Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B7/00—Instruments for auscultation
  • A61B7/02—Stethoscopes
  • A61B7/04—Electric stethoscopes

Definitions

• the present invention relates to auscultation, and in particular the invention relates to a sensor for picking up sound generated in an animal or human body, including conversion to an electrical output signal.
• the invention also relates to a complete electronic stethoscope.
• stethoscopes are sometimes supplemented with microphones picking up the airborne sound in order to amplify it electronically. In this case there is also a transmission of sound from the body tissue to air, and from the air to various types of microphone sensors. Examples of manufacturers of such stethoscopes are Littman and Ariel, and there are also Japanese manufacturers.
• the present applicant has previously produced a stethoscope transducer with a pin or peg of a hard material that is brought to direct contact with skin, in such a manner that sound is transferred directly from the body tissue through the hard peg material and into the sensor.
• hydrophones for picking up sound in water from animals, ground formations and machine constructions are well known. Such hydrophones cannot be used for diagnostic purposes in connection with humans and animals, neither inside nor outside a living body.
• Ultrasound tools are utilized to a large degree within the field of diagnosis, and these tools often use a type of viscous contact toward the skin.
• the viscous contact is usually constituted by a type of gel, i.e. a gel that does not constitute part of the tool itself, however a gel that is applied to e.g. the skin prior to placing the tool in toward the skin.
• the sensor unit imbedded in the bulk polymer will for instance be influenced by sound from everywhere, and it will not have any directivity or amplification ability.
• the listening means of Brewer et al is so soft that it can be shaped after the body where it is desirable. This is not an advantage in any connection, in some cases there is a point to having e.g. a rigid diaphragm in close engagement with the skin. Brewer et al are dependent on making signal processing outside "the puck", and the listening device construction provides no screening against inward radiated electrical noise.
• a sensor for picking up sound from a body comprising an acoustoelectric transducer member for converting sound vibrations to electrical output signals, and a viscoelastic unit arranged as an adaptation medium between a body surface and the transducer member, and in such a manner that a front surface of the visco- elastic unit is arranged to be brought to direct engagement with the body surface.
• the sensor is characterized in that the acoustoelectric transducer member is constituted by at least one piezoelectric member surrounding tightly the lateral surface of the viscoelastic unit, the viscoelastic unit having a cylindrical outer shape, and that the viscoelastic unit engages tightly in its rear end area a hard back piece.
• the acoustic transducer member is constituted by two concentrically arranged piezoelectric foils, possibly having an electrically conductive foil therebetween.
• Such an intermediate electrically conductive foil may be constituted by a double-sided adhesive and electrically conductive tape.
• the piezoelectric foil can be constituted by a flat foil laid around the viscoelastic unit in such a manner that adjacent edges are fixed by an adhesive tape.
• the piezoelectric foil may have a cylindrical shape, and can be threaded tightly onto the viscoelastic unit.
• the acoustic transducer member is constituted by a ceramic ring with a piezoelectric effect.
• the back piece and the viscoelastic unit have in the rear end area precisely complementary shapes comprising an interface that is substantially conically shaped and pointing in a forward direction.
• the sensor defined above finds a favorable use as a sensor element in an electronic stethoscope.
• an electronic stethoscope comprising a head set with ear phones having loudspeakers, a hand- held sound pick-up module with a sensor element and electronic amplifier circuitry, as well as a connection lead between the module and the headset, and this electronic stethoscope is characterized in that the sensor element is a sensor such as defined in the most general manner above.
• Sounds produced in a natural manner e.g. in a human body, are pressure variations in tissue that mostly contains water. Sound arises in various organs and their movements, compressions, expansions as well as from fluid streams in the body. These sounds are scattered through the body, and frequencies measured in a certain place will depend both on the sound source and the various attenuation and amplification possibilities found inside the body.
• the purpose of the viscoelastic sensor in accordance with the invention is to transfer the sound waves from the body and into a built-in sensor element/acoustoelectric transducer unit directly through an acoustical adaptation/transformation medium and to the very transducer member in such a manner that sound pressure is distributed uniformly over the sound receiving area of the transducer member. Besides, it is attempted to minimize attenuation and to achieve as wide a range of audible sounds as possible, into the transducer member.
• a design as just mentioned differs clearly from all previously known sensor systems in which sound is transmitted through air, and it differs clearly from contact through a peg, in that the area for sound reception from the body is much larger.
• the invention is also distinguished from ultrasound type devices that operate with frequencies far beyond what the viscoelastic sensor is able to deal with, and the ultrasound systems utilize a gel in a quite different manner to provide contact against the skin, such as previously mentioned.
• the invention also is distinguished from sound transmission in viscous elements such as indicated in the US patents belonging to Kroll/Brewer et al, since critical features of the invention are constituted by very different geometrical features. It is to be noted that such a viscoelastic sensor differs from hydrophones in the fact that whereas traditional hydrophones receive a sound pressure from its outside, the present viscoelastic sensor operates with an internal transmission medium, so that better possibilities are provided for stethoscopic use, in that a larger area is isolated for sound transmission. Furthermore, immunity toward external sounds is one of the important ideas that have formed a basis for generating the present invention.
• Immunity to an "accelerometer effect” is another novel feature. Isocentrical design of the sensor provides isolation against mechanical vibrations due to handling or operation of the viscoelastic sensor. An acceleration force in a direction causing a voltage response, will also induce an opposite force to the sensing element and thereby result in a voltage having the opposite polarity, and in this manner the noise signal is attenuated.
• fig. 1 shows an example of a viscoelastic unit constituting part of a sensor in accordance with the invention
• fig. 2 shows a back piece designed to be adapted to the viscoelastic unit in fig. 1
• fig. 3 shows an embodiment of a sensor in accordance with the invention, in an exploded view to show clearly the parts included in the sensor
• fig. 4 shows the same embodiment of the sensor as shown in fig. 3, mounted into a stethoscope module.
• Fig. 1 shows a compact body 2 having a cylindrical outer shape, in a side view and in a view from above.
• the cylinder body 2 has an inner bore/cavity with an opening from the bottom side.
• the shape of the bore/cavity is quite comple- mentary to the shape of the top sections of the back piece 1 appearing in fig. 2, which back piece is to be discussed more thoroughly below.
• the cylinder body 2 ends with a substantially plane or somewhat arcuate surface, which surface is the intended reception surface for sound from a body area.
• the bulk part of the cylinder body 2 is constituted substantially by a homogenous and viscoelastic material 20, the preferred material 20 being rubber, i.e. the cylinder body 2 may preferably be made of cast rubber, preferably silicone rubber.
• the hard back piece 1 designed to cooperate with the cylinder body 2.
• the hard back piece 1 has a base part 12 in the form of a slab, and protruding upward from the slab a narrowed neck-like part 13 which in its turn supports a head part having a larger diameter. All these parts/ sections of back piece 1 are shaped cylindrically and coaxially, but at the front/top end the head part has the shape of a conical surface 11. It appears clearly that by forcing the head part with its conical tip 11 into the cavity in the cylinder body 2, the rubber mass 20 will snap in place around the head part and the narrowed part 13, in such a manner that close engagement is achieved for the viscoelastic material 20 against the back piece 1 along all surfaces.
• the back piece 1 is preferably made of metal, and constructed as an integral body.
• the most important quality of the back piece 1 is that it is able to provide a uniform sound pressure to a (so far not mentioned in particular) surrounding acoustoelectric transducer member. This is a reason behind the conical shape of the top/forward part of the back piece.
• sound reflecting characteristics i.e. the fact that the material is hard, it is favorable to have good screening characteristics against electromagnetic radiation in toward the actual transducer member and its signal leads, and it is therefore preferable to manufacture the back piece of metal, at least base part 12.
• fig. 3 appears, in an exploded view, an example of a design of a sensor part in accordance with the invention.
• the two top parts 1 and 2 are the parts just mentioned in connection with figs. 2 and 1.
• the next part is a double-sided adhesive tape 3 that is not necessary, but may provide an improved attachment for an external piezoelectric foil 4, in the example shown a rectangular sheet with adapted length, to be laid tightly around adhesive tape 3 or directly onto visco- elastic body 2, and which is held tight together using a piece of adhesive tape 5.
• the sensor foil 4 constitutes the acoustoelectric transducer member of the sensor, and is normally equipped with thin (not shown) signal leads attached to inside and outside.
• the embodiment appearing here is based on the use of two piezoelectric foils, and outside foil 4 there is therefore an electrically conductive tape 6, which is preferably also a double-sided adhesive tape.
• the conductive tape 6 provides electric contact between the outside of the inner piezoelectric foil 4 and a second piezoelectric foil 7 that is placed outside tape 6.
• An adhesive tape 8 holds the edges of foil 7 in toward each other, in the same manner as tape 5 across the opening of foil 4.
• Reference numeral 9 indicates a symbolized circuit connected to the in- and outside of one of the piezoelectric foils, for collecting and processing signal voltages from the foil.
• a signal wire should also lead to the inside of foil 4, in order to make use of a signal from both foils 4 and 7.
• cylindrical foils which must then be threaded tightly outside the viscoelastic body 2. This operation may be a little difficult.
• the invention also accommodates other types of acoustoelectric transducers than piezoelectric foils, and another preferred transducer type is a piezoceramic ring, which is somewhat more rigid than a foil, since it is made from a ceramic material, but operating in accordance with the same principle, i.e. by generating a voltage difference between in- and outside when there is a pressure influence from the inside.
• FIG. 4 appears a section through a stethoscope sensor module 15, which is the hand-held instrument used by a doctor for sensing directly from the skin or tissue surface of a patient.
• a sensor part 10 of the type appearing exploded in fig. 3 is a central part mounted inside the sensor housing 16 of the sensor module, in such a manner that the forward, substantially flat surface of the viscoelastic body 2 can be made to engage e.g. the skin surface to pick up sound pressure variations.
• Reference numeral 17 refers to a hand grip part or a main body for sensor module 15, numeral 18 refers generally to electronic circuitry for signal processing and amplification in the module, while switches and warning lamps are generally indicated by reference numeral 19.
• the operating mode of the viscoelastic sensor consists in picking up sound waves from the tissue or skin in front of viscoelastic body 2, whereby sound is transmitted into the viscoelastic/viscous medium 20.
• the sound energy creates a variable or dynamic pressure toward the inside of the acoustoelectric transducer member 4, 7, and the pressure results in a mechanical tension (stress) in transducer member 4, 7, which in its turn generates electrical voltage directly.
• the voltage change then takes place with the same frequency and phase as the sound wave.
• the alternating voltage generated is the signal that can be amplified, shaped, filtered and modified in various manners in the electronic circuits 18, in such a manner that it is simple to handle or transfer to other electronic devices.
• the present sensor has been described in a form that can be utilized in a stethoscope, for ordinary diagnostic activity on human bodies.
• the contact area for picking up sound waves from the body can be shaped as desired, by deciding the diameter of the sensor body 2.
• the diagnostic activity can also be carried out with an embodiment of the invention utilizing a piezoceramic transducer member having medium to high sensitivity surrounding a viscoelastic silicone material. With small variations in configuration and materials, the same concept can be implemented both for use in stethoscopes and for use in instruments to be placed inside the body.
• the operating range of the sensor is in the sound range 20 Hz- 22 kHz, with an extension option to a range 0 Hz-30 kHz for special purposes.

Landscapes

• Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Public Health (AREA)
• Heart & Thoracic Surgery (AREA)
• Medical Informatics (AREA)
• Molecular Biology (AREA)
• Surgery (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Engineering & Computer Science (AREA)
• Veterinary Medicine (AREA)
• Biomedical Technology (AREA)
• Piezo-Electric Transducers For Audible Bands (AREA)
• Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
• Measuring And Recording Apparatus For Diagnosis (AREA)
• Electrophonic Musical Instruments (AREA)
• Force Measurement Appropriate To Specific Purposes (AREA)
• Details Of Audible-Bandwidth Transducers (AREA)
• Measuring Fluid Pressure (AREA)
• Cable Accessories (AREA)
• Bidet-Like Cleaning Device And Other Flush Toilet Accessories (AREA)
• Signal Processing Not Specific To The Method Of Recording And Reproducing (AREA)
• Fire-Detection Mechanisms (AREA)
• Fittings On The Vehicle Exterior For Carrying Loads, And Devices For Holding Or Mounting Articles (AREA)

Priority Applications (13)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Cited By (3)

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Citations (2)

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• 1998
  • 1998-12-03 NO NO19985642A patent/NO306926B1/no not_active IP Right Cessation
• 1999
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  • 1999-12-01 BR BR9916920-7A patent/BR9916920A/pt not_active IP Right Cessation
  • 1999-12-01 JP JP2000587670A patent/JP4571311B2/ja not_active Expired - Fee Related
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  • 1999-12-01 MX MXPA01005455A patent/MXPA01005455A/es unknown
  • 1999-12-01 DE DE69918713T patent/DE69918713T2/de not_active Expired - Lifetime
  • 1999-12-01 WO PCT/NO1999/000361 patent/WO2000035348A1/en not_active Ceased
  • 1999-12-01 AU AU16988/00A patent/AU765702B2/en not_active Ceased
  • 1999-12-01 EA EA200100738A patent/EA002963B1/ru not_active IP Right Cessation
  • 1999-12-01 CN CNB998139726A patent/CN1172632C/zh not_active Expired - Fee Related
  • 1999-12-01 AT AT99960042T patent/ATE270845T1/de not_active IP Right Cessation
  • 1999-12-01 EP EP99960042A patent/EP1135063B1/en not_active Expired - Lifetime
  • 1999-12-01 ES ES99960042T patent/ES2226473T3/es not_active Expired - Lifetime
  • 1999-12-01 PL PL99348020A patent/PL348020A1/xx unknown
  • 1999-12-01 US US09/856,569 patent/US7082202B1/en not_active Expired - Fee Related

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