AU2021107209A4 - Stethoscope - Google Patents

Abstract

A stethoscope comprising a chestpiece connected to at least one eartip by at least one annular tube, the annular tube comprising a circumferential wall defining a central void wherein the central void extends along a length of the tube, the 5 circumferential wall having one or more voids formed therein. 17991857_1 (GHMatters) P113762.AU.1 25/08/21 C0 C) coo r14

Description

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STETHOSCOPE

Technical Field

Embodiments relate to a stethoscope and features of a stethoscope.

Background

A stethoscope is a device used by medical professionals for auscultation, the practice of listening to the internal sounds of a body usually animal or human, and on occasion, mechanical. There are now different types of stethoscope available including digital stethoscopes, but this disclosure is primarily concerned with acoustic stethoscopes.

D In general principle, the acoustic stethoscope operates by picking up pressure vibrations at a patient's skin and transferring those as sound waves to a users' ears through a hollow tube. The portion of the stethoscope which is placed on the patient's skin is referred to as the 'chestpiece' and there are two different types. A first type, often referred to as a 'bell' includes a hollow bell-shaped chestpiece which forms a resonant chamber to amplify the disturbances created at the patient's skin.

A second type includes a bell with a diaphragm stretched across the bell opening. The diaphragm picks up and amplifies the pressure vibrations at the user's skin. Some diaphragms are arranged with a flexible attachment to the bell so that they are tunable: by varying the pressure exerted on the back of the chestpiece a o user is able to vary the frequency response characteristics of the diaphragm. If the user presses harder, the diaphragm tends to respond to higher frequencies and if the user lessens the pressure on the back of the chestpiece, the diaphragm responds to lower frequencies.

The bell is generally more responsive to lower frequencies than the ?5 diaphragm and is used for paediatric patients, for difficult to access sites and for auscultation where lower frequencies are more desirable, for example in carotid assessment.

The sound waves are transmitted from the chestpiece through a hollow tube to hollow eartips which are inserted into the user's ears. The hollow tube therefore places the user's ear in direct communication with the chestpiece so that sound may travel uninterrupted from the chestpiece to the ear.

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Summary of the Disclosure

Insulated Tube

An embodiment provides a stethoscope comprising a chestpiece connected to at least one eartip by at least one annular tube, the annular tube comprising a circumferential wall defining a central void wherein the central void extends along a length of the tube, the circumferential wall having one or more voids formed therein.

The voids in the circumferential wall may provide sound insulation for the central void. This may prevent sound interference when a user is using the stethoscope which may, in turn, provide for a more accurate and easy to use stethoscope.

The annular tube may be ring-shaped. The tube may be substantially circular or oval in cross-section. The tube may be flexible.

The central void may extend along an entire length of the tube.

The circumferential wall in which the one or more voids are formed may be an outer circumferential wall.

The voids formed in the circumferential wall may extend through an entire circumference of the tube. The voids in the circumferential wall may extend along a length of the tube. In an embodiment, the voids in the circumferential wall extend the entire length of the tube.

?0 The voids in the circumferential wall may define an outer wall and an inner wall. In an embodiment, one or more ribs join the circumferential wall to the outer wall. The ribs may provide support to retain the voids when the tube flexes. Where there is more than one rib, the ribs may be equidistantly dispersed over a circumference of the circumferential wall. In an embodiment, there are four ribs ?5 spaced substantially at right angles to one another.

The stethoscope may have more than one central void extending along a length of the tube. Where there are two central voids, this may create two tubes which both extend between the chestpiece and respective eartips.

In an embodiment, the one or more voids formed in the circumferential wall may be filled with air or with an insulating material. The insulating material may be

17991857_1 (GHMatters) P113762.AU.1 25/08/21 one of more of mineral wool, cellulose, natural fibres, foam etc.

Modular Chestpiece

A chestpiece for a stethoscope comprising a trunk for connection to a stem, the trunk having a bottom, and a base connected to the bottom of the trunk so that, in use, the base collects sound when in contact with a patient and the sound is transmitted via the trunk and the stem to a user wherein, the base comprises a retainer for retaining a diaphragm in place and a cover defining at least a portion of a visible surface of the chestpiece.

The trunk, retainer and cover may be separate pieces which are connected D together to form the chestpiece. The trunk, retainer and cover may connect together by means of a snap-fit connection and/or a threaded interface.

Since there are separate parts to the chestpiece and, since the chestpiece is handled manually, it is the visible surfaces, particularly of the trunk and upper surface of the base, which may receive the most wear. Having separate pieces therefore may help to facilitate maintenance and upkeep.

The cover may be made from a different material to the trunk. The cover may be made from metal and the cover may be made from one or more of: a plastic such as ABS; wood, metal etc.

In an embodiment, the cover is manually removable and may be interchanged D by a user.

The retainer may further comprise an overmould to retain a diaphragm.

A void may be formed in the base. A void may help with sound insulation. In particular, since the user may handle the chestpiece using the base, the rubbing of the user's hand on the base may transfer sound through the chestpiece and ?5 attached tube to the user's ears, interfering with the sounds that the user seeks to distinguish.

The void formed in the base may be an annular void between the retainer and the cover.

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Diaphragm Adjustment

A chestpiece for a stethoscope comprising a housing and a flexible adaptor for engaging a diaphragm to the housing, wherein the flexible adaptor comprises a region of weakness proximate a point of engagement with the diaphragm.

The region of weakness may provide greater response for tuneable diaphragms. The region of weakness may increase the elastic suspension of the diaphragm which may facilitate the piston-like motion that causes amplification and thereby potentially helping to achieve maximum vibration velocity.

Where a user uses manual pressure to tune the diaphragm, the flexible region D may allow a greater range of diaphragm tautness, thereby potentially providing a diaphragm which may be tuned to a greater range of frequencies than one which lacks such a region of weakness, in particular potentially for sounds having lower frequencies.

The region of weakness may allow flex of the diaphragm relative to the housing.

The region of weakness may be annular. The diaphragm may be round.

In an embodiment, the diaphragm is retained in the chestpiece by a flexible adaptor, the flexible adaptor having an attachment for engaging with the diaphragm and an anchor for engaging with the chestpiece, and a flexible join joining the anchor D and the attachment, wherein the flexible join is more flexible than the attachment or the anchor.

The flexible adaptor may be formed as a single unit and may be moulded. The flexible adaptor may be formed as an overmould. The attachment, flexible join and anchor may be integral with one another. The flexible join may be formed by a ?5 portion having a smaller cross section than either the attachment or the anchor.

The flexible join may be made from a material having a lower Young's modulus than the material forming the attachment and/or the anchor.

In an embodiment, the attachment is formed as an overmould onto the diaphragm, the anchor is formed as an overmould onto the attachment and the flexible join is a region of relative weakness formed in the attachment. The diagraph, attachment and anchor may be formed from different materials.

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A movement of the flexible region may be movement in a direction which stretches or loosens the diaphragm during use of the chestpiece. The movement may be in a direction which stretches the diaphragm and movement in a direction which loosens the diaphragm during use of the chestpiece.

Multifrequency

A chestpiece for a stethoscope comprising a housing and a connector for engaging a diaphragm to the housing wherein the connector comprises a tuning mechanism for altering a tension in the diaphragm by stretching and relaxing the diaphragm, wherein the connector further comprises a user control for setting the D tuning mechanism to thereby allow the user to select a predetermined tension for the diaphragm.

The predetermined tension may be fixed. In this embodiment, the tension, once selected by a user does not vary significantly except under the influence of sound.

The user control may be a dial or a switch. In a further embodiment, the chestpiece may comprise a body and the user control may comprise rotating the body or a portion of the body.

The chestpiece may comprise a base and the dial may be located at a circumference of the base.

D The dial may be indexed. In an embodiment, the dial may have three different indices.

The tuning mechanism may comprise a plunger attached to the dial so that rotation of the dial causes stretching of the diaphragm.

The tuning mechanism may further comprise a flexible retainer for retaining ?5 the diaphragm in position wherein the plunger causes flex of the flexible retainer. The plunger may engage the flexible retainer. The plunger may instead, or in addition, engage the diaphragm.

The tuning mechanism may comprise a projection which engages with the diaphragm on operation of the user control. Engagement of the projection with the diaphragm may cause stretching of the diaphragm. The tuning mechanism may comprise two or more projections wherein a first projection prevents vibration in at

17991857_1 (GHMatters) P113762.AU.1 25/08/21 least a portion of the diaphragm and a second projection causes stretching of at least a portion of the diaphragm.

Rotation of the dial in a first direction may cause raising of the plunger and rotation of the dial in the opposite direction may cause lowering of the plunger.

A further embodiment extends to a chestpiece for a stethoscope comprising a housing and a connector for engaging a diaphragm to the housing wherein the connector comprises a tuning mechanism for preventing vibration in at least a portion of the diaphragm, wherein the connector further comprises a user control for setting the tuning mechanism to thereby allow the user to select a degree of D engagement between the projection and the diaphragm. The projection may be moveable with respect to the diaphragm.

Description of the Drawings

Embodiments are herein described, with reference to the accompanying drawings in which:

Figure 1 is an illustration of a stethoscope;

Figure 2 is a schematic cross-section of a tube of a stethoscope according to an embodiment;

Figure 3 is a perspective cross-section of a chestpiece of a stethoscope ?0 according to an embodiment;

Figure 4 is a side view of the cross-section of Figure 3;

Figure 5 is a cross-section of a chestpiece of a stethoscope according to an embodiment and detail of the cross-section;

Figure 6 is a schematic cross-section of a chestpiece of a stethoscope ?5 according to an embodiment in a first position;

Figure 7 illustrates the chestpiece of Figure 6 in a second position; and

Figures 8 and 9 are schematic illustrations of a chestpiece according to a further embodiment.

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Detailed Description of Specific Embodiment

Insulated Tube

Figure 1 illustrates a stethoscope 10. The stethoscope 10 comprises two eartips 12 and 14 connected by respective ear tubes 16 and 18 to a main tube 20. As illustrated, the main tube 20 bifurcates into separate left 22 and right 24 branches which receive the respective ear tubes 16 and 18.

The main tube 20 is connected to a stem 26 which is, in turn, connected to a chestpiece 28.

Figure 2 illustrates a cross-section through the main tube 20. The main tube D 20 has a central void 30 which runs along the entire length and in both the left branch 22 and right branch 24. Surrounding the central void 30 is a circumferential wall 32 which forms the outer surface 34 of the main tube 20.

Two voids 36 and 38 are formed in the circumferential wall 32. The voids 36 and 38 are separated by two ribs 40 and 42. In this embodiment, voids 26 and 38, and the ribs 40 and 42 extend the length of the main tube 20 including the left branch 22 and right branch 24.

The voids 36 and 38 define an outer wall 44 and an inner wall 46. The ribs 40 and 42 extend between the outer wall 44 and the inner wall 46.

It is to be realised that variations are possible too. For example, there may be ?0 fewer or more than two voids formed in the circumferential wall. Furthermore, the ribs may not extend the entire length of the main tube. Instead one or more of the ribs may extend a part of the length of the main tube, in which case at certain cross sections, the void formed in the circumferential wall may extend over the entire circumference of the main tube.

?5 In these embodiments. the left branch 22 and right branch 24 will have the same cross-sections as illustrated in Figure 2, in this embodiment. In a variation, left branch 22 and right branch 24 have independent tubes carrying the sound from the chestpiece. In these embodiments, the main tube below the branch into left and right will have a central void comprised of two tubes (the left and right tubes).

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Modular Chestpiece

Figure 3 illustrates a chestpiece 50 for use with a stethoscope such as the one illustrated in Figure 1. The chestpiece 50 comprises a trunk 56 which is connected to a stem 52 which is, in turn, connected to a main tube 54.

The trunk extends as a column, and has two sides, a bottom 58 and a top 60. (It is to be realised that the terms 'top' and 'bottom' are chosen arbitrarily in this context; in fact, in an embodiment, the trunk is rotatable on the stem and has two operable ends, each with a different function). The chestpiece further comprises a base 60 connected to the bottom 58 of the trunk 56.

D The base 60 comprises a frame piece 66 which is connected to the bottom 58 of the trunk 56. A retainer (also referred to as a "retaining ring") 62, which connects to a diaphragm 64 (illustrated as transparent in Figure 3), is further connected to the frame piece 66. In this embodiment, the retainer 62 is formed as an overmould over the diaphragm disc and is flexible.

A cover 68 attaches to the bottom 58 of the trunk 56, and covers the frame piece 66.

In the embodiment illustrated, the active connections of the parts of the base 60 are the connection between the trunk and the frame piece 66, between the frame piece 66 and the retainer 62, and between the cover 68 and the trunk 58. The o connections between the frame piece 66 and the retainer 62 is a friction fit assisted by the material of the retainer 62 which is a flexible polymer having a relatively high coefficient of friction.

The connections between the trunk 56 and the cover 68 as well as that between the frame piece 66 and the trunk 56 are snap-fit connections. In alternate ?5 embodiments threaded connections or other suitable connections may be used instead, or as well as, snap fit connections.

The cover 68 may be removed from the chestpiece 50 without affecting the other parts thereof. Furthermore, a snap-fit connection or a threaded connection may allow a user to remove and install a new cover, thereby potentially improving the ease with which the chestpiece 50 may be maintained. This, in turn, may provide for a chestpiece which is easier to maintain and service.

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As further illustrated in Figure 3, an annular void 70 is formed between the frame piece 66 and the cover 68. The annular void 70 may help to insulate the void between the cover 68 and the diaphragm 64. This may help to prevent sounds from outside the stethoscope from entering the channel amplifying and transmitting sound waves. This may provide a stethoscope which is more reliable and easier to use.

The cover 68 may be made from a different material to the trunk 58. The trunk 58 in this embodiment is made from stainless steel and the user is provided with options of material for the cover including plastic such as ABS; wood, metal etc. In a further embodiment, the cover 68 and the trunk 58 are made from the same o material.

Diaphragm Adjustment

Figure 5 illustrates a portion of a chestpiece 80. The ringed portion is shown in detail at the bottom of the Figure. The chestpiece 80 is similar to the chestpiece 50 illustrated in Figures 3 and 4. Illustrated in detail in Figure 5 is the retainer 82 which connects to the diaphragm 84 and keeps the diaphragm in place relative to the remaining structure of the chestpiece 80.

As illustrated, the retainer (also referred to as an adaptor) 82 has an anchor portion 90 for attachment to the structure of the chestpiece 80 (for example to the frame piece 66 of the chestpiece illustrated in Figure 3). The retainer 82 further D comprises a diaphragm attachment 86 to which the diaphragm 84 attaches.

The anchor portion 90 attaches to the diaphragm attachment 86 at an annular V-shaped groove 88 formed in the retainer 82. The groove 88 forms a region of weakness in the retainer 82.

During use, the diaphragm 84 is tuneable in that a user is able to vary the ?5 pressure with which the chestpiece 80 is brought into contact with a user's skin. This varying pressure changes the response characteristics of the diaphragm. The tauter the diaphragm, the more responsive it is to higher-frequency sound. By providing a region of weakness such as the groove 88, the extent to which the diaphragm is tuneable is potentially increased.

Multifrequency

Figure 6 is a schematic illustration of a chestpiece 100 according to a further

17991857_1 (GHMatters) P113762.AU.1 25/08/21 embodiment. The chestpiece 100 is similar to the chestpiece 50 illustrated in Figures 3 and 4. The chestpiece 100 includes a tuning mechanism comprising a plunger 102 which is engaged with the structure 104 of the chestpiece 100. The structure 104 includes the trunk, frame piece and other elements of the chestpiece as illustrated in Figures 3 and 4.

The interface between the plunger 102 and the structure 104 is a threaded interface 106. The plunger 102 is anchored against rotation relative to the structure 104 so that, as the structure 104 is turned, the plunger moves up and down relative to the structure 104 in the direction of the arrows 108.

D The structure 104 has diaphragm 110 attached thereto by a flexible retainer 112. The plunger 102 has an annular engaging surface 114 which is brought into engagement with the flexible retainer 112. As the annular engaging surface 114 engages with the flexible retainer 112 the flexible retainer 112 is deformed, thereby stretching the diaphragm.

Although not shown in the Figures, the threaded interface between the plunger 102 and the structure 104 includes an indexing system which provides the user with feedback once the structure 104 has been rotated a predetermined amount relative to the plunger, thereby raising or lowering the plunger by a predetermined amount. In this embodiment, there are three indexes provided, a first D with no engagement between the plunger and the flexible retainer, a second corresponding to an intermediate extension of the plunger relative to the flexible retainer, and engagement therewith; and a third corresponding to the maximum extension of the plunger relative to the flexible retainer, and engagement therewith.

In this embodiment, where three indices are provided, the user is able to ?5 select between three settings corresponding to low (no engagement); medium (intermediate engagement); and high (maximum engagement). Each setting corresponds to the frequencies of sound which the index relates to. So, for example, on the low setting, the stethoscope will be more responsive to low frequency noises.

The position of the plunger relative to the flexible retainer, and subsequent deformation of the plunger, when the dial is at the high setting is shown in Figure 7.

Since the tuning of the diaphragm is indexed, the behaviour of the diaphragm is more predictable, resulting in a potentially more accurate instrument.

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The user may turn the structure 104 relative to the plunger 102 to set the tuning and the structure then acts as a dial.

In this embodiment, the plunger 102 engages the flexible retainer 112, but in alternate embodiments, the plunger may engage the diaphragm 110 as well as, or instead of, the flexible retainer.

Figures 8 and 9 are schematic illustrations of a chestpiece 150 according to a further embodiment. The chestpiece 150 is similar to the chestpiece 50 illustrated in Figures 3 and 4 and the chestpiece 100 illustrated in Figures 6 and 7. The chestpiece 150 includes a structure 66 which comprises the trunk, frame piece and D other elements of the chestpiece as illustrated in Figures 3 and 4 and therefore forms part of the housing of the chestpiece 150.

The chestpiece 150 further comprises a diaphragm 184 attached to a flexible retainer162. The flexible retainer 162 is similar to the flexible retainer 112 of the chestpiece 100 but is attached to a circumferential frame 160. The frame 160 engages with the structure 66 of the chestpiece by means of a threaded engagement 170.

Figure 8 shows the chestpiece 150 when the membrane 184 is in a relaxed state. In this state, the frame 160 has been unscrewed relative to the structure 66. As the frame 160 is screwed onto the structure 66 (clockwise from the bottom of the D chestpiece 150), the frame 160 moves up relative to the structure 66. In this respect, the frame 160 acts as a dial. The structure 66 is formed with two annular projections 180 and 182 on the underside and as the frame moves up, the diaphragm 184 also moves up until the retainer 162 is in contact with the outermost projection 180, as shown in Figure 9. Contact between the projection 180 and the ?5 retainer 162 will cause the flexible retainer 162 to stretch and will thereby place the diaphragm under tension, thereby tuning the diaphragm in a manner analogous to that described above with reference to Figures 6 and 7. Similar to the embodiment of Figures 6 and 7, the chestpiece 150 of Figures 8 and 9 comprises an index system to allow a user to select predetermined tensions for the diaphragm with tactile feedback.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of

17991857_1 (GHMatters) P113762.AU.1 25/08/21 the common general knowledge in the art, in Australia or any other country.

In the claims which follow and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments. Similarly, the word "device" is used in a broad sense and is intended to cover the constituent parts provided as an integral whole as well as an instantiation where one or more of the constituent parts are provided separate to one another.

D

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Claims (37)

Claims

1. A stethoscope comprising a chestpiece connected to at least one eartip by at least one annular tube, the annular tube comprising a circumferential wall defining a central void wherein the central void extends along a length of the tube, the circumferential wall having one or more voids formed therein.

2. The stethoscope according to claim 1 wherein the annular tube is ring shaped with a substantially circular or oval cross-section. D

3. The stethoscope according to claim 1 or claim 2 wherein the central void extends along an entire length of the tube.

4. The stethoscope according to any preceding claim wherein the circumferential wall in which the one or more voids are formed is an outer circumferential wall.

5. The stethoscope according to any preceding claim wherein the voids formed in the circumferential wall extend through an entire circumference of the o tube.

6. The stethoscope according to any preceding claim wherein one or more voids in the circumferential wall extend along a length of the tube.

?5 7. The stethoscope according to any preceding claim wherein the voids in the circumferential wall define an outer wall and an inner wall, the stethoscope further comprising ribs joining the circumferential wall to the outer wall.

8. The stethoscope according to any preceding claim comprising more than one central void extending along a length of the tube.

9. A chestpiece for a stethoscope comprising a trunk for connection to a stem, the trunk having a bottom, and a base connected to the bottom of the trunk so that, in use, the base collects sound when in contact with a patient and the sound is transmitted via the trunk and the stem to a user, wherein the base comprises a retainer for retaining a diaphragm in place and a cover defining at least a portion of a visible surface of the chestpiece.

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10. The chestpiece according to claim 9 wherein the stem, retainer and cover are separate pieces which are connected together to form the chestpiece.

11. The chestpiece according to claim 10 wherein the trunk, retainer and cover are connected together by means of a snap-fit connection and/or a threaded interface.

12. The chestpiece according to any of claims 9 to 11 wherein the cover is o made from a different material to the trunk.

13. The chestpiece according to any of claims 9 to 12 wherein the cover is manually removable and may be interchanged by a user.

14. The chestpiece according to any of claims 9 to 13 wherein the retainer comprises an overmould to retain a diaphragm.

15. The chestpiece according to any of claims 9 to 14 further comprising a void formed in the base. D

16. The chestpiece according to any of claims 9 to 15 wherein the void formed in the base is an annular void between the retainer and the cover.

17. A chestpiece for a stethoscope comprising a housing and a flexible ?5 adaptor for engaging a diaphragm to the housing, wherein the flexible adaptor comprises a region of weakness proximate a point of engagement with the diaphragm.

18. The chestpiece according to claim 17 wherein the region of weakness allows flex of the diaphragm relative to the housing.

19. The chestpiece according to claim 17 or claim 18 wherein the region of weakness is annular.

20. The chestpiece according to any of claims 17 to 19 wherein the diagram is retained in the chestpiece by a flexible adaptor, the flexible adaptor having an attachment for engaging with the diaphragm, an anchor for engaging with

17991857_1 (GHMatters) P113762.AU.1 25/08/21 the chestpiece, and a flexible join joining the anchor and the attachment, wherein the flexible join is more flexible than the attachment and/or the anchor.

21. The chestpiece according to claim 20 wherein the retainer is formed as a single unit and is moulded.

22. The chestpiece according to claim 21 or claim 22 wherein the retainer is formed as an overmould.

D 23. The chestpiece according to any of claims 20 to 22 wherein the flexible join is formed by a portion having a smaller cross section than either the attachment or the anchor.

24. The chestpiece according to any of claims 20 to 23 wherein the flexible join is made from a material having a lower Young's modulus than the material forming the attachment and/or the anchor.

25. The chestpiece according to any of claims 20 to 24 wherein a movement of the flexible region is movement in a direction which stretches or D loosens the diaphragm during use of the chestpiece.

26. A chestpiece for a stethoscope comprising a housing and a connector for engaging a diaphragm to the housing wherein the connector comprises a tuning mechanism for altering a tension in the diaphragm by stretching and relaxing the ?5 diaphragm, wherein the connector further comprises a user control for setting the tuning mechanism to thereby allow the user to select a predetermined tension for the diaphragm.

27. The chestpiece according to claim 26 wherein the predetermined tension is fixed.

28. The chestpiece according to claim 26 or claim 27 wherein the user control is a dial.

29. The chestpiece according to claim 28 further comprising a base wherein the dial is located at a circumference of the base.

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30. The chestpiece according to claim 28 or claim 29 wherein the dial is indexed.

31. The chestpiece according to any of claims 28 to 30 wherein the tuning mechanism comprises a plunger attached to the dial so that rotation of the dial causes stretching of the diaphragm.

32. The chestpiece according to claim 31 wherein the tuning mechanism D further comprises a flexible retainer for retaining the diaphragm in position wherein the plunger causes flex of the flexible retainer.

33. The chestpiece according to any of claims 28 to 32 wherein rotation of the dial in a first direction causes raising of the plunger and rotation of the dial in an opposite direction causes lowering of the plunger.

34. The chestpiece according to any of claims 26 to 30 wherein the housing comprises a projection and wherein the tuning mechanism comprises a threaded portion between the housing and the connector so that rotation of the D connector relative to the housing moves the diaphragm or the connector into engagement with the projection, to thereby cause stretching of the diaphragm.

35. The chestpiece according to claim 34 wherein the connector comprises a dial.

36. The chestipiece according to claim 35 wherein movement of the connector relative to the housing is indexed.

37. The chestpiece according to any of claims 34 to 36 wherein the projection comprises an annular projection at a bottom of the housing.

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