KR20010081039A - Sound pickup sensor - Google Patents

Abstract

The sensor 10 for use with the electronic stethoscope 15 is preferably tightly engaged with the hard back piece 1 and converts one or two piezoelectric foils 4, which convert piezoelectric members, for example sound pressure, into electrical signals. A substantially cylindrical viscoelastic contact and transfer body 20 enclosed tightly by 7).

Description

Sound capture sensor {SOUND PICKUP SENSOR}

Stethoscopes based on auditory principles are already known and widely used. Conventional hearing stethoscopes with added electronic amplification are also known. Underwater hydrophones, which record sounds from animals underwater, are known from biological studies in marine animals. These techniques form the background of the present invention and these techniques can be understood in the following manner.

Conventional stethoscopes are based on sound transmitted through air and various types of hoses or tubes. This is associated with the transmission of sound waves from body tissues into the air. Compression of air is detected in the listener's ear. Sometimes there is a diaphragm at the tip of the device, but still delivery to the air takes place. An example of this type of technology is the so-called Litman stethoscope.

Conventional stethoscopes are sometimes equipped with microphones for capturing and electronically amplifying sounds carried by air. Even in this case, sound is transmitted from the tissue to the air and from the air to various types of microphone sensors. Manufacturers of such stethoscopes are, for example, Littman and Ariel, and there are also Japanese manufacturers.

Applicant has already produced a stethoscope transducer with pins or pegs of hard material in direct contact with the skin, in which sound is transmitted directly from the body tissues through the pegs of hard material into the sensor.

In addition, hydrophones are known which capture underwater sounds from animals, strata and mechanical products. Such hydrophones cannot be used for diagnostic purposes both inside and outside the living body for humans and animals.

Ultrasonic instruments are widely used in the diagnostic field, and these instruments mainly make a kind of viscous contact with the skin. However, viscous contact is typically made by a kind of gel, ie a gel that does not form part of the device itself and is applied to the skin before placing the device on the skin.

U. S. Patent No. 4,672, 976, filed by Kroll, discloses a means for placing on a patient's body to listen to heart sounds and to detect low frequency sound waves. This means has a flexible diaphragm in direct contact with the skin and adapted to body contours. The housing of this means is filled with a fluid, which contains a hydroacoustic unit inside the fluid. A feature of the Kroll means is to always provide good coupling into the hydrophone by minimizing the acoustic difference between the material in the listening means and body tissues. It is also important that the fluid surrounding the hydrophone is a bubble-free liquid medium, i.e., "a hydrophone gel".

Kroll is also a co-inventor of US Pat. No. 4,947,859 to Brewer et al., Which further refines the idea described above. In US Pat. No. 4,947,859, acoustic transducers are further developed, using polymer materials instead of liquid solutions or gels around sensor units centrally placed in a "puck" -like device that can be placed on the patient's skin. The polymeric material is substantially acoustically adapted to body tissue. The above two patents clearly teach that it is already known to use adaptation materials intended to mimic body tissue for acoustic properties. However, this adaptation cannot go further. Sensor units embedded in bulk polymers will be affected by sounds from everywhere, for example, which will not have any directivity or amplification capability. Listening means, such as the Brewer, are soft enough to fit the body. This is not advantageous in terms of bonding in some cases where there is a part with, for example, a rigid diaphragm that is in close contact with the skin. Brewer et al. Are designed to perform signal processing outside of the "puck," and the listening device configuration does not provide the ability to block electrical noise radiated inside.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stethoscope, and more particularly, to a sensor for capturing a sound generated in an animal or a human body and converting it into an electrical output signal. The invention also relates to a complete electronic stethoscope.

1 is a view showing an example of a viscoelastic unit constituting a sensor unit according to the present invention.

2 shows a back piece designed for a viscoelastic unit of FIG.

Figure 3 is an exploded view clearly showing the parts included in the sensor as an embodiment of the sensor according to the present invention.

4 shows the same embodiment of the sensor shown in FIG. 3 mounted into a stethoscope module.

The present invention has been made to solve the problems of the prior art as described above. Thus, according to a first aspect of the invention, an acoustic-electric transducer member for converting sound vibrations into an electrical output signal, and is arranged as an adaptation medium between the body surface and the transducer member, with the front face directly facing the body surface. A sensor is provided that captures sound from the body, including a viscoelastic unit. In this sensor, the acoustic-electric transducer member consists of at least one piezoelectric member that tightly surrounds the side of the viscoelastic unit, the viscoelastic unit has a cylindrical shape, and the viscoelastic unit has a hard back piece in the rear end region. tightly meshes with (back piece)

In one embodiment of the invention, the acoustic transducer member consists of two coaxially arranged piezoelectric foils interposed with an electrically conductive foil. This intermediate electrically conductive foil may consist of a double sided adhesive electrically conductive tape.

In one embodiment, the piezoelectric foil may consist of a flat foil laid around the viscoelastic unit in such a way that adjacent ends are fixed by adhesive tape. As another way, the piezoelectric foil is cylindrical and can be tightly fitted on the viscoelastic unit.

In another embodiment of the sensor, the acoustic transducer member may be composed of a ceramic ring having a piezoelectric effect.

In a preferred embodiment of the invention, the back piece and the viscoelastic unit in the rear end region have an exactly complementary shape that includes a substantially conical and forward pointing interface.

The sensor described above can be suitably used as a sensor element of an electronic stethoscope.

In another embodiment of the present invention, there is provided an electronic stethoscope comprising a headset having an earphone with a loudspeaker, a portable sound capture module having a sensor element and an electronic amplifier circuit, and a connection wiring between the module and the headset. Is the sensor as defined by the sensor element in the most general manner above.

For example, sounds produced in a natural way in the human body are mostly pressure fluctuations in tissues that contain water. Sound is produced in various organs and is caused by the movement, contraction, and expansion of each organ in addition to the fluid flow in the body. These sounds are scattered through the body, and the frequencies measured at specific locations will depend on both the various attenuation and amplification possibilities and sound sources inside the body. The object of the viscoelastic sensor according to the invention is to transmit sound waves from the body directly through the acoustic adaptation / conversion medium into the built-in sensor element / acoustic transducer unit, in such a way that the sound pressure is evenly distributed in the sound receiving region of the transducer member. To the transducer member. In addition, it is intended to widen the range of audible sounds as much as possible and to minimize attenuation within the transducer element.

The above design is clearly different from all known sensor systems in which sound is transmitted through the air, and distinctly from the sound receiving area from the body being contacted through a much larger peg. The present invention is also distinguished from ultrasound-type devices that operate at frequencies well beyond the limits that viscoelastic sensors can handle, and ultrasound systems use gels in a completely different way to provide contact with the skin as described above.

In addition, since the main features of the present invention consist of very different geometrical features, they are distinguished from sound transmission in viscous elements as disclosed in the US patents belonging to Kroll / Brewer et al.

Unlike conventional hydrophones that receive sound pressure from the outside, the viscoelastic sensor acts as an internal transmission medium, and this viscoelastic sensor differs from hydrophones in that it has a much better chance of being offered for a stethoscope, i.e. greater Provides the possibility of the area being isolated from sound transmission.

In addition, exemption to external sounds is one of the important ideas that form the basis for generating the present invention. In the event of an accident or emergency, many external disturbance sounds can be caused by machines, engines, calls, etc., so that it may be difficult for a doctor to perform a diagnosis by stethoscope. Due to the high impedance of the viscoelastic sensor, external sounds carried by air are attenuated. This helps the doctor to focus on sounds from the body. This feature cannot be found in conventional stethoscopes or stethoscopes having diaphragms based on microphones or associated with a peg arrangement.

Immunity to the "accelerometer effect" is another new feature. The isocentrical design of the sensor isolates mechanical vibrations due to the manipulation or operation of the viscoelastic sensor. Acceleration in the direction of the voltage response will induce an opposing force on the sensing element, thereby causing a voltage with the opposite polarity and in this way attenuating the noise signal.

Good isolation from external electromechanical devices is of great importance with regard to the reduction of noise that can interfere with diagnostic functions. This is also a novel feature of the viscoelastic sensor according to the invention compared to conventional hydrophones.

Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In order to look at a specific embodiment according to the present invention in more detail, first with reference to FIG. 1 shows a side view and a plan view of a compact body 2 of cylindrical shape. The cylindrical body 2 has an inner hole / cavity with an opening formed from the bottom. The shape of the hole / cavity is a shape completely complementary to the top shape of the back piece 1 to be described later shown in FIG. At the top, the cylindrical body 20 is finished with an almost planar or slightly arcuate surface, which surface is for receiving sound from the body region. Most of the cylindrical body 2 consists almost of the same type of viscoelastic material 20, with the preferred material 20 being rubber. That is, the cylindrical body 2 is preferably made of cast rubber, preferably silicone rubber.

2 shows a back piece 1 designed to work with the cylindrical body 2. The hard back piece 1 has a base portion 12 in the form of a plate at its bottom / back, and a narrow neck portion 13 protrudes upward from the plate, and this neck portion 13 is formed. Silver supports a larger head portion. All these parts / parts of the back piece 1 are shaped cylindrically and coaxially, but the tip / top part of the head part has the shape of a conical surface 11.

By inserting the head portion with the conical tip 11 into the cavity of the cylindrical body 2, the rubber mass 20 in such a way that the viscoelastic material 20 closely engages the entire surface with respect to the back piece 1. ) Will tight around the head and narrow portion 13.

The back piece 1 is preferably made of metal and is formed in one piece. The most important characteristic of the back piece 1 is that it can provide a uniform sound pressure to the surrounding acoustic-electric transducer member (not specifically mentioned so far). This is also why the shape of the top / front of the back piece is conical. In addition to the negative reflection properties, ie the fact that the material is hard, the back piece, at least the substrate 12, is metalized to provide the advantage of having an excellent shielding property against electromagnetic radiation towards the actual transducer element and its signal wiring. It is preferable to prepare.

3 is an exploded view of an example of the design of the sensor unit according to the present invention. The two upper parts 1, 2 are the parts described with reference to FIGS. 2 and 1. The next part is a double-sided adhesive tape 3, which is not essential but can improve the adhesion of the outer piezoelectric foil 4. The outer piezoelectric foils 4 are shown in this example as rectangular sheets of suitable length, placed tightly around the adhesive tape 3 or directly on the viscoelastic body 2 and held tight to each other by the adhesive tape 5. The sensor foil 4 constitutes the acoustic-electric converter member of the sensor, and usually has a thin signal wire (not shown) attached to the inside and the outside.

The present embodiment is based on the use of two piezoelectric foils, so that there is an electrically conductive tape 6 on the outside of the foil 4, and this conductive tape 6 is also preferably a double-sided adhesive tape. The conductive tape 6 provides electrical contact between the second piezoelectric foil 7 disposed outside the tape 6 and the outside of the inner piezoelectric foil 4. The adhesive tape 8 keeps the edges of the foil 7 facing each other in the same way that the tape 5 traverses the opening of the foil 4.

Reference numeral 9 denotes a symbolic circuit connected to the inside and outside of one of the piezoelectric foils, which collects and processes the signal voltage from the foil. In this example, in order to use the signal from the two foils 4, 7 the signal wiring must actually be led inside the foil 4.

The piezoelectric foils 4, 7 shown are represented in the example of FIG. 3 as a rectangular "sheet" curled in a cylinder. However, it is also possible to use cylindrical foils, in which case the cylindrical foils must fit tightly outside the viscoelastic body 2. This behavior can be rather difficult.

The present invention can also accommodate other types of acoustic-electric transducers in addition to piezoelectric foils. Another preferred transducer type is a piezoceramic ring, which is made of a ceramic material and is slightly harder than a foil, but generates the same principle, the difference in voltage between the inside and the outside under the influence of pressure from the inside. It works according to the principle.

4 is a cross-sectional view of a stethoscope sensor module 15 which is a portable instrument used by a physician to detect directly from the skin or tissue surface of a patient. The sensor part 10 shown in the exploded view in FIG. 3 is a sensor housing 16 of the sensor module in such a way that a substantially flat surface in front of the viscoelastic body 2 can, for example, engage the skin surface to capture sound pressure fluctuations. ) To form a central portion mounted inside. Reference numeral 17 denotes a main body or handle portion of the sensor module 15, reference numeral 18 generally indicates an electronic circuit for signal processing and amplification of the sensor module, and reference numeral 19 generally indicates a switch and a warning lamp.

The mode of operation of the viscoelastic sensor consists in capturing sound waves from tissue or skin in front of the viscoelastic body 2, whereby sound is transmitted into the viscoelastic / viscotic medium 20. In the viscoelastic medium 20, sound energy generates a variable or operating pressure toward the inside of the acoustic-electric transducer members 4, 7, which causes mechanical tension (stress) in the transducer members 4, 7, Generate electrical voltage directly. This voltage change then generates the same frequency and phase as the sound wave. The generated alternating voltage is a signal that can be amplified, shaped, filtered and modulated in various ways in the electronic circuit 18, and can be simply transferred or handled to other electronic devices.

The sensor according to the present invention has been disclosed in a form that can be used in a stethoscope for a typical human diagnostic activity. The contact area for capturing sound waves from the body can be formed as desired by determining the diameter of the sensor body 2. Diagnostic activities may also be performed in accordance with embodiments of the present invention using a piezoceramic transducer member having a highly sensitive medium surrounding the viscoelastic silicone material. By slightly modifying the construction and materials, the same concept can be applied to both stethoscopes and instruments located inside the body. The sensor's operating range is 20 ㎐-22, and can be extended to 0 ㎐-30 ㎑ for special purposes.

Claims (10)

An acoustic electric transducer member (4. 7) for converting sound vibrations into an electrical output signal, and A viscoelastic unit 2 arranged as an adaptation medium between the body surface and the transducer members 4, 7, with the front face directly facing the body surface In the sensor to capture the sound from the body, including; The acoustic-electric transducer member is composed of at least one piezoelectric member 4, 7 which tightly surrounds the side of the viscoelastic unit, The viscoelastic unit 2 has a cylindrical shape, The viscoelastic unit is tightly engaged with the hard back piece (1) in the rear end region. A sound capture sensor according to claim 1, wherein said acoustic transducer member is comprised of at least one thin piezoelectric foil (4, 7). The sound capture sensor according to claim 2, wherein the acoustic transducer member is composed of two coaxially arranged piezoelectric foils (4, 7) interposed with an electrically conductive foil (6). The sound capture sensor according to claim 3, wherein the intermediate electrically conductive foil consists of a double-sided adhesive electrically conductive tape (6). The sound capturing sensor according to claim 2, wherein the piezoelectric foil consists of a flat foil placed around the viscoelastic unit in such a manner that adjacent ends are fixed by an adhesive tape. The sound capturing sensor according to claim 2, wherein the piezoelectric foil (s) is cylindrical and fits tightly on the viscoelastic unit. The sound capture sensor according to claim 1, wherein said acoustic transducer member is composed of a ceramic ring having a piezoelectric effect. 8. The back piece (1) and the viscoelastic unit (2) according to any one of the preceding claims, having an exactly complementary shape comprising an interface that is substantially conical and pointing forward. Having a sound capture sensor. A method of using the sensor according to any one of claims 1 to 8 as a sensor element of an electronic stethoscope. An electronic stethoscope comprising a headset having an earphone with a loudspeaker, a portable sound capturing module 15 having a sensor element 10 and an electronic amplifier circuit 18, and a connection wiring between the module 15 and the headset. In The sensor element 10 An acoustic electric transducer member (4. 7) for converting sound vibrations into an electrical output signal, and A viscoelastic unit (2) arranged as an adaptation medium between the body surface and the transducer members (4, 7) with the front face directly facing the body surface It is a sensor that captures the sound from the body, including The acoustic-electric transducer member is composed of at least one piezoelectric member 4, 7 which tightly surrounds the side of the viscoelastic unit, The viscoelastic unit (2) has a cylindrical contour, and the viscoelastic unit (2) is tightly engaged with the hard back piece (1) in the rear end region.