WO2001078059A2

WO2001078059A2 - Piezoelectric biological sounds monitor

Info

Publication number: WO2001078059A2
Application number: PCT/CA2001/000550
Authority: WO
Inventors: Vittorio F. Lanzo; Van Cong Nguyen
Original assignee: Andromed Inc.
Priority date: 2000-04-12
Filing date: 2001-04-12
Publication date: 2001-10-18
Also published as: WO2001078059B1; AU2001256020A1; WO2001078059A3

Abstract

The biological sounds monitor (100) comprises a piezoelectric membrane (105) and a mechanical assembly. The latter mechanical assembly includes a membrane support (101) on which the piezoelectric membrane is mounted, and a wave-propagating mechanism (108) disposed on one side of the piezoelectric membrane. Upon use of the biological sound monitor, the wave-propagating mechanism is interposed between the piezoelectric membrane and an examinee's body to propagate acoustic waves from the examinee's body to the piezoelectric membrane. Advantageously, the membrane support comprises a piezoelectric membrane tensioning mechanism.

Description

BIOLOGICAL SOUNDS MONITOR

BACKGROUND OF THE INVENTION

1. Field of the invention:

The present invention relates to a biological sounds monitor using a piezoelectric membrane.

2. Brief description of the prior art:

The stethoscope was invented in the early 1800's by a Frenchman named Rene Laenne as a solution to a delicate problem. Hitherto, physicians listened to heart sounds by pressing their ears to the patient's chest. One day, the young Dr. Laennec was examining a young woman with symptoms of heart disease. As he reported, "The patient's age and sex did not permit direct application of the ear to the chest". Being desperate, and resourceful, he rolled up a sheet of paper to form a tube, placed one end into his ear and the other against her chest. In doing so, he not only preserved her modesty but was "surprised and gratified at being able to hear the beating of her heart with much greater clearness and distinctiveness than...ever before". It took a while before this new invention was adopted by his peers, let alone improved. However, by 1852, Dr. George Cammann of New York designed the first binaural stethoscope, which not only transmitted more sound and blocked out extraneous sounds, but was also the first to resemble today's instruments.

Early stethoscopes had only a bell chest piece. This excelled at picking up low frequencies, but missed the higher frequencies. Several diaphragms were invented to address this problem with the first efficient bell/diaphragm combination with a revolving stem designed in Boston by Dr. Howard Sprague in 1926. Variations of this model became the mainstay of physicians and nurses, even today.

While it is difficult to dispute the benefits of acoustic stethoscopes, one must also accept that such stethoscopes are limited in their ability to detect, transmit and amplify sound. It is only by adding electronics technology that one can do better. An electronic stethoscope is capable of capturing more heart sounds, even faint ones which would otherwise be imperceptible by acoustic means, filtering out extraneous noise, and amplifying what's left to levels far superior to that which can be heard with acoustic stethoscopes. In fact, an electronic stethoscope is to acoustic stethoscopes what the paper tube was to Dr. Laennec.a revolution which enables the practitioner to "hear the beating of the heart with much greater clearness and distinctiveness than...ever before". The company Andromed was the first to bring an electronic stethoscope to market. Its very successful product, known under the trademark "Stethos", is presently distributed worldwide by the company Agilent.

OBJECT OF THE INVENTION

An object of the present invention is to propose a biological sound monitor for electronic stethoscopes and/or long-term monitoring using a piezoelectric membrane.

SUMMARY OF THE INVENTION

More specifically, in accordance with the present invention, there is provided a biological sounds monitor comprising a piezoelectric membrane and a mechanical assembly. This mechanical assembly comprises a membrane support on which the piezoelectric membrane is mounted, and a wave-propagating mechanism disposed on one side of the piezoelectric membrane. Upon use of the biological sounds monitor, the wave-propagating mechanism is interposed between the piezoelectric membrane and an examinee's body to propagate acoustic waves from the examinee's body to the piezoelectric membrane. The membrane support may include a piezoelectric membrane tensioning mechanism.

According to a first preferred embodiment of the biological sounds monitor:

- the piezoelectric membrane is a piezoelectric disk formed with an annular peripheral portion having a first side with a convex cross section and a second side with a concave cross section;

- the membrane support comprises:

- a cylindrical base having an annular distal edge face defining a circular groove to receive the first side of the annular peripheral portion of the piezoelectric disk;

- a sealing ring applied to the second side of the annular peripheral portion of the piezoelectric disk; and

- an annular sealing cap mounted on the cylindrical base and applied to the sealing ring on a side opposite to the annular peripheral portion of the piezoelectric disk;

- the wave-propagating mechanism comprises:

- a gel disk applied to the piezoelectric disk; and

- a flexible sensor cap having an annular peripheral portion inserted between the sealing ring and the annular sealing cap. According to a second preferred embodiment of the biological sounds monitor:

- the piezoelectric membrane is a piezoelectric cylinder, the membrane support comprises a base cup having an inner cylindrical face to which the piezoelectric cylinder is applied, and the piezoelectric cylinder is longitudinally slotted;

- the wave-propagating mechanism comprises: - a bottom, axial and inwardly tapering frusto-conical face of the base cup;

- a pressure ring having an outer annular face applied to the piezoelectric cylinder, and an inner annular face applied to the bottom, axial and inwardly tapering frusto-conical face of the base cup; and

- a pickup cap mounted axially movable on an open end of the base cup, this pickup cap comprising an outer face for application to the examinee's body and an inner, axial and inwardly tapering frusto-conical face applied to the inner annular face of the pressure ring;

- the outer annular face of the pressure ring has a flat cross section and the inner annular face of the pressure ring has a semicircular cross section; According to another preferred embodiment of the biological sounds monitor according to the present invention:

- the piezoelectric membrane is a piezoelectric disk having an annular peripheral portion, and the membrane support with piezoelectric membrane tensioning mechanism comprises:

- a cylindrical support ring with an outer cylindrical face and an annular edge face on which the annular peripheral portion of the piezoelectric disk is applied; and - a sealing ring comprising: a cylindrical flange mounted on the outer cylindrical face of the support ring; an annular, generally flat wall applied to the annular peripheral portion of the piezoelectric disk; and an inner intersection between the cylindrical flange and annular, generally flat wall which is rounded to force the annular peripheral portion of the piezoelectric disk to curl around the annular edge face of the support ring to keep the piezoelectric disk under tension;

- the wave-propagating mechanism comprises a pickup cone applied to the piezoelectric disk on the side opposite to the cylindrical support ring and peripherally retained between the annular, generally flat wall of the sealing ring and the annular edge face of the cylindrical support ring;

- the annular, generally flat wall of the sealing ring comprises an axial, central opening, and the pickup cone comprises concentric undulations exposed in the axial, central opening of the annular, generally flat wall.

In accordance with a fourth preferred embodiment of the biological sounds monitor of the invention:

- the piezoelectric membrane is a piezoelectric disk having an annular peripheral portion, and the membrane support with piezoelectric membrane tensioning mechanism comprises: - a base ring having an annular flat face, a central axial opening, and an annular groove in the annular flat face of the base ring, wherein the annular peripheral portion of the piezoelectric disk is applied to the annular flat face over the annular groove;

- a pressure ring applied to the annular peripheral portion of the piezoelectric disk on the side opposite to the annular flat face of the base ring at the level of the annular groove; and

- a flexible plate mounted on the annular flat surface and applied to the pressure ring which forces the annular peripheral portion of the piezoelectric disk in the circular groove to hold this piezoelectric disk under tension;

- the flexible plate is a clapper plate with a central clapper, and the wave-propagating mechanism comprises this central clapper.

According to a last preferred embodiment of the biological sounds monitor: the piezoelectric membrane is a piezoelectric strip having first and second opposite ends;

the membrane support with piezoelectric membrane tensioning mechanism comprises an elongated, convex spring preload superposed to the piezoelectric strip and having first and second opposite ends connected to the first and second ends of the piezoelectric strip, respectively;

the spring preload is formed with a window therein;

- the wave-propagating mechanism comprises a sensor plate superposed to the spring preload and having first and second opposite ends connected to the first and second ends of the spring preload, respectively; and

- the sensor plate comprising a semi-rigid body extending through the window of the spring preload to contact the piezoelectric strip.

The foregoing and other objects, advantages and features of the present invention will become more apparent upon reading of the following non restrictive description of a preferred embodiment thereof, given for the purpose of illustration only with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

In the appended drawings:

Figure 1 a is an exploded, perspective view of a first preferred embodiment of biological sounds monitor according to the present invention;

Figure 1b is a cross sectional, side elevation view of the first preferred embodiment of biological sounds monitor according to the present invention;

Figure 2a is a top plan view of an exemplary piezoelectric membrane used in the biological sounds monitor according to the present invention;

Figure 2b is a side elevational view of the piezoelectric membrane of Figure 2a; and

Figure 2c is the equivalent circuit of the piezoelectric membrane of Figures 2a and 2b; Figure 3a is an exploded, perspective view of a second preferred embodiment of biological sounds monitor according to the present invention;

Figure 3b is a cross sectional, side elevation view of the second preferred embodiment of biological sounds monitor according to the present invention;

Figure 4a is an exploded, perspective view of a third preferred embodiment of biological sounds monitor according to the present invention;

Figure 4b is a cross sectional, side elevation view of the third preferred embodiment of biological sounds monitor according to the present invention;

Figure 5a is an exploded, perspective view of a fourth preferred embodiment of biological sounds monitor according to the present invention;

Figure 5b is a cross sectional, side elevation view of the fourth preferred embodiment of biological sounds monitor according to the present invention; Figure 6a is an exploded, perspective view of a fifth preferred embodiment of biological sounds monitor according to the present invention;

Figure 6b is a perspective view of the fifth preferred embodiment of biological sounds monitor according to the present invention;

Figure 6c is a side elevation view of the fifth preferred embodiment of biological sounds monitor according to the present invention;

Figure 7 illustrates a biological sound monitor according to the present invention attached to an examinee's skin;

Figure 8 is a block diagram illustrating a remote monitoring application of the biological sounds monitor according to the present invention;

Figure 9 is an electronics flowchart for processing biological sounds monitor according to the present invention;

Figure 10a is the transfer function of a diaphragm mode low-pass filter used in an external noise isolating filter unit of the electronics flow chart of Figure 9; and Figure 10b is the transfer function of a bell mode low- pass filter used in an external noise isolating filter unit of the electronics flow chart of Figure 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Five (5) examples of biological sounds monitors using a piezoelectric membrane will be first described.

Example 1 :

The piezoelectric monitor 100 of Figures 1a and 1 b comprises a cylindrical base 101 of uniform thickness. On its lower, outer cylindrical face 102, the base 101 comprises a series of circular, laterally adjacent V-shaped grooves 103. In this preferred embodiment, three (3) V-shaped grooves are provided. Also, cylindrical base 101 comprises an annular distal edge face defining a circular groove 104 (Figure 1b) with an irregular cross section.

A piezoelectric disk (piezoelectric membrane) 105 has an annular peripheral portion 106 having a first side with a convex cross section shaped to fit in the groove 104 as shown in Figure 1 b. The annular peripheral portion 106 of the piezoelectric disk 105 also comprises a second side with a concave cross section. A sealing ring 107 is applied to the second side of concave cross section of the annular peripheral portion 106 of the piezoelectric disk 105 as illustrated in Figure 1a. This sealing ring 107 has a circular cross section and is made of resilient material.

A disk 108 has a flat face 109 applied to the piezoelectric disk 105 and a dome face 110 opposite to the flat face 109. This disk 108 is made of silicone bubble gel. Of course, other alternative materials could be contemplated to fabricate the disk 108.

An appropriately shaped, flexible sensor cap 111 is provided to cover the sealing ring 107 and the dome face 110 of the disk 108.

Finally, monitor 100 comprises an external, annular sealing cap 112. Cap 112 is formed with a cylindrical flange 113 with a series of, for example, three (3) circular triangular ridge protuberances 114 structured to be press fit in the circular V-shaped grooves 103. The sealing cap 112 finally comprises an annular wall 115 with a convex cross section to be applied to the annular peripheral portion 116 of the sensor cap 111 and to the sealing ring 107 through portion 116. An axial hole 117 of the external sealing cap 112 expose the central, dome-shaped portion of the sensor cap 11 1.

To assemble the monitor 100: the annular peripheral portion 106 of the piezoelectric disk 105 is placed in the circular groove 104 of the cylindrical base 101 ;

the sealing ring 107 is applied to the side of concave cross section of the annular peripheral portion 106 of the piezoelectric disk 105;

the flat face 109 of the disk 108 is applied centrally to the piezoelectric disk 105;

the sensor cap 111 is applied to the monitor 100 to cover the sealing ring 107 and the dome face 110 of the disk 108 as illustrated in Figure 1 b; and

- the external sealing cap 112 is mounted on the cylindrical base 101 by press fitting the three (3) circular triangular ridge protuberances 114 in the circular V-shaped grooves 103.

The sealing cap 112 then retains the piezoelectric disk 105, the sealing ring 107, the disk 108 made of silicone bubble gel, and the sensor cap 111 in place on the cylindrical base 101.

Operation of the monitor 100 of Figures 1 a and 1b in combination with a stethoscope will now be described. In a first step, the user grips the base 101 and sealing cap 112 with his(her) fingers. The central dome-shaped portion of the sensor cap 111 is then applied to a examinee's (patient's) body to tension the piezoelectric disk 105 through the disk 108 made of gel. Acoustic waves, including sound vibrations, are then propagated from the examinee's body to the piezoelectric disk 105 through the sensor cap 111 and the gel disk 108. These acoustic waves alter the level of tension in the piezoelectric disk 105 and thereby alter polarization of this piezoelectric disk 105 to convert these acoustic waves to a corresponding electric signal.

Indeed, as well known to those of ordinary skill in the art, a piezoelectric membrane such as 201 of Figures 2a and 2b comprises a sheet of piezoelectric material 200.

In the present case, the sheet of piezoelectric material 200 is used as a mechano-electrical transducer. In operation, the piezoelectric material becomes temporarily polarized when subjected to a physical stress and the direction and magnitude of the polarization depend upon the degree of this stress. Therefore, the piezoelectric material of the sheet 200 will produce a voltage and current, or will modify the magnitude of a current flowing through it in response to a change in the mechanical stress applied thereto. In other words, the electrical charge generated is proportional to the change in mechanical stress.

Referring back to Figures 2a and 2b, the piezoelectric membrane 201 further comprises a top electrode 202 on the top face of the sheet 200 and a bottom electrode 203 on the bottom face of that sheet 200. Detection of voltage and/or current through the piezoelectric material is obviously made through these top electrode 202 and bottom electrode 203. Figure 2c depicts the equivalent electric circuit of the piezoelectric membrane 201.

Accordingly, the stress produced by the acoustic waves in the piezoelectric membrane will produce a corresponding electric signal.

Example 2:

The piezoelectric monitor 300 of Figures 3a and 3b comprises a retaining pin 301 preferably made of plastic material and comprising a longitudinally grooved shank 302 and a flat head 303.

The monitor 300 further comprises a base cup 304 having a bottom wall 305 and a cylindrical wall 306. The cylindrical wall 306 has an inner cylindrical face 307. The bottom wall 305 has a central axial hole 308 to receive the shank 302 of the pin 301 , an outer axial and cylindrical cavity 309 to receive the head 303 of the pin 301 , an inner top flat face 310 generally perpendicular to the geometrical axis 311 of the base cup 304, and an inner, axial and inwardly tapering frusto-conical face 312 extending between the inner top flat face 310 and the bottom of the base cup 304. The shank 302 of the pin 301 is free to slide axially in the hole 308 while the flat head 303 is free to slide axially in the cylindrical cavity 309. A longitudinally slotted (see 314) piezoelectric cylinder

(piezoelectric membrane) 313 is applied to the inner cylindrical face 307.

In the preferred embodiment illustrated in Figure 3b, the axial length of the piezoelectric cylinder 313 is equal to the axial length inner cylindrical surface 307.

A pressure ring 315 has an outer annular face 316 flat in cross section and an inner annular face 317 semicircular in cross section. Face 316 applies to the piezoelectric cylinder 313 and semicircular face 317 applies to the frusto-conical face 312 of the base cup 304.

A pickup cap 318 comprises an outer circular flat face 319 and a peripheral annular flange 320 covering an annular edge portion 321 of the cylindrical wall 305 of the base cup 304. Inside the flange 320, an annular groove 322 is rectangular in cross section to receive an annular edge portion 323 of both the cylindrical wall 305 and the piezoelectric cylinder 313. Just a word to mention that the annular edge portion 323 is free to slide axially in the annular groove 322. The pickup cap 318 further comprises an inner circular flat face 324 confronting flat face 310 and perpendicular to the axis 311 , and an inner, axial and inwardly tapering frusto-conical face 325 extending between the circular flat face 324 and the annular groove 322. Finally, the circular flat face 324 has an axial, cylindrical blind hole 326 in which the longitudinally grooved shank 302 of the retaining pin 301 is press fit. To assemble the monitor 300:

- the piezoelectric cylinder 313 is placed against the inner cylindrical face 307 of the wall 305;

- the pressure ring 315 is placed in the base cup 304 with annular face 316 applied to the piezoelectric cylinder 313 and annular face 317 applied to the frusto-conical face 312 of the base cup 304;

- the shank 302 of the retaining pin 301 is inserted in the hole 308 with the flat head 303 of the same pin 301 in the cylindrical cavity 309; and

- the longitudinally grooved shank 302 of the retaining pin 301 is press fit in the hole 326 of the pickup cap 318; during this operation, the annular edge portion 323 of both the cylindrical wall 305 and the piezoelectric cylinder 313 is introduced in the annular groove 322 and the inner frusto-conical face 325 of the cap 318 is applied to the annular face 317 of the pressure ring 315.

Operation of the monitor 300 of Figures 3a and 3b in combination with a stethoscope will now be described. In a first step, the user grips the base cup 304 with his(her) fingers. The flat face 319 of the pickup cap 318 is then applied to an examinee's body. This produces a force tending to move flat face 324 toward flat face 310; this applies a pressure to the inner face 317 of the pressure ring 315 through the frusto- conical faces 312 and 325 to apply a corresponding pressure to the piezoelectric cylinder 313 through the outer face 316 of the pressure ring 315. Acoustic waves are then transmitted from the patient's body to the piezoelectric cylinder 313 through the pickup cap 318 and the pressure ring 315. These acoustic waves alter the level of tension in the piezoelectric cylinder 313 and thereby alter polarization of this piezoelectric cylinder 313 to convert these acoustic waves to a corresponding electric signal.

Example 3:

The piezoelectric monitor 400 of Figures 4a and 4b comprises a cylindrical support ring. On its upper, outer cylindrical face 402, the support ring 401 comprises a series of circular, laterally adjacent triangular ridge protuberances 403. In this preferred embodiment, three (3) triangular ridge protuberances are provided. Also, the support ring 401 comprises a distal annular edge face 404.

A piezoelectric disk (piezoelectric membrane) 405 has an annular peripheral portion applied to the annular edge face 404 of the support ring 401 as shown in Figure 4b.

A pickup cone 406 is applied to the piezoelectric disk 405 on the side opposite to the support ring 401. Cone 406 comprises a plurality of centered, concentric wave-like undulations 407. Finally, a sealing ring 408 is formed with a cylindrical flange 412 with a series of, for example, three (3) inner circular triangular ridge protuberances 410 structured and positioned to be press fit in the outer circular triangular ridge protuberances 403 of the support ring 401. The sealing ring 408 finally comprises an annular, generally flat wall 411 with an axial, central opening 409 in order to expose the concentric undulations 407 of the pickup cone 406. The annular wall 411 comprises an inner annular groove 413 adapted to receive and retain a peripheral undulation 414 of the pickup cone 406. Therefore, the annular wall is applied to the annular peripheral portion of the piezoelectric disk 405 through the pickup cone 406.

To assemble the monitor 400:

- the annular peripheral portion of the piezoelectric disk 405 is applied to the annular edge face 404 of the support ring 401 ;

- the pickup cone 406 is applied to the piezoelectric disk 405; and

- the sealing ring 408 is mounted on the support ring 401 by press fitting the three (3) inner circular triangular ridge protuberances 410 of the sealing ring 408 in the three (3) outer circular triangular ridge protuberances 403 of the support ring 401.

The sealing ring 408 then retains the annular peripheral portion of the piezoelectric disk 405 and the pickup cone 406 in place on the cylindrical support ring 401. Also, the inner intersection between the cylindrical flange 412 and the annular wall 411 is rounded whereby the sealing ring 408 forces the periphery of the piezoelectric disk 405 to curl around the edge face 404 of the support ring 401 to keep disk 405 under tension.

Operation of the monitor 400 of Figures 4a and 4b in combination with a stethoscope will now be described. In a first step, the user grips the flange 412 of the sealing ring 408 with his(her) fingers. The undulations 407 of the pickup cone 406 are then applied to an examinee's body. Acoustic waves are then transmitted from the examinee's body to the piezoelectric disk 405 through the pickup cone 406. These acoustic waves alter the level of tension in the piezoelectric disk 405 and thereby alter polarization of this piezoelectric disk 405 to convert these acoustic waves to a corresponding electric signal.

Example 4:

The piezoelectric monitor 500 of Figures 5a and 5b comprises a generally flat, base ring 501. Base ring 501 comprises an axial, central circular opening 502 bevelled on one side (see 503). On the opposite side, the base ring 501 includes an annular flat face 507 with two concentric circular grooves 504 and 505 proximate to central opening 502. A piezoelectric disk (piezoelectric membrane) 506 has an annular peripheral portion applied to the annular flat face 507 of the base ring 501 around the opening 502, over the circular groove 505, and in an annular, shallow cavity 519 formed for that purpose.

A pressure ring 508 made of resilient material is applied to the annular peripheral portion of the piezoelectric disk 506 on the side opposite to the flat face 507 at the level of the circular groove 505. As shown in Figure 5b, the pressure ring 508 is slightly wider than the circular groove 505. Also, the diameter of the pressure ring 508 is substantially the same as the diameter of the circular groove 505.

Finally, the biological sounds monitor 500 comprises a flexible clapper plate 509. The clapper plate 509 comprises a peripheral, generally flat annular portion 510 having a reversed, generally U-shaped cross section. Clapper plate 509 further comprises an inner circular groove 515 to nest the pressure ring 508.

Annular portion 510 also comprises two inwardly extending concentric, circular fastener members 511 and 512 both L- shaped in cross section and disposed back to back with respect to each other. Bevelled faces 513 and 514 give to the cross section of the fastener members 511 and 512 an arrow shape enabling the circular members 511 and 512 to be driven in the T-shaped groove 504. The L- shaped cross section of the circular fastener members 511 and 512 then hooks the T-shaped groove 504 to thereby fasten the clapper plate 509 to the side 507 of the base ring 501.

Plate 509 further comprises a central disk-shaped clapper 516 connected to the annular portion 510 through three (3) 120° spaced apart radial spokes 517. Two circular and concentric annulus 518 are also mounted on the spokes 517 between the clapper 516 and the annular portion 510 to mechanically protect the piezoelectric disk 506. As illustrated in Figure 5b, the clapper 516 has one face applied to the piezoelectric disk 506.

To assemble the monitor 500:

- the annular peripheral portion of the piezoelectric disk 506 is peripherally disposed in the annular, shallow cavity 519;

- the pressure ring is disposed in the circular groove 515 of the clapper plate 509; and

- the two inwardly extending concentric, circular fastener members 511 and 512 are driven in the T-shaped groove 504 of the base ring 501.

In this assembly, the clapper plate 509 is applied to the pressure ring 508 to apply on the pressure ring 508 a pressure which forces the piezoelectric disk 506 in the circular groove 515 of the base ring 501 to hold this piezoelectric disk 506 under tension. Operation of the monitor 500 of Figures 5a and 5b in combination with a stethoscope will now be described. In a first step, the user grips the base ring 501 with his(her) fingers. The clapper 516 is then applied to a patient's body. Acoustic waves are then transmitted from the examinee's body to the piezoelectric disk 506 through the clapper 516. These acoustic waves alter the level of tension in the piezoelectric disk 506 and thereby alter polarization of this piezoelectric disk 506 to convert these acoustic waves to a corresponding electric signal.

Example 5:

The biological sounds monitor 600 of Figures 6a, 6b and 6c comprises a piezoelectric strip 601 with partially looped opposite ends 602 and 603. Partially looped end 602 comprises a folded strip end forming a hook 616. In the same manner, partially looped end 603 comprises a folded strip end forming a hook 617.

An elongated spring preload 604 is slightly convex, is superposed to the piezoelectric strip 601 and is provided with partially looped opposite ends 605 and 606 respectively pivotally fitted in the partially looped ends 602 and 603 of the piezoelectric strip 601. As illustrated in Figure 6a, spring preload 604 comprises a central elongated rectangular window 607. The function of this spring preload 604 is to push outwards on the ends 602 and 603 of piezoelectric strip 601 in order to tension this piezoelectric strip. A semi-rigid sensor plate 608 is superposed to the spring preload 604 and comprises partially looped opposite ends 609 and 610 respectively pivotally fitted in the partially looped ends 605 and 606 of the spring preload 604. Sensor plate 608 is formed with an underside semi-rigid body 611 presenting the general configuration of a parallelepiped. Body 611 extends through the rectangular window 607 of the spring preload 604 and comprises a bottom wall 612 applied to the piezoelectric strip 601. As better shown in Figure 6b, the body 611 defines an outwardly opening cavity 615 presenting the general configuration of a parallelepiped. A central linear protuberance 613 extends from the bottom wall 612 in the cavity 615. In the same manner, a rectangular protuberance 614 extends from the bottom wall 612 and surrounds the linear protuberance 612 in the cavity 615. Both protuberances 613 and 614 have a rectangular cross section.

An elongated rectangular frame 618 has a first transversal end portion 619 hooked by hook 616, and a second transversal end portion 620 hooked by hook 617.

In operation, the spring preload 604 pushes outwards on the ends 602 and 603 of the piezoelectric strip 601 , and the semi-rigid plate 608 applies pressure to the spring preload 604 to thereby stretch and therefore tension the piezoelectric strip 601. The frame 618 pulls on the hooks 616 and 617 to safeguard the assembly integrity. Operation of the monitor 600 of Figures 6a, 6b and 6c will now be described. In a first step, the user grips with his(her) fingers the ends 602 and 603 of the piezoelectric strip 601. The semi-rigid sensor plate 608, in particular the protuberances 613 and 614, is then applied to an examinee's body. Acoustic waves then propagate from the examinee's body to the piezoelectric strip 601 through the sensor plate 608. The acoustic waves alter the level of tension in the piezoelectric strip 601 to thereby alter polarization of this piezoelectric strip 601 and convert these acoustic waves to a corresponding electric signal.

In the foregoing examples 1-5, operation of the biological sounds monitor according to the invention has been described in a stethoscope mode. However, as illustrated in Figure 7, a biological sounds monitor such as 700 can also be designed as a lightweight, disposable, reliable, non-invasive biological sounds monitor 704 that can be attached to an examinee's skin 701 via an adhesive (not shown), in a manner similar to an EKG electrode, to enable a physician to monitor the examinee's biological sounds through a stethoscope or other monitoring devices. As well known to those of ordinary skill in the art, this type of equipment is associated with a clip-on connector 702 to connect the monitor 704 to a cable 703.

Potential applications of the biological sounds monitor according to the invention are the following:

- hospital monitoring (cardio/pulmonary); - home monitoring (cardio/pulmonary);

- neo-natal (incubator) monitoring (cardio/pulmonary);

- Parkinson's monitoring;

- heart and/or respiratory monitoring during surgery;

- replacement of complex EKG (electrocardiogram) monitoring with single lead auscultation monitor;

- EMT (emergency medical technician) monitoring equipment; and

disposable attachment for electronic stethoscope.

Moreover, the biological sounds monitor can be made blue-tooth compatible for home and hospital monitoring. It can be adapted for use with competitive hospital monitoring (and telemetry) equipment, and for use with two-dimensional or three-dimensional sound.

In an exemplary remote monitoring application illustrated in Figure 8, the biological sounds monitor(s) form(s) part of a group 800 of sensors also including ECG (electrocardiogram) electrodes,

SPO2 sensors, temperature sensors, etc. The sensors 800 are connected to an emitter 801 transmitting through a RF connection 802, for example a RF bluetooth, the information from the sensors 800 to a local receiver 803. The information from the sensors 800 is then transmitted by the local receiver 803 to a server 805 through a cellular telephone 806, for example a bluetooth cellular telephone 804. The information from the sensors 800 stored in the server 805 can be made available to a central monitoring station 808, a physician 809 and/or the patient 810 through a remote access 807 communicating with the server 805 through the internet 806.

An example of electronics flowchart for biological sounds monitor according to the present invention is illustrated in Figure 9. In this flowchart:

- a biological sounds monitor 900 is piezo-based as described hereinabove and comprises a FET (field- effect transistor) buffer;

- a high-voltage patient isolation 902 electrically insulates the patient from hazardous voltage and current;

- a pre-amplifier 903 pre-amplifies the electric signal 910 from the biological sounds monitor 900; - an anti-tremor filter unit 904 withdraws from the pre- amplified signal 910 the noise caused, in particular but not exclusively, by the involuntary trembling motion of a user's hand holding the biological sounds monitor

5 900;

- an isolating filter unit 905 isolates the external noise such as speech and other ambient noise from the signal 910, this filter unit 905 using the low-pass filter of Figure

10 10a in diaphragm mode and the low-pass filter of Figure

10b in bell mode;

- an amplifier 906 amplifies the pre-amplified and filtered signal 910;

15

- an A/D converter 907 converts the analog amplified signal from amplifier 906 to a digital signal subsequently data compressed and encoded (908) before being transmitted through a data transmitter 909 (modem,

20 USB (unified S-band antenna system), serial, RF (radio frequency) modulation, etc.); and

- a power supply 901 supplies electric voltage and current to the circuit elements 900 and 902-909 of

25 Figure 9. The foregoing description does not indicate the materials of which are made the different pieces of the various embodiments of the biological sounds monitor according to the present invention. It is respectfully submitted that it is within the capacity of one of ordinary skill in the art to select these materials. Moreover, a plurality of alternatives for the material of each piece is often available.

Although the present invention has been described hereinabove by way of preferred embodiments thereof, these embodiments can be modified at will, within the scope of the appended claims, without departing from the spirit and nature of the subject invention.

Claims

WHAT IS CLAIMED IS:

1. A biological sounds monitor comprising a piezoelectric membrane and a mechanical assembly, wherein said mechanical assembly comprises;

- a membrane support on which the piezoelectric membrane is mounted; and

- a wave-propagating mechanism disposed on one side of the piezoelectric membrane and which, upon use of the biological sounds monitor, is interposed between said piezoelectric membrane and an examinee's body to propagate acoustic waves from the examinee's body to the piezoelectric membrane.

2. A biological sounds monitor as recited in claim 1 , wherein the membrane support comprises a piezoelectric membrane tensioning mechanism.

3. A biological sounds monitor as recited in claim 1 , wherein the piezoelectric membrane is a piezoelectric disk formed with an annular peripheral portion having a first side with a convex cross section and a second side with a concave cross section, and wherein the membrane support comprises:

- a cylindrical base having an annular distal edge face defining a circular groove to receive the first side of the annular peripheral portion of the piezoelectric disk; - a sealing ring applied to the second side of the annular peripheral portion of the piezoelectric disk; and

- an annular sealing cap mounted on the cylindrical base and applied to the sealing ring on a side opposite to the annular peripheral portion of the piezoelectric disk.

4. A biological sounds monitor as recited in claim 3, wherein the wave-propagating mechanism comprises:

- a gel disk applied to the piezoelectric disk; and - a flexible sensor cap having an annular peripheral portion inserted between the sealing ring and the annular sealing cap.

5. A biological sounds monitor as recited in claim 1 , wherein the wave-propagating mechanism comprises a gel disk applied to the piezoelectric membrane.

6. A biological sounds monitor as recited in claim 1 , wherein the piezoelectric membrane is a piezoelectric cylinder, and wherein the membrane support comprises a base cup having an inner cylindrical face to which the piezoelectric cylinder is applied.

7. A biological sounds monitor as recited in claim 6, wherein the piezoelectric cylinder is longitudinally slotted.

8. A biological sounds monitor as recited in claim 6, wherein the wave-propagating mechanism comprises: - a bottom, axial and inwardly tapering frusto-conical face of the base cup;

- a pickup cap mounted axially movable on an open end of the base cup, said pickup cap comprising an outer face for application to the examinee's body and an inner, axial and inwardly tapering frusto- conical face applied to the inner annular face of the pressure ring.

9. A biological sounds monitor as recited in claim 8, wherein the outer annular face of the pressure ring has a flat cross section and the inner annular face of the pressure ring has a semicircular cross section.

10. A biological sounds monitor as recited in claim 2, wherein the piezoelectric membrane is a piezoelectric disk having an annular peripheral portion, and wherein the membrane support with piezoelectric membrane tensioning mechanism comprises:

- a cylindrical support ring with an outer cylindrical face and an annular edge face on which the annular peripheral portion of the piezoelectric disk is applied; and

- a sealing ring comprising: - a cylindrical flange mounted on the outer cylindrical face of the support ring; - an annular, generally flat wall applied to the annular peripheral portion of the piezoelectric disk; and

- an inner intersection between the cylindrical flange and annular, generally flat wall which is rounded to force the annular peripheral portion of the piezoelectric disk to curl around the annular edge face of the support ring to keep the piezoelectric disk under tension.

11. A biological sounds monitor as recited in claim 10, wherein the wave-propagating mechanism comprises:

- a pickup cone applied to the piezoelectric disk on the side opposite to the cylindrical support ring and peripherally retained between the annular, generally flat wall of the sealing ring and the annular edge face of the cylindrical support ring.

12. A biological sounds monitor as recited in claim 11 , wherein:

- the annular, generally flat wall of the sealing ring comprises an axial, central opening; and - the pickup cone comprises concentric undulations exposed in said axial, central opening of the annular, generally flat wall.

13. A biological sounds monitor as recited in claim 2, wherein the piezoelectric membrane is a piezoelectric disk having an annular peripheral portion, and wherein the membrane support with piezoelectric membrane tensioning mechanism comprises: - a base ring having an annular flat face, a central axial opening, and an annular groove in the annular flat face of the base ring, wherein the annular peripheral portion of the piezoelectric disk is applied to the annular flat face over the annular groove; - a pressure ring applied to the annular peripheral portion of the piezoelectric disk on the side opposite to the annular flat face of the base ring at the level of the annular groove; and

- a flexible plate mounted on the annular flat surface and applied to the pressure ring which forces the annular peripheral portion of the piezoelectric disk in the circular groove to hold said piezoelectric disk under tension.

14. A biological sounds monitor as recited in claim 13, wherein the flexible plate is a clapper plate with a central clapper, and wherein the wave-propagating mechanism comprises said central clapper.

15. A biological sounds monitor as recited in claim 2, wherein the piezoelectric membrane is a piezoelectric strip having first and second opposite ends, and wherein the membrane support with piezoelectric membrane tensioning mechanism comprises:

- an elongated, convex spring preload superposed to the piezoelectric strip and having first and second opposite ends connected to the first and second ends of the piezoelectric strip, respectively.

16. A biological sounds monitor as recited in claim 15, wherein the spring preload is formed with a window therein, and wherein the wave-propagating mechanism comprises:

- a sensor plate superposed to the spring preload and having first and second opposite ends connected to the first and second ends of the spring preload, respectively, said sensor plate comprising a semi-rigid body extending through the window of the spring preload to contact the piezoelectric strip.