermined window width that includes the detected second heart sound position; The steps include displaying the time-frequency analysis image obtained by wavelet transform, Includes. [Effects of the Invention]

[0012] According to the present invention, it becomes possible to easily present the states of A2 and P2 that constitute the second heart sound to medical workers such as doctors.

Brief Description of the Drawings

[0013] [Figure 1] FIG. 1A is a diagram showing the original phonocardiogram before analysis, FIG. 2B is a diagram showing the time-frequency analysis image, FIG. 1C is a diagram showing the frequency power spectrum image, FIG. 1D is a diagram showing the peak frequency power waveform, FIG. 1E is a diagram showing the first-order differential waveform, FIG. 1F is a diagram showing the second-order differential waveform, and FIG. 1G is a diagram showing the third-order differential waveform. [Figure 2] It is a diagram showing an example of a subject who does not have aortic stenosis. FIG. 2A is a diagram showing the phonocardiogram, FIG. 2B is a diagram showing the time-frequency analysis image, and FIG. 2C is a diagram showing the frequency power spectrum image. [Figure 3] It is a diagram showing an example of a patient with aortic stenosis determined to be of the right leg block type. FIG. 3A is a diagram showing the phonocardiogram, FIG. 3B is a diagram showing the time-frequency analysis image, and FIG. 3C is a diagram showing the frequency power spectrum image. [Figure 4] It is a diagram showing an example of a patient with aortic stenosis who is a target of dobutamine stress. FIG. 4A is a diagram showing the phonocardiogram, FIG. 4B is a diagram showing the time-frequency analysis image, and FIG. 4C is a diagram showing the frequency power spectrum image. [Figure 5] Diagram showing the overall configuration of the blood pressure pulse wave inspection device according to the embodiment [Figure 6] Block diagram showing the main configuration of the heart sound detection device in the embodiment [Figure 7] Flowchart for explaining the operation until the start point and end point of the second heart sound are detected according to the embodiment

Modes for Carrying Out the Invention

[0014] <1>Principle Before explaining the embodiment, the principle of the present invention will be explained.

[0015] FIG. 1A is a diagram showing the original phonocardiogram before analysis.

[0016] Figure 1B is a diagram showing a time-frequency analysis image obtained by performing wavelet transform on the phonocardiogram of Figure 1A. In the present invention, first, the position of the second heart sound in the phonocardiogram is detected. Next, wavelet transform is performed on the phonocardiogram with a predetermined window width centered on the detected position. Here, various conventionally proposed methods such as a method of detecting based on the end position of the T wave in an electrocardiogram can be applied to the detection of the position of the second heart sound.

[0017] In the present invention, the time-frequency analysis image obtained by wavelet transform as shown in Figure 1B is displayed on the display unit. As a result, medical staff such as doctors can visually grasp the splitting state of A2 and P2 in the frequency direction and time direction. Since at least the splitting state of A2 and P2 in the frequency direction and time direction can be visually seen, medical staff such as doctors can use this as an index for diagnosing aortic valve stenosis and the like.

[0018] Here, the window for performing wavelet transform may be set, for example, such that the start point of the window is -80 ms from the start point of the second heart sound and the end point of the window is +80 ms from the end point of the second heart sound.

[0019] However, the position of the window is not limited to this. The position of the window may be set to include at least the second heart sound.

[0020] The position of the window is preferably set not to have the width from the start point to the end point of the second heart sound in the time direction, but to have a certain margin forward from the start point of the second heart sound and backward from the end point of the second heart sound, as in the above-described example. By doing so, for example, even when there is an error in the position detection accuracy of the second heart sound, an effect such as reducing this influence can be obtained.

[0021] The position of the window is more preferably set so as not to include adjacent first heart sounds or third heart sounds. By doing so, the influence of the first heart sound and the third heart sound on the time-frequency analysis image is eliminated, and the splitting state of the second heart sound can be presented to medical staff more clearly.

[0022] The window position should, more preferably, be set to a location that minimizes the inclusion of systolic and diastolic noise. This prevents the time-frequency analysis image from being affected by systolic and diastolic noise, making it easier for medical professionals to understand the splitting state of the second heart sound.

[0023] Figure 1C shows a frequency power spectrum image obtained by applying a Global Wavelet Spectrum (GWS) operation to the time-frequency analysis results of Figure 1B. In this invention, a frequency power spectrum image like the one shown in Figure 1C is displayed on the display unit. This allows medical professionals to visually grasp the bimodal nature of A2 and P2 and the peak frequencies, which can be used as an indicator for diagnosing conditions such as aortic valve stenosis.

[0024] Figure 1D shows the power analysis of the original phonocardiogram, focusing on the peak frequencies detected by GWS calculation (i.e., the power waveform in the time direction of the peak frequencies).

[0025] Figures 1E, 1F, and 1G show the waveform obtained by the first, second, and third derivatives of the peak frequency power waveform in Figure 1D, respectively.

[0026] In this invention, the start and end points of the second heart sound (S2) included in the phonocardiogram are detected using the third-order differential waveform shown in Figure 1G. This allows for precise detection of the timing of the S2 heart sound's occurrence. This occurrence timing can be clearly indicated, for example, in the time-frequency analysis image in Figure 1B, as shown by the dotted line in the figure.

[0027] Incidentally, the waveforms in Figures 1D, 1E, 1F, and 1G illustrate the calculation process and are not meant to be displayed on the display unit. However, they could, of course, be displayed on the display unit.

[0028] Figure 2 shows the phonocardiogram (Figure 2A), time-frequency analysis image (Figure 2B), and frequency power spectrum image (Figure 2C) of a subject without aortic valve stenosis.

[0029] Figure 3 shows the phonocardiogram (Figure 3A), time-frequency analysis image (Figure 3B), and frequency power spectrum image (Figure 3C) of a patient with aortic stenosis diagnosed as right bundle branch block type by electrocardiogram.

[0030] Figure 4 shows the phonocardiogram (Figure 4A), time-frequency analysis image (Figure 4B), and frequency power spectrum image (Figure 4C) of a patient with aortic stenosis who was a candidate for dobutamine loading (left ventricular ejection fraction (LVEF) < 50 and mean pressure gradient (mPG) < 40).

[0031] Medical professionals can diagnose the progression of aortic valve stenosis by using time-frequency analysis images (Figures 2B, 3B, and 4B) and frequency power spectrum images (Figures 2C, 3C, and 4C) as indicators.

[0032] According to the present invention, it is possible to visually represent the extent to which A2 and P2 are split in the time and frequency directions. Furthermore, by using differential waveforms, the start and end points of the second tone can be precisely determined.

[0033] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0034] <2> Overall configuration of a blood pressure and pulse wave analysis device Figure 5 shows the overall configuration of the blood pressure pulse wave examination device 1 to which the heart sound detection device and heart sound detection method of the present invention are applied.

[0035] In Figure 5, the main body 1a of the blood pressure pulse wave testing device 1 is equipped with a calculation processing unit 10, an input unit 70, a display unit 80, a printing unit 91, a storage unit 92, an audio output unit 93, a blood pressure pulse wave measurement unit 30, a heart sound measurement unit 40, an electrocardiogram measurement unit 50, and a pulse wave measurement unit 60.

[0036] The blood pressure pulse wave measurement unit 30 includes an upper arm measurement control unit 31 and a lower limb measurement control unit 32. The upper arm measurement control unit 31 is connected to the right upper arm cuff 21R and the left upper arm cuff 21L via hoses 21h, and the lower limb measurement control unit 32 is connected to the right ankle cuff 22R and the left ankle cuff 22L via hoses 22h.

[0037] A heart sound microphone 23 is connected to the heart sound measurement unit 40. Limb electrocardiogram electrodes 24a and chest electrocardiogram electrodes 24b are connected to the electrocardiogram measurement unit 50. Amorphous pulse wave sensors 25a and 25b are connected to the pulse wave measurement unit 60.

[0038] The arithmetic processing unit 10 is a computer that includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and various interfaces. The arithmetic processing unit 10 performs calculations and other processing to realize each function of the heart sound detection unit 100 shown in Figure 6, which will be described below, by executing a control program stored in ROM using the CPU.

[0039] Furthermore, the arithmetic processing unit 10 controls the upper arm measurement control unit 31, the lower limb measurement control unit 32, the heart sound measurement unit 40, the electrocardiogram measurement unit 50, and the pulse wave measurement unit 60 (hereinafter referred to as "each biological information measurement unit") which measure various types of biological information.

[0040] Furthermore, the arithmetic processing unit 10 receives biological information supplied from each biological information measurement unit. When it is necessary to display the received biological information on the screen, it edits or converts it into display data and outputs it to the display unit 80. When it is necessary to print the information on report paper, it edits or converts it into print data and outputs it to the print unit 91. The arithmetic processing unit 10 also stores the received biological information in the storage unit 92 as appropriate, and reads the stored biological information.

[0041] Furthermore, the arithmetic processing unit 10 performs waveform analysis of the biological information received from each biological information measurement unit. In the waveform analysis, it detects characteristic parts (section points) in the waveform. Examples of characteristic parts include the start of the second heart sound, the rising edge of the pulse wave in the upper arm, the rising edge of the pulse wave in the ankle, and the notch of the pulse wave in the upper arm.

[0042] The calculation processing unit 10 calculates the degree of arteriosclerosis based on the analysis results and the numerical values ​​(e.g., blood pressure) indicated by the received biological information.

[0043] Furthermore, the arithmetic processing unit 10 receives input and instructions from the user via the input unit 70, and, according to the received content, sets the functions related to each biometric information measurement unit, display unit 80, printing unit 91, storage unit 92, and audio output unit 93, and controls the start and stop of their respective operations.

[0044] The display unit 80 is a display device having a display screen such as an LCD (Liquid Crystal Display), and displays biological information, analysis results, and arteriosclerosis degree, etc., which are input as display data from the arithmetic processing unit 10, on the screen.

[0045] The printing unit 91 mainly consists of a paper feeding mechanism and a print head, and prints biological information, analysis results, and arteriosclerosis degree, which are input as print data from the calculation processing unit 10, onto the paper.

[0046] The memory unit 92 is composed of a hard disk drive, a writable optical disk drive, non-volatile memory, etc., and is capable of storing information from the arithmetic processing unit 10. In addition, the memory unit 92 records biological information measured by each biological information measurement unit, namely electrocardiograms, pulse waves, and heart sounds.

[0047] The audio output unit 93 mainly consists of a speaker and outputs guidance voice or notification sound according to guidance data or notification sound output instruction signals input from the arithmetic processing unit 10.

[0048] The input unit 70 consists of a keyboard, mouse, buttons, touch panel, etc., and receives input and instructions from the user and sends them to the arithmetic processing unit 10.

[0049] The pulse wave measurement unit 60 supplies the pulse wave signals of the subject detected by amorphous pulse wave sensors 25a and 25b, which are appropriately attached to the subject, to the calculation processing unit 10. This allows for the measurement and analysis of the pulse wave. One of the amorphous pulse wave sensors 25a and 25b is attached, for example, to the subject's carotid artery, and the other is attached, for example, to the subject's femoral artery or knee.

[0050] In this embodiment, the blood pressure pulse wave measurement unit 30 consists of an upper limb measurement control unit 31 and a lower limb measurement control unit 32, which are provided separately. However, the upper limb measurement control unit 31 and the lower limb measurement control unit 32 may be integrated into a single unit. Since known techniques can be used for measuring blood pressure pulse waves using the blood pressure pulse wave measurement unit 30 having an upper limb measurement control unit 31 and a lower limb measurement control unit 32, a detailed explanation is omitted here.

[0051] The electrocardiogram measurement unit 50 supplies the electrocardiogram signals detected by the limb electrocardiogram electrode units 24a and the chest electrocardiogram electrode unit 24b attached to the subject to the calculation processing unit 10. This allows for the measurement and analysis of the electrocardiogram. The limb electrocardiogram electrode unit 24a typically consists of four electrocardiogram electrodes attached to the right wrist, left wrist, right ankle, and left ankle, respectively. Regarding the electrocardiogram electrodes for both ankles, it is preferable that they are designed so that attachment to both ankles is not hindered by the right ankle cuff 22R and the left ankle cuff 22L. The chest electrocardiogram electrode unit 25b typically consists of six electrocardiogram electrodes attached to six locations on the chest, respectively.

[0052] The heart sound measurement unit 40 supplies the heart sound signal detected by the heart sound microphone 23 attached to the subject to the processing unit 10. This enables the measurement and analysis of heart sounds.

[0053] <3> II tone detection processing according to this embodiment The arithmetic processing unit 10 of this embodiment has a function to detect the state of the second heart sound (S2) included in the phonocardiogram. In practice, the arithmetic processing unit 10 has a heart sound detection unit 100 as shown in Figure 6, and the heart sound detection unit 100 detects the state of the second heart sound.

[0054] The heart sound detection unit 100 inputs the phonocardiogram measured by the heart sound measurement unit 40 and stored in the memory unit 92 to the second sound position detection unit 101. The second sound position detection unit 101 detects the position of the second sound in the phonocardiogram. For example, the second sound position detection unit 101 detects the end of the T wave in the electrocardiogram as the start of the second sound. Note that the method of detecting the second sound by the second sound position detection unit 101 is not limited to this, and various conventionally proposed methods can be applied. The position information of the second sound obtained by the second sound position detection unit 101 is sent to the wavelet transform unit 102. Note that the second sound position information sent from the second sound position detection unit 101 to the wavelet transform unit 102 is not limited to the start position of the second sound, but may also be the center position or end position of the second sound, or even the approximate position of the second sound.

[0055] The wavelet transform unit 102 receives the phonocardiogram and second heart sound (H2) position information as input and applies a wavelet transform to the phonocardiogram within a predetermined window width centered on the H2 position to obtain a time-frequency analysis image as shown in Figure 1B. This time-frequency analysis image is displayed on the display unit 80 via the display control unit 81. Note that the window of the wavelet transform unit 102 does not necessarily have to be centered on the H2 position detected by the H2 position detection unit 101. In short, it is sufficient that one H2 is always included within the window.

[0056] Furthermore, the heart sound detection unit 100 inputs the output of the wavelet transform unit 102 to the GWS calculation unit 103. The GWS calculation unit 103 performs a GWS (Global Wavelet Spectrum) calculation on the phonocardiogram to obtain a frequency power spectrum image as shown in Figure 1C. This frequency power spectrum image is displayed on the display unit 80 via the display control unit 81.

[0057] Furthermore, the heart sound detection unit 100 inputs the phonocardiogram to the peak frequency power waveform calculation unit 104. The peak frequency power waveform calculation unit 104 receives peak frequency information from the GWS calculation unit 103 and obtains the peak frequency power waveform (Figure 1D), which is the power waveform in the time direction of the phonocardiogram for the peak frequency.

[0058] Furthermore, the heart sound detection unit 100 includes a differential calculation unit 105 and a start / end point detection unit 106. The differential calculation unit 105 obtains a third-order derivative waveform (Figure 1G) by performing the third-order derivative of the peak frequency power waveform (Figure 1D), and outputs this to the start / end point detection unit 106.

[0059] The start and end point detection unit 106 detects the start and end points of the second tone by detecting the intersection of the third-order differential waveform with the baseline. This start and end point information is displayed on the display unit 80 via the display control unit 81. For example, based on the start and end point information, the start and end points of the second tone are clearly indicated in the time-frequency analysis image of Figure 1B, as shown by the dotted lines in the figure.

[0060] Figure 7 is a flowchart illustrating the characteristic operations involved in detecting the start and end points of the second tone according to this embodiment.

[0061] First, in step S11, a time-frequency analysis is performed using wavelet transform. Next, in step S12, the peak frequency of the second tone is detected using GWS calculation. Then, in step S13, the amplitude (power) waveform of the peak frequency is subjected to higher-order differentiation (third-order differentiation).

[0062] Next, in step S14, the start / end point detection unit 106 determines whether there are two positive local maxima in the second derivative. If there are none, the process moves to step S15 to perform the analysis range modification process. Specifically, it performs modification processes such as expanding the analysis range.

[0063] In response to this, if the start / end point detection unit 106 determines in step S14 that there are two positive local maxima in the second derivative, it proceeds to step S16 to determine whether the third derivative at the point in time when the second derivative takes its local maxima intersects the baseline. If it determines that there is no intersection, it proceeds to step S15. If it determines that there is an intersection, it proceeds to step S17.

[0064] In step S17, the start / end point detection unit 106 determines the relative magnitude of the two points where an intersection was detected on the time axis. For intersections with a smaller time interval, the unit moves to step S18 to set it as the start point of the second tone, and for intersections with a larger time interval, the unit moves to step S19 to set it as the end point of the second tone.

[0065] In this way, the start and end points of the second tone are detected.

[0066] <4> summary As described above, according to this embodiment, by providing a second heart sound position detection unit 101 that detects the position of the second heart sound included in the phonocardiogram, a wavelet transform unit 102 that applies a wavelet transform to the phonocardiogram of a predetermined window width including the second heart sound position detected by the second heart sound position detection unit 101, and a display unit 80 that displays a time-frequency analysis image (Figure 1B) obtained by the wavelet transform, medical professionals such as doctors can visually grasp the split state of A2 and P2 in the frequency and time directions.

[0067] Furthermore, a GWS (Global Wavelet Spectrum) calculation unit 103 is provided to perform GWS calculations on the signal after wavelet transform. By displaying the frequency power spectrum image (Figure 1C) obtained by the GWS calculation unit 103 in addition to the time-frequency analysis image (Figure 1B) on the display unit 80, medical professionals such as doctors can visually grasp the bimodal nature and peak frequencies of A2 and P2.

[0068] Furthermore, by providing a peak frequency power waveform calculation unit 104 that obtains a peak frequency power waveform (Figure 1D), which is the power waveform in the time direction of the phonocardiogram for the peak frequency of the phonocardiogram detected by GWS calculation, and a differential calculation unit 105 that differentiates the peak frequency power waveform, it becomes possible to detect the start and end points of the second heart sound included in the phonocardiogram.

[0069] The embodiments described above are merely examples of how the present invention can be implemented, and the technical scope of the present invention should not be limited by them. In other words, the present invention can be implemented in various ways without departing from its gist or its main features.

[0070] In the embodiments described above, the heart sound detection device and heart sound detection method of the present invention were described in a case where they were implemented using a blood pressure pulse wave examination device 1. However, the heart sound detection device and heart sound detection method of the present invention are not limited to this and may be implemented using a device separate from the blood pressure pulse wave examination device (for example, a personal computer).

[0071] In short, the heart sound detection device of the present invention only needs to include an acquisition unit that acquires a phonocardiogram of a subject, a second heart sound position detection unit that detects the position of the second heart sound included in the phonocardiogram, a wavelet transform unit that applies a wavelet transform to the phonocardiogram of a predetermined window width including the second heart sound position detected by the second heart sound position detection unit, and a display unit that displays a time-frequency analysis image obtained by the wavelet transform. Here, the acquisition unit that acquires the phonocardiogram may be a heart sound measurement unit 40 as in the embodiment described above, but it may also be an input unit such as an interface for inputting information on the subject's phonocardiogram. [Industrial applicability]

[0072] The present invention is widely applicable as a heart sound detection device and heart sound detection method for detecting the second heart sound from heart sounds. [Explanation of Symbols]

[0073] 1. Blood pressure and pulse wave analyzer 10. Arithmetic Processing Unit 100 Heart sound detection unit 101 Wavelet Transform Section 102 II Sound position detection unit 103 GWS (Global Wavelet Spectrum) Calculation Unit 104 Peak Frequency Power Waveform Calculation Unit 105 Differential operation section 106 Start / End Point Detection Unit

Claims

1. An acquisition unit that acquires the patient's phonocardiogram, A second heart sound position detection unit for detecting the position of the second heart sound included in the aforementioned phonocardiogram, A wavelet transform unit performs a wavelet transform on a phonocardiogram of a predetermined window width that includes the position of the second heart sound detected by the second heart sound position detection unit. A frequency analysis image obtained by applying a Global Wavelet Spectrum (GWS) operation to a signal obtained by wavelet transform, a display unit that displays the frequency analysis image showing the degree of splitting of the aortic and pulmonary artery components, A heart sound detection device equipped with the following features.

2. A peak frequency power waveform calculation unit obtains a peak frequency power waveform, which is the power waveform in the time direction of the phonocardiogram for the peak frequency of the phonocardiogram detected by the GWS calculation, A differential calculation unit that differentiates the aforementioned peak frequency power waveform, Furthermore, The heart sound detection device according to claim 1.

3. The system further includes a start / end point detection unit that uses the results of the differential calculation unit to detect the start and end points of the second heart sound included in the phonocardiogram. The heart sound detection device according to claim 2.

4. The differential calculation unit performs the third derivative on the peak frequency power waveform, The start and end point detection unit detects the start and end points of the second tone based on the third derivative result. The heart sound detection device according to claim 3.

5. The wavelet transform unit performs a wavelet transform on a phonocardiogram with a predetermined window width that includes the position of the second heart sound detected by the second heart sound position detection unit but does not include the first heart sound. The heart sound detection device according to claim 1.

6. An acquisition unit that acquires the patient's phonocardiogram, A second heart sound position detection unit for detecting the position of the second heart sound included in the aforementioned phonocardiogram, A wavelet transform unit performs a wavelet transform on a phonocardiogram of a predetermined window width that includes the position of the second heart sound detected by the second heart sound position detection unit. A display unit that displays a time-frequency analysis image obtained by wavelet transform, A GWS (Global Wavelet Spectrum) calculation unit that applies GWS calculation to the aforementioned phonocardiogram, A peak frequency power waveform calculation unit obtains a peak frequency power waveform, which is the power waveform in the time direction of the phonocardiogram for the peak frequency of the phonocardiogram detected by the GWS calculation, A differential calculation unit that differentiates the aforementioned peak frequency power waveform, A heart sound detection device equipped with the following features.

7. Steps to obtain the patient's phonocardiogram, The steps include detecting the location of the second heart sound included in the phonocardiogram, The steps include: applying a wavelet transform to a phonocardiogram of a predetermined window width that includes the detected second heart sound position; A frequency analysis image obtained by applying a Global Wavelet Spectrum (GWS) operation to a signal obtained by wavelet transform, the step of displaying a frequency analysis image showing the degree of splitting of the aortic and pulmonary artery components, A method for detecting heart sounds, including the detection of heart sounds.

8. In the step of applying the wavelet transform, the wavelet transform is applied to a phonocardiogram with a predetermined window width that includes the position of the second heart sound but does not include the first heart sound. The method for detecting heart sounds according to claim 7.

9. Steps to obtain the patient's phonocardiogram, The steps include detecting the location of the second heart sound included in the phonocardiogram, The steps include: applying a wavelet transform to a phonocardiogram of a predetermined window width that includes the detected second heart sound position; The steps include displaying the time-frequency analysis image obtained by wavelet transform, The steps include applying GWS (Global Wavelet Spectrum) calculation to the aforementioned phonocardiogram, The steps include obtaining a peak frequency power waveform, which is the power waveform in the time direction of the phonocardiogram for the peak frequency of the phonocardiogram detected by the GWS calculation, The steps include differentiating the aforementioned peak frequency power waveform, A method for detecting heart sounds, including the detection of heart sounds.

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