FR2722677A1 - Equipment for examining physiological sounds for medical purposes - Google Patents

Abstract

An acoustic sensor (3) of the stethoscope capsule type is fixed to the bottom of the case (1) and enclosed by an elastomeric skirt (6) which is suitable to make good acoustic contact with various parts of the body. Above the sensor (3) a compartment (7) houses batteries (8) and electronic circuits (9) which filter and amplify the signals from the sensor (3). Two identical loudspeakers (10) (11) are located in the top of the housing (1) mounted back to back with elastomeric interposition to eliminate feed back to the sensor (3).

Description

 The present invention relates to an auscultation device, used to detect and amplify pulsating or non-pulsating physiological noises, in particular cardiac and / or respiratory noises, and to make them audible to the naked ear, the operator being able to be at a greater or lesser distance from the person being examined.

 The object of the invention is in particular to provide an apparatus which makes it possible to detect with certainty cardiac noises, that is to say heartbeats, even through the clothing of a person and in the presence of parasitic noises, which is important in the case of accident victims requiring immediate diagnosis.

 For this kind of use, it is difficult to be satisfied with a simple stethoscope. In addition, the problem cannot be solved simply by amplifying the cardiac noises and by restoring, by a loudspeaker, the amplified cardiac noises. Indeed, there are then disturbing phenomena, in particular a "catching" as well by Larsen effect as by retransmission through the body of the device. These disturbing phenomena can be mitigated by moving the loudspeaker away from the acoustic sensor, but in this hypothesis the advantage of a compact and handy device is lost.

 The present invention avoids all these drawbacks by providing an auscultation device which, while being compact and handy, and therefore of convenient use, makes it possible to sufficiently amplify cardiac and / or respiratory noises in s' freeing from the disturbing phenomena previously mentioned, and restoring them by means of loudspeakers.

To this end, the invention relates to an auscultation device essentially comprising, in combination
- an acoustic sensor capable of being brought into contact, directly or indirectly, with a body to be examined, and delivering a corresponding electrical signal,
electronic means for amplifying and filtering the signal emitted by the sensor, and
- at least two speakers mounted in acoustic phase opposition so as to avoid the phenomena of return of vibrations towards the sensor through the body of the device itself, the speakers being, in operation, excited so simultaneously by the amplification and filtering means, and thus producing an audible sound.

 The acoustic sensor, capable of being brought into contact directly or indirectly with the body to be examined, is advantageously a membrane sensor, of the stethoscope capsule type, associated with a microphone of the electret type.

Preferably, this acoustic sensor is surrounded by a sound screen, which can be produced in the form of an annular skirt, which adapts to the morphology of the auscultated body and whose role is to acoustically isolate the sensor from ambient noise when it is applied to the body to be examined.

 According to a preferred embodiment, the monitoring device according to the invention is presented as an elongated box comprising, at one end, the sensor with its possible sound screen and provided, at its opposite end, with loudspeakers, the housing containing the electronic amplification and filtering means.

 To use the device, the sensor membrane is brought into contact with the body to be examined, for example on a patient's chest, either directly (contact with the skin) or indirectly (contact with clothing) . The sound screen, surrounding the sensor, isolates the latter from sounds coming from the rear. If the membrane is brought into contact with a body emitting or transmitting vibrations, the electret type microphone associated with it produces a corresponding electrical signal. The electrical signal is amplified, then filtered to eliminate frequencies corresponding to unwanted noise, before being reproduced by the loudspeakers, which allow anyone in the vicinity to hear it clearly.

 The particular mounting of the loudspeakers, at least two in number, makes it possible to obtain a substantially zero value for the result of the vibrations transmitted to the housing of the device, so that any retransmission of transverse vibrations through the 'device, which would risk creating a' hooking 'by feedback on the sensor, is in principle avoided. In particular, in the case of two speakers, these are identical, placed back-to-back with physical contact of their respective symmetrical reinforcement masses, so as to function in acoustic phase opposition when they are simultaneously excited by identical signals, thus the loudspeakers together produce a sufficiently powerful audible sound, without risk of snagging.

 As an additional precaution, interlayer cushions, for example made of elastomer, are provided in the housing to form phonic screens, on the one hand between the sensor and the compartment receiving the electronic amplification and filtering means, and somewhere else between this compartment and the speakers.

 The electronic amplification and filtering means comprise at least a first amplifier receiving at its input the signal from the sensor, capable of being brought into contact directly or indirectly with the body to be examined, a bandpass filter connected to the output of the first amplifier, and a final amplifier connected to the output of the bandpass filter and simultaneously driving the speakers.

 The bandpass filter eliminates extraneous noise. Advantageously, the device can include means for selecting the bandwidth of this bandpass filter, making it possible in particular to adapt the device to predefined categories of individuals, such as adult, child or fetus, for which the frequencies of heart sounds are in separate ranges.

 The device can include a headphone jack, directly connected to the output of the first amplifier, for "direct" listening to pulsed noises amplified, but not filtered, like a basic electronic stethoscope.

Advantageously, the electronic amplification and filtering means also comprise a peak detector circuit connected to the output of the bandpass filter, and associated with a "beep" generator, selection means being provided for connecting the input of the final amplifier either directly at the output of the bandpass filter, or at the output of the "beep" generator. The monitoring device thus has two modes of use
- either direct restitution, through the loudspeakers, of amplified and filtered pulsating noises, in particular cardiac noises and others
- Either generation, by the same speakers, of sound "beeps" in correspondence with the only main peaks of the cardiac pulses, selected by the peak detector circuit, the secondary peaks not being taken into account.

 The peak detector can also be connected, by means of a pulse counting circuit, to a display capable of displaying, among other things, the frequencies of the pulses, in particular of the heart.

In any case, the invention will be better understood with the aid of the description which follows, with reference to the appended schematic drawing representing, by way of nonlimiting examples, some embodiments of this auscultation device.
Figure 1 is a longitudinal sectional view of an auscultation device according to the present invention, according to a first embodiment
Figure 2 is a block diagram of the electronic circuits of this device
Figure 3 is a perspective view of another embodiment of the apparatus of the invention
Figure 4 is a diagram illustrating part of the operation of this device.

 FIG. 1 shows the physical constitution of an auscultation device in accordance with the present invention, here presented externally as an elongated casing 1 of generally cylindrical shape, the axis of which is indicated at 2.

 At one end of the housing 1, a membrane sensor 3 is provided, constituted in practice by a capsule of the stethoscope type, or a capsule made of plastic, or even rubber or elastomer or other, associated with a microphone of the electret type 4 (see also figure 2). The acoustic sensor 3 is fixed to a support piece 5, and it is surrounded by an annular skirt 6, made of elastomer or any other flexible material adapting to the contour of the auscultated part, presenting itself as a simple suction cup or multiple grooves constituting a particularly effective annular phonic screen.

 Above the sensor 3 is formed, inside the housing 1, a compartment 7 containing cells or batteries 8 for supplying electrical power to the device, and electronic circuits 9.

 The housing 1 is provided, opposite the sensor 3, with a set of two identical speakers 10 and 11, placed back to back inside a common frame 12 with the interposition of an elastomer sleeve 13.

 The apparatus further comprises an elastomer cushion 14 disposed between the support piece 5 of the sensor 3 and the electrical compartment 7, and another elastomer cushion 15 disposed between this electrical compartment 7 and the frame 12 of the speakers 10 and 11, these two cushions 14 and 15 forming complementary phonic screens.

 The embodiment of the electronic circuits 9 is illustrated, in the form of a block diagram, in FIG. 2. The microphone 4 associated with the membrane of the sensor 3 is connected to the input of an amplifier 16, the output of which is connected to a bandpass filter 17. A point between the amplifier 16 and the filter 17 is also connected to a jack 18 for headphones.

 The output of the bandpass filter 17 is on the one hand connected by a change-over contact 19, to the input of a final amplifier 20 which drives the two speakers 10 and 11. On the other hand, the output of the filter bandpass 17 is connected to a peak detector circuit 21, the output of which is connected to a "beep" generator 22 also connected, by its output, to the change-over contact 19.

 For the use of the aforementioned auscultation device, the membrane of the sensor 3 is brought into contact with the body emitting vibrations (here representing the cardiac noises). The membrane thus vibrates with this body and the microphone of the electret type 4 then produces an electrical signal in correspondence with the vibrations of the membrane. The electrical signal is amplified a first time in the amplifier 16, then this amplified signal is filtered in the bandpass filter 17 to eliminate unwanted noise, and to avoid the risks of snagging both by Larsen effect and by retransmission by the device housing 1.

 If the change-over contact 19 occupies its position shown in FIG. 2, the amplified and filtered signal is directly transmitted to the final amplifier 20, which actuates the two loudspeakers 10 and 11 placed back to back and mechanically linked by their carcasses, which thus operate in acoustic phase opposition. The cardiac noise is thus restored, in a very audible form and without causing disturbing phenomena.

 The headphone jack 18 also allows direct listening to heart sounds and other transmitted sounds, including respiratory sounds, unfiltered.

 When the change-over contact 19, controlled by a manual selector, occupies its other position, the cardiac sound is processed by the peak detector circuit 21, as illustrated by the diagram in FIG. 4.

The top line of the diagram shows the actual signal, which includes a main peak P1 and a secondary peak P2.

These two peaks P1 and P2 are quantified by integration, providing quantities Q1 and Q2 which are compared with a threshold S, suitably chosen. Only the main peak P1 gives rise to a quantity Q1 greater than the comparison threshold S, so that this main peak P1 is detected and selected.

The output signal of the peak detector circuit 21, emitted at the rate of the beating of the heart, is brought to the generator of "beep" 22 which triggers a train of pulses
T of high frequency, but of short duration. The train of pulses T is amplified in the final amplifier 20, and the speakers 10 and 11 thus emit "beeps" (brief successive sound signals) according to the heart rate.

 Figure 3 shows another embodiment of the monitoring device object of the invention, comprising a housing 1 no longer cylindrical but of different configuration, more ergonomic, provided in particular with a handle 23. The housing 1 always carries a membrane sensor 3.6 at one end, and it is also provided at its other end with two loudspeakers placed back to back, one of which 10 is here visible, while in its intermediate part the housing 1 receives the cells or batteries and the electronic circuits, the production and operation of which correspond to the preceding description.

 The box 1 again here includes a control panel 24, which may in particular include a selector 25 for sound volume, a selector 26 for the bandwidth of the filter 17, and a selector 27 controlling the reversing contact 19 "real noise / generator of" beep ", as well as a display 28 of the heart rate and possibly of visualization of a signal representing the auscultated noise (like oscilloscope). A start button 29 is advantageously placed at the free end of the handle 23.

The bandwidth selector 26 preferably has the following three positions
- "adult" position,
- "child" position,
- "fetus" position.

 The bandwidth is selected, in the electronic circuits 9, either by choosing one or the other of several bandpass filters (represented generally in the form of a single bandpass filter 17 ), or by performing equivalent digital filtering.

 As also shown in FIG. 2, the peak detector circuit 21 can also be connected to a circuit 31 for counting cardiac pulses, with digital output, itself in relation to the aforementioned display 28 which can visualize the pulses and display their frequencies.

 In a manner not shown, the device 2 can also be provided with an output, of digital or analog type, allowing its connection to external devices, in particular devices carrying out recording and / or graphical tracing.

 The auscultation device, object of the invention, can be produced as a portable device or not; it can be mounted at the end of a pole, so as to reach a person located at a distance from the operator.

As is obvious, and as is clear from the foregoing, the invention is not limited to the sole embodiments of this auscultation device which have been described above, by way of examples; on the contrary, it embraces all of the variant embodiments and applications respecting the same principle. Thus, in particular, that one would not depart from the scope of the invention
- by replacing the acoustic membrane sensor with a sensor of another suitable type, such as piezoelectric sensor, induction coil, electrostatic sensor or other, an electromagnetic sensor being in particular usable for detecting the blood mass transmitting the heartbeat;
- by producing electronic circuits in any equivalent form, either analog or digital;
- by increasing the number of loudspeakers, for example by providing three or four loudspeakers, always respecting the requirement that the result of the vibrations of the armatures of these loudspeakers is zero, in order to transmit no vibration to the body of the device and thus avoid the phenomenon of return of these vibrations to the sensor;
- by adapting the device to all physiological noises of a pulsating nature, in particular respiratory noises
- by changing the shape of the device's housing;
- by providing all provisions for the electrical supply of the device, in particular with a view to ensuring maximum autonomy
- by providing all additional functions on this device, such as sensitivity adjustment.

Claims (11)

 1. Auscultation device capable of detecting pulsating or non-pulsating physiological noises, in particular cardiac and / or respiratory noises, and making them audible to the naked ear, characterized in that it essentially comprises, in combination  an acoustic sensor (3,4) capable of being brought into contact, directly or indirectly, with a body to be examined, and delivering a corresponding electrical signal,  electronic means (9) for amplifying and filtering the signal delivered by the sensor (3,4), and  - at least two speakers (10,11) mounted in acoustic phase opposition so as to avoid the phenomena of return of vibrations towards the sensor (3,4) through the body of the device itself, these speakers (10,11) being, in operation excited simultaneously by the amplification and filtering means (9), and then producing an audible sound.  2. Auscultation device according to claim 1, characterized in that the acoustic sensor, capable of being brought into contact directly or indirectly with the body to be examined, is a membrane sensor (3), of the stethoscope capsule type, associated to an electret type microphone (4).  3. Auscultation device according to claim 1 or 2, characterized in that the aforementioned acoustic sensor (3,4) is surrounded by an annular phonic screen (6).  4. Auscultation device according to any one of claims 1 to 3, characterized in that it comprises two identical speakers (10,11), placed back to back with physical contact of their respective symmetrical armature masses , so as to operate in acoustic phase opposition when they are simultaneously excited by identical electrical signals.  5. Auscultation device according to any one of claims 1 to 4, characterized in that it is presented as an elongated housing (1) comprising, at one end, the sensor (3,4) with its possible sound screen (6) and provided, at its opposite end, with speakers (10, 11), the housing (1) enclosing the electronic amplification and filtering means (9).  6. Auscultation device according to claim 5, characterized in that intermediate cushions (14,15), for example made of elastomer, are provided in the housing (1) to form phonic screens, on the one hand between the sensor (3,4) and the compartment (7) receiving the electronic amplification and filtering means (9) and on the other hand between this compartment (7) and the speakers (10,11).  7. Auscultation device according to any one of claims 1 to 6, characterized in that the electronic amplification and filtering means (9) comprise at least a first amplifier (16) receiving at its input the signal from the sensor (3,4), capable of being brought into contact directly or indirectly with the body to be examined, a bandpass filter (17) connected to the output of the first amplifier (16), and a final amplifier (20) connected to the output of the bandpass filter (17) and simultaneously driving the loudspeakers (10,11).  8. Auscultation device according to claim 7, characterized in that it comprises a headphone socket (18), directly connected to the output of the first amplifier (16).  9. Auscultation device according to claim 7 or 8, characterized in that it comprises means (26) for selecting the passband of the bandpass filter (17).  10. Auscultation device according to any one of claims 7 to 9, characterized in that the electronic amplification and filtering means (9) also comprise a peak detector circuit (21) connected to the output of the pass filter -strip (17), and associated with a "beep" generator (22), selection means (19,27) being provided for connecting the input of the final amplifier (20) either directly to the output of the filter bandpass (17), or at the output of the "beep" generator (22).  11. Auscultation device according to claim 10, characterized in that the peak detector (21) is also connected, via a pulse counting circuit (31), to a display (28) capable of view, among other things, the pulse frequencies.