JP2003102725A - Stethoscope and sound input part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a comfortably usable stethoscope capable of easily and effectively suppressing external noise and unnecessary vibration to obtain clear and accurate auscultatory sound, and to provide a sound input part therefor. SOLUTION: This stethoscope has an input transducer 1 for inputting the sound from a human body; an input transducer 2 disposed close to the input transducer 1, at a position not allowing entrance of the sound from the human body, and allowing input of sound having high correlation with the external noise inputted to the input transducer 1; a processing part 200 processing a signal from the input transducer 1 on the basis of a signal from the input transducer 2 by an algorithm of adaptive prediction type active noise control; and a reproduction part 300 outputting the sound from the human body on the basis of a signal from the processing part 200.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stethoscope that suppresses external noise and unnecessary vibration during auscultation by a stethoscope and enables clear auscultation and long-term use, and a sound input section thereof.

[0002]

2. Description of the Related Art A stethoscope has been developed as a tool for doctors to obtain information about a patient's medical condition from acoustic information. In particular, stethoscopes are easier to carry and operate than other medical devices, and are widely used as the simplest and most effective devices. Conventionally, these stethoscopes include a passive type that does not have an electrical amplification mechanism and a general electronic stethoscope that has an electrical amplification mechanism.

The passive type is most widely used at present and is composed of a chest piece 21, an ear tube 22, and an ear tip 23, as shown in FIG. The chest piece 21 has a diaphragm type and an open bell type. In the diaphragm type, as shown in FIG. 17, the bottom surface of the diaphragm 24 is applied to the surface of the body, and the vibration of the body is transmitted to the bottom surface of the diaphragm 24 and propagates through the cavity. In the open bell type, as shown in FIG. 18, the open bell is applied to the surface of the body, and the vibration of the body propagates through the cavity. The ear tube 22 is for propagating the sound obtained by the chest piece 21, and the ear tip 23 is inserted into the ear canal to listen and auscultate the sound propagating through the ear tube 22. Thus, with a passive stethoscope,
No electrical processing is done in the path, all controlling the acoustics by their physical structure and shape.

On the other hand, the electronic stethoscope, as shown in FIG. 19, has an input transducer such as a microphone somewhere on the path from the portion corresponding to the chest piece of the passive stethoscope to both ears of the stethoscope. 41 is installed. Then, in order to listen to the input sound, the output transducer 42 such as earphones or headphones is used. In these electronic stethoscopes, the input transducer 41 is used to convert sound or vibration into an electric signal, and the amplifier 4
Amplify by 3. The amplified electric signal is processed by using the equalizer 44 or the like, and is amplified by the drive amplifier 45 so that the output transducer 42 can be driven. Further, the sound is converted into sound through the output transducer 42 and reproduced in both ears of the stethoscope, so that the stethoscope performs auscultation.

[0005]

However, the above-mentioned conventional passive type stethoscope and electronic stethoscope have the following problems. That is, in the passive type stethoscope that is often used in the present situation, by inserting the ear tips into both ears and closely contacting each other, the sound propagating through the ear tube from the chest piece does not leak, and I try not to hear the noise from the outside. However, if the sound inside the human body picked up by the chest piece does not reach the sound pressure that can be heard by the stethoscope, the stethoscope cannot hear the desired sound. In addition, since the ear tips are inserted in close contact with the ear canals of both ears, pressure and pain may be generated in the ear canals, which makes continuous use for a long time difficult.

On the other hand, in a general electronic stethoscope, sound is electrically amplified on the path from the input transducer to both ears, and when reproducing to both ears, earphones or headphones are used instead of ear chips. Since such an output transducer is used, the above problems are unlikely to occur.

However, in the modern social environment, many devices are operating everywhere for the convenience of life. On the other hand, these devices also cause noise, and in the modern society, there are many environments surrounded by noise. Under the present circumstances, not only in passive stethoscopes, but also in general electronic stethoscopes, sound picked up by the chest piece or a portion corresponding to it is added to external noise such as environmental sound around the stethoscope. When the unwanted vibration is included and is larger than the sound from the human body, it is difficult for the stethoscope to properly hear the sound of the human body and perform proper auscultation. In particular, the electronic stethoscope electrically amplifies the sound emitted from the human body, so that it also amplifies external noise.

The present invention has been proposed in order to solve the problems of the prior art as described above, and its purpose is to easily and effectively suppress external noise and unnecessary vibration, and to provide a clear and accurate An object of the present invention is to provide a stethoscope which can obtain auscultation sound and can be comfortably used, and an acoustic input section thereof.

[0009]

In order to achieve the above-mentioned object, the acoustic input section of the stethoscope according to the invention of claim 1 comprises:
A first input means for inputting sound from a human body;
And a second input means arranged in the vicinity of the input means, which is capable of inputting a sound having a high correlation with external noise entering the input means and which does not receive a sound from a human body. . In the invention according to claim 1 as described above, a sound suitable for suppressing the external noise by the adaptive predictive active noise control is generated from the sound obtained from the first input means with a simple structure by the second structure. It can be obtained from the input means.

According to a second aspect of the present invention, the sound input section of the stethoscope includes first input means for inputting sound from a human body,
A third input unit which is arranged in the vicinity of the first input unit and which is capable of inputting a sound having a high correlation with an unwanted vibration that enters the third input unit and which does not receive a sound from a human body. Characterize. In the invention according to claim 2 as described above, with a simple configuration, from the sound obtained from the first input means,
A sound suitable for suppressing the influence of unnecessary vibration can be obtained from the third input means by the adaptive predictive active noise control.

A stethoscope according to a third aspect of the present invention provides a signal from the acoustic input section according to the first or second aspect and the first input means from the second or third input means. And a sound output unit that outputs the sound from the human body based on the signal from the processing unit. Stethoscope. In the invention according to claim 3 as described above, of the sounds input from the first input means, the effects of external noise and unnecessary vibration are suppressed, and only the sound of the human body is output from the sound output unit. It is possible to hear the human body sound clearly and accurately even under such conditions as it is, and it is not necessary to use ear tips unlike the passive type, it is free from the feeling of strangeness and pressure of the external auditory meatus and it can be used for a long time it can.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Representative embodiments of the present invention will be described with reference to the drawings. Adaptive Predictive Active N
The noise control and the unnecessary vibration are actively suppressed by using the noise control (hereinafter referred to as ANC). Here, ANC is a system that superimposes sounds of the same amplitude and opposite phase on noise, and performs noise control.
The adaptive prediction type ANC is a method of performing control by predicting a future waveform of noise reaching a control point.

[1. Configuration of Embodiment] [1-1. Overall Configuration] First, the configuration of the present embodiment will be described. That is, in the present embodiment, as shown in FIG. 1, a chest piece unit 100 that picks up sound, a processing unit 200 that receives an output from the chest piece unit 100, and performs processing, and a stethoscope who receives the processed sound. It is configured by the reproducing unit 300 that reproduces with both ears. Hereinafter, each of these parts will be described in detail. [1-2. Configuration of Chest Piece Section] As the chest piece section 100, as shown in FIGS. 2 and 3, a chest piece 101 for external noise or a chest piece 102 for unnecessary vibration can be used. As shown in FIG. 2, the chest piece 101 for external noise is configured in a housing 101a having a mortar-shaped space at the opening at the tip.

An input transducer 1 for converting the sound from the human body into an electric signal is arranged at the apex of the mortar-shaped space. It also detects external noise,
An input transducer 2 for converting external noise into an electric signal is provided at an appropriate place and position where the sound from the human body is not detected. As the input transducers 1 and 2, for example, a microphone or the like can be used. The tip portion of the casing 101a is covered with the plastic film 4 like the diaphragm type chestpiece of the passive stethoscope. Further, the input transducers 1 and 2 have amplifiers 8 for amplifying respective outputs,
9 are connected, and the gains of these amplifiers are determined from the perceptual ease of listening.

On the other hand, the chest piece 102 for unnecessary vibration
As shown in FIG. 3, the chestpiece 1 for external noise is
Housing 102a, input transducer 1, similar to
It has a plastic film 4 and amplifiers 8 and 9. Further, in the unwanted vibration chest piece 102, the input transducer 3 (microphone or the like) that converts the vibration information having a high correlation with the unwanted vibration reaching the input transducer 1 into an electric signal has a close mechanical coupling with the input transducer 1. Are arranged so that the sound from the human body is not detected.

[1-3. Configuration of Processing Unit] Processing Unit 200
As shown in FIG. 4 and FIG. 5, each has an ADC (analog-digital converter) 10, 11, a DSP (digital signal processor), and a DAC (digital-analog converter). The ADCs 10 and 11 are means for converting an analog signal input from the chest piece unit 100 into a digital signal. DSP12 is A
It is a means for performing processing by an adaptive predictive active noise control algorithm, which will be described later, on the digital signals from the DCs 10 and 11, and outputting them. As shown in FIG. 6, the DSP 12 has a modeling delay Z- ^m , an adaptive filter W, and an LMS, and the function of each part will be described by the operation. The DAC 13 is means for converting the digital signal from the DSP 12 into an analog signal and inputting it to the reproducing section.

[1-4. Configuration of Playback Unit] Playback Unit 300
Is a drive amplifier 14, as shown in FIGS.
The output transducer 15 is provided. The drive amplifier 14 is means for amplifying the signal processed by the processing unit 200 in order to drive the output transducer 15. The output transducer 15 is means for converting the amplified electric signal into sound reproduced in both ears of the stethoscope, and an earphone, a headphone or the like can be used. This allows the stethoscope to hear the sound inside the human body.

[2. Operation of Embodiment] The operation of the present embodiment having the above-described configuration is as follows. First, the chest piece 101 or the chest piece 10
When an auscultation of a patient or the like is performed by using 2, the sound from the human body is converted into an electric signal by the input transducer 1, and external noise is input by the input transducer 2 or the influence sound of unnecessary vibration is input by the input transducer 3.
Is converted into an electric signal by. These signals are amplified by the amplifiers 8 and 9, respectively, and the ADCs 10 and 11 are amplified.
Is converted into a digital signal and input to the DSP 12.

The DSP 12 processes the two input signals in accordance with the adaptive predictive active noise control algorithm described below, removes the influence of external noise from the signal obtained by the input transducer 1, and removes the effect from the human body. Reproduce the sound. That is, as shown in FIG. 7, the input 1 from the input transducer 1 side is the modeling delay Z
^It is input to ^-m and output with a fixed delay. The input transducer 2 or the input 2 from the input transducer 3 side is output after being convoluted with the adaptive filter W. Then, the output of the adaptive filter W is subtracted from the output of the modeling delay Z ^−m , and the DSP 12
Is output from. The adaptive filter W is updated by the following LMS update equation 1 using the inputs 2 and e. In this equation 1, Wn is the filter coefficient of the current adaptive filter W, and Wn + 1 is the filter coefficient of the future. m
yu is the step size parameter and e is the difference between the two signals.

[0020]

## EQU00001 ## Wn + 1 = Wn + 2.times.myu.times.e.times.input 2 Equation 1 By this Equation 1, W is updated so that e is as small as possible. Here, when the input 1 is a signal that combines the sound inside the human body and the external noise, and the input 2 is the external noise or the unnecessary vibration sound, e is reduced by updating W. That is, acoustic information highly correlated with external noise and unwanted vibrations picked up by the input transducer 1 due to its geometrical arrangement is acquired by the input transducer 2 and the input transducer 3, and this acoustic information is adaptively predicted active. By applying it to a noise control algorithm, the sound inside the human body can be highlighted.

DSP 1 which is the result of the above processing
The output signal from 2 is converted into an analog signal by the DAC 13. The converted analog signal is amplified by the drive amplifier 14, converted from an electric signal to sound by the output transducer 15, and reproduced by both ears of the stethoscope. As a result, the stethoscope can receive the acoustic information from the human body among the acoustic information that has reached the input transducer 1.

[3. Effect of Embodiment] According to the present embodiment as described above, of the sound input from the input transducer 1, external noise is suppressed, only the sound of the human body is amplified, and the sound is output from the output transducer 15. Since it is not necessary to use an ear tip and the feeling of discomfort and pressure of the ear canal is released, it can be used for a long time.

Further, by using the input transducers 2 and 3 arranged close to the input transducer 1 and the adaptive predictive active noise control algorithm, the influence of external noise and unnecessary vibration is effectively suppressed, and the acoustic noise of the human body is reduced. Only can be amplified. For this reason, it becomes possible to hear the human body sound clearly and accurately under noise, which has been difficult to auscultate in the past. In particular, since the arrangement structure of the input transducers 2 and 3 in the chest piece portion 100 can obtain only information highly correlated with external noise and unnecessary vibration, it is easy to introduce an adaptive predictive active noise control algorithm. , Its effect is also improved.

[4. Other Embodiments] The present invention is not limited to the above-described embodiments, and includes the following other embodiments. For example, in the second embodiment shown in FIG. 8, the sensors S described in the above embodiments are arranged at equal intervals on a flat surface such as the mat M of the bed, and the patient lies down on the flat surface for auscultation. It is what
In this case, the sensor S may be arranged so as to be embedded in the mat of the bed, or may be provided so as to be embedded in the sheet or the like laid on the bed. In this embodiment, the processing unit A cancels the clothes shift sound or the like generated on the bed by the patient, and sends it to the reproduction unit B.

According to this embodiment, the patient can be auscultated simply by laying it on a bed or a futon, and the patient's body can be turned over as in the case of using one sensor. There is no need to perform auscultation and the burden on the patient is eliminated. In addition, since it is possible to pick up data at a plurality of points on the patient's body at the same time, a more accurate medical examination can be performed by observing the relationship between the data at these points. Further, if the reproducing unit is connected to a data monitoring device or the like, there is an advantage that the condition of the patient can be constantly monitored even if the examiner is not on the patient's side.

In the third embodiment shown in FIG. 9, the chestpiece section C having the built-in sensor and processing section is connected to the reproducing section B via a communication device such as an infrared communication port D. According to this embodiment, the auscultation sound collected by the chest piece portion C and freed from noise and unnecessary vibration is transmitted to the reproduction portion B via the infrared communication port D. In this case, the collected auscultatory sound can be transmitted not only to the reproducing unit B connected to the infrared communication port D by wire but also to the other reproducing units Ba and Bc having the infrared communication port Da. , Auscultation sounds can be heard simultaneously by multiple examiners.

[0027]

EXAMPLE A system was constructed based on the present invention, and an experiment was conducted to verify the sound deadening effect. [1. Chestpiece used in the experiment] An electret condenser microphone was used as each input transducer used in the chestpiece. The chestpiece used is equipped with an auxiliary microphone in addition to the microphone that picks up the auscultatory sound. The purpose of this is to reduce the influence of unnecessary vibration other than auscultation sound, external noise, etc., and it functions as an auxiliary sensor for appropriately picking up such information.

Here, in order to verify that these auxiliary sensors work effectively as a stethoscope by introducing adaptive signal processing, two types of chestpieces were prototyped and tested. 10 (a) and 10 (b) are layout diagrams of the microphones, and FIG. 11 is a system configuration diagram. Main microphone for collecting auscultation sound Mic. 1 in the vicinity of the microphone Mic. 2 is installed at an appropriate place and position for sensing incoming noise, and the parts other than the sound collecting part are covered with a sound insulating material (pat) (FIG. 10).
(A)). For the purpose of picking up only unnecessary vibration information, a special microphone Mic. Which completely covers the electret condenser microphone with a sound insulating material and shields sound waves entering the diaphragm. 3 was prototyped. This is the main microphone Mic. They were placed close to each other so that the mechanical coupling was close (FIG. 10 (b)). This makes it possible to obtain the vibration information associated with the mechanical vibration entering the main microphone from this auxiliary microphone in good correlation.

[2. External Noise Suppression Experiment] In order to reduce the influence of external environmental noise during auscultation, the above-mentioned FIG.
A basic experiment was performed using an adaptive digital filter for the microphone output from the chest piece shown in. [2-1. Experimental procedure and conditions] In order to imitate the human body, an experimental box with a built-in woofer was created in consideration of sound insulation characteristics. A medical silicon sheet was placed on the measurement surface, and the 2ch signal from the prototype chestpiece placed on it was input to the adaptive filter. In this experiment, pink noise was reproduced from the loudspeaker inside the box, and external noise was 1/3 oc centered at 800 [Hz].
t. Band noise was used. The specific experimental conditions are as follows. Sound source used: Pink Noise External noise: White Noise System: Modeling Delay zm:
256 [taps] Length of W: 512 [taps] Step size parameter: 0.05 Moreover, the connection diagram of each part is shown in FIG. DSP of processing unit
A computer for recording and an amplifier for headphones as a reproducing unit are connected to.

[2-2. Results and Analysis] FIG. 13 shows a result of suppressing external noise when the adaptive filter is operated. In FIG. 13, the control off curve is the output of the system when the adaptive predictive active noise control algorithm is not used. This is the output obtained with a conventional stethoscope. On the other hand, Control
The on curve is the output of the system when the adaptive predictive active noise control algorithm is operated. It can be seen that the external noise is properly suppressed.

That is, the external noise is suppressed by the operation of the adaptive filter, and the desired signal in the noise-free state is S /
It was confirmed that N could be extracted well. In addition, it was suggested that this adaptive processing had a great effect on the auditory sense, and that the diagnostic sound could be heard clearly.

[3. Experiment of suppressing the influence of unnecessary vibration] Next,
A basic experiment was performed using an adaptive digital filter for the microphone output from the chest piece shown in FIG. 10B above, mainly for the purpose of removing the influence of unnecessary vibration. [3-1. Experimental procedure and conditions] The experimental procedure is the same as the above-described experiment for suppressing external noise. Specific experimental conditions are
It is as follows. Measurement sound source: Pink Noise System: Modeling Delay z-m:
128 [taps] Length of W: 128 [taps] Step size parameter: 0.0002 FIG. 14 shows a connection diagram. A digital recorder for recording, an FFT analyzer for analysis, and an amplifier for headphones are connected to the multi-channel SR filter which is the processing unit.

[3-2. Results] FIG. 15 shows the results obtained by processing the 2ch signals from the prototype chest piece and removing unnecessary vibration components. In this experiment, Control off
It can be confirmed that the unnecessary vibration in the vicinity of 50 [Hz] generated in the curve No. 2 is suppressed by about 20 [dB] in the Control on curve.

[4. Conclusion) From the measurement data in the above experiment, even when the conventional passive type stethoscope and electronic stethoscope are difficult to auscultate due to external noise and unnecessary vibration, information that is highly correlated with external noise and unnecessary vibration is obtained. , It is shown that the suppression effect that enables auscultation can be expected by performing adaptive predictive active control using the obtained information.

[0035]

As described above, according to the present invention, external noise and unnecessary vibration can be easily and effectively suppressed to obtain a clear and accurate auscultatory sound, and a stethoscope which can be comfortably used. A sound input can be provided.

[Brief description of drawings]

FIG. 1 is an external view showing a configuration example of an embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a chest piece for external noise in the embodiment of FIG.

FIG. 3 is a schematic sectional view showing a chest piece for unnecessary vibration in the embodiment of FIG.

FIG. 4 is a block diagram showing a circuit configuration example of the embodiment of FIG.

5 is a block diagram showing a processing unit of FIG. 4. FIG.

6 is a diagram showing adaptive predictive active noise control by the DSP of FIG. 4;

FIG. 7 is a block diagram showing a processing unit of FIG.

FIG. 8 is an explanatory diagram showing another embodiment of the present invention.

FIG. 9 is an explanatory diagram showing another embodiment of the present invention.

FIG. 10 is a layout view of microphones used in an example of the present invention.

FIG. 11 is a configuration diagram of a system used in an example of the present invention.

FIG. 12 is a connection diagram of an external noise suppressing system used in an example of the present invention.

FIG. 13 is a diagram showing external noise suppression data according to the embodiment of the present invention.

FIG. 14 is a connection diagram of the unnecessary vibration suppressing system in the embodiment of the present invention.

FIG. 15 is a diagram showing unnecessary vibration suppression data according to the example of the present invention.

FIG. 16 is an external view showing an example of a conventional passive stethoscope.

17 is a sectional view showing a diaphragm type chestpiece in the stethoscope of FIG.

FIG. 18 is a cross-sectional view showing an open bell type chest piece in the stethoscope of FIG. 16.

FIG. 19 is a block diagram showing an example of a conventional electronic stethoscope.

[Explanation of symbols]

1, 2, 3, 41 ... Input transducer 4 ... Plastic film 8, 9, 43 ... Amplifier 14,45 ... Drive amplifier 15, 42 ... Output transducer 21, 101, 102 ... Chest piece 22 ... Ear tube 23 ... Eartip 24 ... Diaphragm 44 ... Equalizer 100 chest piece 101a, 102a ... Housing 200 ... Processing unit 300 ... Playback section

Continued front page    (72) Inventor Haruo Hamada             2-2-16 Sekimae, Musashino City, Tokyo (72) Inventor Noriyuki Hanawa             United States California             Star city william rain 16

Claims (3)

[Claims] 1. A first input means for inputting a sound from a human body, and a sound from the human body capable of inputting a sound in the vicinity of the first input means and having a high correlation with external noise entering the first input means. And a second input means arranged so that the sound input section does not enter the sound input section of the stethoscope. 2. A first input means for inputting a sound from a human body, and a sound from the human body which is in the vicinity of the first input means and which is capable of inputting a sound having a high correlation with an unwanted vibration entering the first input means. And a second input means arranged so that the sound input section does not enter the sound input section of the stethoscope. 3. The adaptive predictive active system according to claim 1 or 2, wherein the signal from the first input means is based on the signal from the second or third input means. A stethoscope comprising: a processing unit that processes by a noise control algorithm; and a sound output unit that outputs a sound from the human body based on a signal from the processing unit.