GB2528119A

GB2528119A - Improvements in and relating to loudspeakers

Info

Publication number: GB2528119A
Application number: GB1412354.1A
Authority: GB
Inventors: Stuart Michael Nevill; Chen Jiang
Original assignee: B&W Group Ltd
Current assignee: Bowers and Wilkins Group Ltd
Priority date: 2014-07-11
Filing date: 2014-07-11
Publication date: 2016-01-13
Anticipated expiration: 2034-07-11
Also published as: GB201412354D0; GB2528119B

Abstract

The earpiece 2 includes a diaphragm 10 and a chassis 20. The earpiece 2 includes a first cavity 24 formed by a first surface of the diaphragm and a first surface of the chassis; a second cavity 26 formed by a second surface of the chassis; and a third cavity 28 formed by the first surface of the chassis and a second surface of the diaphragm 10. The first cavity 24 is connected with the second cavity 26 via a first set of holes 30 formed in the chassis 20. The third cavity 28 is connected with the second cavity 26 via a second set of holes 32 formed in the chassis 20 (and see figs 2a, b). Thus an acoustic resistance is provided between the first and second cavities 24, 26 and between the second and third cavities 26, 28 using the holes 30 of the first set and the holes 32 of the second set respectively.

Description

Tmprovements in and relating to loudspeakers

Technical Field

The present invention relates to improvements in and reiating to ioudspeakers. More particulariy, this invention concerns the improved damping of ioudspeakers, in particuiar loudspeakers for use in headphone earpieces. The invention also concerns an improved earpiece, headphones comprising such an earpiece, use of such an earpiece and a method of manufacturing such an earpiece.

Background of the Invention

A loudspeaker drive unit uypically includes a diaphragm 0) (also known as a cone), a chassis (also known as a basket or 0 frame), a voice coil and a drive magnet. The diaphragm is typically attached to the chassis via a flexible suspension of some sort. The voice coil is nypically attached to the diaphragm so that in use an electrical current is applied to the voice coil generating an electromagnetic field which interacts with the magnetic field of the driver magnet thereby causing the voice coil and consequently the diaphragm to move.

In headphone earpieces the drive unit is typically located within a housing. The drive unit is typically mounted on a baffle which connects the drive unit to the housing.

In order to maintain sound quality in use it is desirable to damp resonances (i.e undesirable vibration) of the earpiece, particularly when aiming to accurately reproduce low freguencies. When a headphone earpiece is placed adjacent to the ear a cavity is defined benween the ear, the baffle and the front of the diaphragm. One way in which resonances can be damped is by providing one or more holes (i.e. vents) in the baffle which defines the cavity in order to form an acoustic short circuit. The air in such holes may, at certain frequencies, act as an aooustic mass. The acoustio performance of such holes can be improved by covering the hole with a layer of damping material in order to increase the acoustic resistance provided by the hole.

An earpiece may also contain other cavities, for example a cavity formed between the diaphragm and the chassis that supports it. The acoustic properties of these other cavities may also be used to damp resonances in the earpiece. One way in which this can be done is by providing one or more vents in the structure (typically the chassis) defining this cavity.

Such vents may act to control die compliance of the cavity and thereby affect the resonance of the earpiece. Again, the acoustic performance of such vents may be improved by covering the vent with a layer of damping material in order to increase the acoustic resistance provided by the hole.

Providing vents in the cavity-defining structure and covering such vents with damping material as a solution increases the complexity of the structure of the earpiece, and may increase the number of components of the earpiece. This can result in additional cost during the manufacture stage.

The present invention seeks to mitigate one or more of the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved headphone earpiece. Alternatively or additionally, the present invention seeks to provide a headphone earpiece which can provide inproved acoustic performance. Alternatively or additionally, the present invention seeks to provide a headphone earpiece which can be more efficiently manufactured.

Summary of the Invention

According to a first aspeot of the invention there is provided a headphone earpieoe inoiuding a loudspeaker diaphragm and a chassis, wherein the earpiece includes a first oavity formed at least in part by a first surface of the diaphragm and a first surface of the chassis; a second cavity formed at least in part by a second surface of the chassis, the second surface of the chassis being on the opposite side of the chassis to the first surface; a third cavity formed at least in part by the first surface of the chassis and a second surface of the diaphragm, the second surface of the diaphragm being on the opposite side of uhe diaphragm to the first surface; and wherein the first cavity is connected with the second cavity via a first set of holes formed in the chassis and the third cavity is connecued with the second cavity via a second set of boles formed in die chassis, such that an 0 acoustic resistance may be provided between the first and second cavities and between the second and third cavities using the holes of the first set and the holes of the second set respectively. Thus, with the present invention it may be possible to reduce unwanted modes of vibration in the earpiece using holes in one and the same component, the chassis.

It will be understood thau the chassis of the present invention may be of a monolithic, which is to say a single piece, construction. Providing the first and second set of holes within the same componenc simplifies the design of the earpiece and may therefore improve the efficiency of the manufacturing process. Having fewer components also results in fewer boundaries between components. Boundaries may impact on acoustic performance by refleccing sound and must therefore be considered during the design process. Thus, reducing the number of components may simplify the design process.

The holes of the first sec may form an acoustic short circuit. The amount of acoustic resistance provided using the holes of the first set may affect the properties of the acoustic short circuit formed by the first holes. Thus, it may be possible to reduce unwanted vibration in the earpiece by tuning the properties of the acoustic short circuit using an acoustic resistance provided via the holes of the first set. The amount of acoustic resistance provided using the holes of the second set may affect the effective compliance of the third cavity. The compliance cf the third cavity will interact with the flexible support of the drive unit to affect the stiffness of the diaphragm/support system and therefore the resonance of the earpiece. Thus, it may be possible to reduce unwanted vibration in the earpiece by altering the compliance of the third cavity using an acoustic resistance provided via the holes of the second set. The present o invention allows both of these mechanisms for affecting the acoustic performance of an earpiece, particularly at low frequencies, to be implemented using a single component (the chassis) The chassis may be arranged and configured so as to be suitable for supporting a loudspeaker diaphragm. The diaphragm may comprise a cone shaped member. The outer edge of the diaphragm may be circular.

In certain embodiments the holes of the first and/or second set are passageways from one side of the chassis to the other, preferably but not necessarily passageways which in cross-section through the plane of the chassis are closed. In certain enbodiments the holes of the first set may be located at the edge of the chassis such that the hole is not entirely circumscribed by the chassis.

In certain embodiments, the connection between the cavities via the holes is such that air can move from one side of the chassis to the other. For example, the holes of the first set may provide an acousuic short circuit between the first and second cavities. The cavities may be in fluid communication via the holes. Thus, the first cavity may be in fluid comnunication with the second cavity via the holes of the first set. The third caviny may he in fluid communication with the second cavity via the holes of the second set. For example, the compliance of the third cavity may depend on the acoustic resistance provided via the holes of the second set.

The cavities may be acoustically coupled via the holes. Thus, the first cavity may be acoustically coupled with the second cavity via the holes of the first set. The third cavity may be acoustically coupled with the second cavity via the holes of the second set.

___ 15 It will be understood thaiii the term cavity may refer to an open-sided cavity. That is to say the cavity may not be 0 entirely circumscribed by structure. For example, the cavity may be defined by structure on five sides while being open on a sixth side (in the six direcuions defined by three orthogonal axes) . In use, a cavity may be circumscribed on the sixth side by the ear of a user. A cavity may be defined by other structural elements in addition to those discussed above.

The headphone earpiece may include a housing. The housing may include at least one side wall. The housing may have an open end. In use, the open end of the housing may be positioned adjacent to the ear of the user. The housing may have a closed end. The inside surface of the closed end of the housing may be referred to as The base of the housing. The diaphragm may be located within the housing. The chassis may be located within the housing.

The headphone earpiece may be suitable for use in headphones, for example circumaural, supra-aural or intra-aural headphones. The headphone earpiece may be arranged and configured to encompass the ear. The headphone earpiece may be arranged and configured to press against the ear. The headphone earpiece may be suitable for fitting in the outer ear (i.e. an earbud) or inserting in the ear canal (i.e. an in-ear earpiece) The first surface of the diaphragm may be defined as the surface of the diaphragm on the far side of the diaphragm to the base (i.e. inner surface of the closed end) of the housing. The second surface of the diaphragm may be defined as the surface of the diaphragm on the near side of the diaphragm to the base of the housing. The first surface of the chassis may be defined as die surface of the chassis on the far side of the chassis to the base of the housing. The second surface of the chassis may be defined as the surface of the chassis on the near side of the chassis to the base of the C housing. The first and second surface may be similarly defined for other components. It will be understood that where a component is non-planar, the first surface may comprise all those surfaces of the ccmponenu located on the far side of the component to the base of the housing. Similarly, the second surface may comprise all those surfaces of the component located on the near side of the component to the base of the housing.

It may be that the first and third cavities are separate from each other. That is to say, there may be no significant fluid flow between the first and third cavities. It may be that the first and third cavities are separated by the diaphragm. Tt may be that the first and third cavities are separated by the diaphragm and the surrounding support.

The acoustic resistance between the first and second cavities nay be provided, at least in part, by damping material which covers each hole of the first set. The acoustic resistance between the second and third cavities may be provided, at least in part, by damping material which covers each hcie of the second set. Each hole of the first set may be covered by damping material. Each hole of the second set may be covered by damping material. Thus, the acoustic resistance of each hole of the first and/or second set will depend cn the properties of the damping material coving the hole. A layer of damping material may be arranged and configured to cover the holes of the first and second set.

The layer of damping material may be on the same side of the chassis as the second surface. A layer of damping material may be arranged and configured to cover the second surface of the chassis. The layer of damping material may be directly adjacent to the second surface of the chassis. The layer of damping material may abut the second surface of the chassis over the majority of the surface area of the second surface.

The layer of damping material may be attached to the second surface of the chassis. For example, the layer of damping material may be attached to the second surface of the chassis using an adhesive. The damping material may be a mesh, for example a woven or non-woven material. The damping material may be a porous paper material. The damping material may be a porous foam, for example an open-cell foam. It will be appreciated that a damping material may be selected such that the properties of the damping material allow air to pass through a hole when covered by the damping material. The properties of the damping material coving a hole may affect the rate at which air moves beuween the cavities. Thus, by choosing an appropriate damping material the acoustic resistance provided via each hole may be tuned. Thus, the damping material may be used to improve the acoustic performance of the earpiece.

The layer of damping material may contain one, two, or more than two types of damping material. For example, a first type of damping material may be arranged and configured to cover the holes of the first set. A second type of damping material nay be arranged and configured to cover the holes of the second set. Having different types of damping material for each set of holes may improve the acoustic performance of the earpiece by allowing a suitable material to be used to damp each cavity.

A single piece of damping material may cover the second surface of the chassis. A single piece of damping material may cover the holes of the first set and the holes of the second set. Thus, one and the same piece of material may be used to provide an acoustic resistance between both the first and second cavities and the second and third cavities. Using a single piece of damping material reduces the number of 0 components in the earpiece and may therefore improve the efficiency with which the earpiece can be manufactured. A single piece of damping material may extend across all the holes of the first set and all the holes of the second set.

It may be that different regions of the single piece of material have different damping properties. This may allow the holes of the first and second sets to be damped differently, thereby improving the acoustic performance of the earpiece.

The chassis may include a recess. The recess may be arranged and configuration to accommodate the diaphragm.

The recess may be formed in or by the shape of the first surface of the chassis. The recess may include a flat bottom surface. The recess may include at least one side wall. The chassis may include a substantially planar portion. The planar portion may circumscribe the recess. The planar portion may extend outwardly from the edge of the recess. The edge of the recess may round. For example, the edge of the recess may be generally circular. The edge of the recess may be circular. Thus, the recess may appear generally circular when viewed in plan. The cuter edge of the planar portion of the recess may have four discernable sides, for example two pairs of sides arranged opposite each other. The sides may be curved. The outer edge of the planar portion may have discernable corner portions benween each side. The outer edge of the planar portion of the chassis may be substantially rectangular, for example a generally sguare shape. Thus, the outer edge of the planar portion may appear rectangular when viewed in plan. The outer edge of the planar portion may be the outer edge of the chassis. Thus, the chassis may be rectangular when viewed in plan. The recess may be located in the centre of the chassis. The radius of the recess may be only slightly less than half the width of the chassis. For example, the radius of the recess may be between 0.5 mm and o 2.5 mm less than half the width of the square.

The diaphragm may be locaced in the recess. Thus, the chassis may include a recess in which the diaphragm is located and a substantially planar porcion extending from the edge of the recess. The first cavity may be formed at least in part by the first surface of the planar portion of the chassis and the first surface of the diaphragm. The third cavity may be formed at least in part by the first surface of the portion of the chassis that forms the recess and the second surface of the diaphragm.

The holes of the first sec may be located in a different region of the chassis to the boles of the second set. The holes of the first set may be located at a greater radial distance from the centre of the chassis than the holes of the second set. The holes of the first set may be formed in the planar portion of the chassis. All of the holes of the first set may be formed in the planar portion of the chassis. When -10 -the outer edge of the planar portion is reotangular, for example square, the holes of the first set may be located in the region of the corners of the rectangle. The holes of the first set may be grouped in pairs.

The holes of the second set may be formed in the recessed region of the chassis. All of the holes of the second set may be formed in the recessed region of the chassis. The holes of the second set may be formed in the bottom surface of the recess.

The edge of each hole of die first and/or second set may be located at least 0.3 mm, for example 0.5 mm from the edge of another hole of the first and/or second set.

There may be more boles in the second set than in the first set. For example, there may be more than two, three or more than three, times the number of holes in the second set as compared to the first set. For example, there may be four or more holes, possibly up to cen holes, for example eight holes, in the first set and more than fifteen holes, more than twenty holes, for example twency two holes, in the second set.

A hole of the first or second set may have substantially the same cross-sectional shape as all the other holes of that set. The holes of the first set may have a different cross-sectional shape to the holes of the second set. The holes of the second set may have a generally circular cross-sectional shape. The holes of the first set may have a generally triangular cross-sectional shape.

A hole of the first or second set may occupy a portion of the surface area of the chassis. The portion of the surface area of the chassis occupied by a hole may be equal to the cross-sectional area of that hole. The cross-sectional area of a hole may vary by +/-10% Throughout its depth. The cross-sectional area of a hole may be substantially constant throughout its depth. A hole of the first or second set may

-II -

have a cross-sectional area that differs from the cross-sectional area, at the same depth, of each of the other holes of that set by no more than 10%. A hole of the first or second set may have substantially the same cross-sectional area as all the other holes of that sec. The holes of the first set may have a different cross-seccional area to the holes of the second set. The cross-sectional area of a hole of the first set may be greater than the cross sectional area of a hole of the second set. For example the cross-sectional area of a hole of the first set may be more than two, three or more than three, tines the cross-sectional area of a hole of the second set. Each hole of the first set may have a cross-sectional area of between 0.1 mm2 and 32 mm2, for example between 10 mm2 and 32 mm2. Each hole of the second set may have a cross-sectional area of between 0.2 mm2 and 7 mm2. The holes of the 0) first set may occupy the majority of the surface area of the o planar portion. The holes of die second set may occupy less than half of the surface area of the recessed portion of the chassis. The holes of the second set may occupy less than half of the surface area of the bottom surface of the recess.

The holes of the second set may occupy more than 5% of the surface area of the bottom surface of the recess.

The dimensions of the recess may be such that the recess occupies more than half of the surface area of the chassis.

For example, the recess may occupy 80% of the surface area of the chassis.

The earpieoe may include a baffle. The chassis may be connected to the housing via the baffle. The baffle may be substantially planar. The baffle may extend across the housing between the side walls. The baffle may include am opening.

The chassis may be located in che opening such that the first surface of the chassis is level with the first surface of the baffle. The first surface of die baffle may partly define the -12 -first cavity. A second surface of the baffle may partly define the second cavity, the second surface of the baffle being on the opposite side of ihe baffie to the first surface.

The first surface of the baffie may be defined as the surface of the baffle on the far side of the baffle to the base of the housing. The second surface of the baffie may be defined as the surface of the baffie on the near side of the baffle to the base of the housing.

The earpiece may include a cushion. The cushion may extend around the majority of die edge of the open end of the housing. In use, the cushion may be located adjacent to the ear of the user. The cushion may also define, at least in part, the first cavity.

The loudspeaker diaphragm and chassis of the earpiece may form part of a moving-coil type loudspeaker. The earpiece may include a voice coil attached co the throat of the cone shaped 0 diaphragm. The drive unit may include a generally annular magnet. The magnet may include an annular groove. The voice coil of the diaphragm may be located in the annular groove of the magnet. The magnet may be located in the recess of the chassis. The magnet may be located on the same side of the chassis as the diaphragm.

The earpiece may include a support that connects the outer edge of the diaphragm to the chassis. The support may be annular. The support may have a u-shaped cross-section.

The support may be made of flexible and/or resilient material.

The first surface of the support may also define, at least in part, the first cavity. The second surface of the support may also define, at least in part, the third cavity, the second surface of the support being on the opposite side of the support to the first surface. The first surface of the support may be defined as the surface of the support on the far side of the support to the base of the housing. The -13 -second surface of the support may be defined as the surface of the support on the near side of the support to the housing.

The earpiece may include further suspension eiements in addition to the support.

According to a second aspect of the invention, there is provided a chassis for use in an earpiece in accordance with the first aspect opticnaiiy incorporating any of the various features described or claimed herein with reference to the first aspect.

According to a third aspect of the invention, there is provide a set of headphones including an earpiece in accordance with the first aspect optionally incorporating any of the various features described or claimed herein with reference to the first aspect. The set of headphones may include two earpieces in accordance with the first aspect.

According to a fourth aspect of the invention there is C provided a headphone earpiece for wearing adjacent to the ear of a user including a loudspeaker diaphragm and a chassis, wherein, in use, the earpiece comprises a first cavity formed at least in part by a first surface of the diaphragm, a first surface of the chassis and the ear of the user; a second cavity formed at least in part by a second surface of the chassis, the second surface of the chassis being on the opposite side of the chassis to the first surface; a third cavity formed at least in part by the first surface of the chassis and a second surface of the diaphragm, the second surface of the diaphragm being on the opposite side of the diaphragm to the first surface; and wherein the first cavity is connected with the second cavity via a first set of holes formed in the chassis and the chird cavity is connected with the second cavity via a second set of holes formed in the chassis, such that both the first and third cavities are acoustically damped by means of the holes in the chassis.

-14 -According to a fifth aspect of the invention, there is provided a method of damping vibration in a headphone earpiece having a ioudspeaker diaphragm, the method including the steps of: providing a chassis including a plurality of holes and arranging the chassis and diaphragm within the earpiece such that a first cavity is formed at least in part by a first surface of the diaphragm and a first surface of the chassis; a second cavity is formed at least in part by a second surface of the chassis, the second surface of the chassis being on the opposite side of the chassis to the first surface; a third cavity is formed at least in part by the first surface of the chassis and a second surface of the diaphragm, the second surface of the diaphragm being on the opposite side of the diaphragm to the first surface; and the first cavity is connected with the second caviuy via a first set of holes formed in the chassis and the Third cavity is connected with the second cavity via a second set of holes formed in the chassis, such that an acoustic resistance may be provided between the first and second cavities and between the second and third cavities using the boles of the first set and the holes of the second set respeccively.

The method may further include a step of providing a layer of damping material on the second surface of the chassis. The step of providing a layer of damping material may include providing a single piece of damping material arranged and configured to cover the holes of the first set and the holes of the second sec.

Any features described wich reference to one aspect of the invention are equally applicable to any other aspect of the invention, and vice versa.

-15 -

Description of the Drawings

Various embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings of which: FIG. 1 shows a schematic sectional view of a headphone earpiece in accordance with a first embodiment of the present invention.

FIG. 2 shows (a) front and (b) back schematic views respectively of part of a chassis assembly in accordance with the first embodiment.

FIG. 3 shows a flow diagram for a method of damping vibration in a headphone earpieoe in accordance with a second embodiment of the present invention. a)

o Detailed Description

FIG. 1 shows a schematic sectional view of a headphone earpiece in accordance with the first embodiment of the present invention. The earpiece 2 includes a housing 4, having a base 4a and side walls 4b, within which components of the loudspeaker driver system 6 of the earpiece are located.

A cushion 8 extends along the end of the side walls 4b distal to the base of the housing 4a. The driver 6 includes a cone-shaped diaphragm 10 located concentrically within the housing 4. A voice coil 12 attached to the throat of the diaphragm 10 extends into an annular groove 14 formed in a magnet 16. A planar baffle 18 is located wiuhin the housing 4 and extends inwards from the sidewalls 4a in the same plane as the outermost edge of the diaphragm 10. A chassis 20 extends across the housing 4 between the innermost edges of the baffle 18, separating the diaphragm 10 and magnet 16 on the one side from the base of the housing 4b on the other side. The -16 -outermost edge of the diaphragm 10 is connected to the chassis via an annular support 22 in the form of a resilient suspension ring which appears u-shaped when viewed in cross-section in FIG. 1. A pianar portion 20a of the chassis 20 extends from the innermost edge of the baffle 18 to the edge of the support 22. The chassis 20 includes a central recessed region 2Gb. The cone-shaped diaphragm 10, support 22 and magnet 16 sit within the recess. The thickness of the chassis has been exaggerated in FIG. 1 to aid the discussion of the present invention. A first cavity 24 is defined on the side of the diaphragm furthest from the base of the cavity 4b by the surface of the planar portion of the chassis 20a, the surface of the support 22, and the surface of the diaphragm 10. A second cavity 26 is formed between the opposite surface (i.e. the surface nearest the base of the housing 4b) of the chassis 20 (including the planar portion 20a and the recessed o region 2Gb) and the housing 4b. A third cavity 28 is formed within the recess between the diaphragm 10, support 22 and the surface of the recessed region of the chassis 20b. The planar portion of the chassis 20a includes a plurality of holes 30 in the region of the chassis which separates (and is therefore disposed between) the first and second cavities 24, 26. The recessed region 2Db of the chassis 20 includes a plurality of holes 32 in the region of the chassis which separates (and is therefore disposed between) the second and third cavities 26, 28. A dust cover 34 extends across the housing at the level of the cushion 8. A single piece of damping material 36, in the form of a layer of porous paper extends across the surface of the chassis 20 which is closest to the base of the housing 4b. The piece of damping material 36 covers the holes 30, 32.

In use the holes 30 connect the first cavity 24 to the second cavity 26 act as an acoustic short circuit, and are tuned by the properties of the damping material 36 thereby -17 -helping to damp resonance within the first cavity. The holes 32 connect the third cavity 28 to the second cavity 26 and thereby reduce the compliance of the third cavity, altering the resonance of the earpiece. The degree to which the compliance of the third cavity is reduced is determined by the prcpert±es of the damp±ng material 36. As such, a headphone earpiece in accordance with the present invention provides an improved acoustic performance using holes formed in one and the same component. Earpieces of the present invention also use one and the same piece of damping material to provide an acoustic resistance between both the first and second, and second and third cavities. Thus, a headphone earpiece in accordance with the present invention provides improved acoustic performance while reducing the number of additional components required. Reducing the number of components in the 0) earpiece may increase ease of manufacture. Reducing the 0 number of components in the earpiece also reduces the number of boundaries between the components; this may improve acoustic performance by reducing reflection from those boundaries and/or simplify the design process by removing the need to consider as many boundaries/components while designing the earpiece.

FIG. 2a and 2b are front and back views respectively of a portion of a chassis assembly in accordance with the first embodiment. FTG. 2a shows a front view of the chassis 20 which appears square when viewed in plan. The planar portion 20a of the chassis 20 extends from the outer edge of the chassis to the edge of the concentrically-located recess (not shown) in which the diaphragm 10, which appears circular when viewed in plan, is located. The annular support 22 extends between the edge of the planar portion of the chassis 20a and the outer edge of the diaphragm 10. The radius of the diaphragm 10 is only slightly less than half the width of the -18 -square such that the planar region of the chassis 20a is very narrow at the point where the support 22 is closest to the edge of the chassis 20 (i.e. midway along the sides of the square of the chassis 20) . A pair of holes 30, which connect the first cavity 24 to the second cavity 26, is located in each corner of the square chassis 20. Each hole 30 appears triangular when viewed in pian in FIG. 2a.

FIG. 2b shows a rear view of the chassis 20 of FIG. 2a.

The outer edge of the rear of uhe chassis 20 appears square when viewed in pian. The rear surface of the recessed portion of the chassis 20b appears circular when viewed in plan. The triangular holes 30 can be seen in each corner of the square chassis 20 and appear trianguiar when viewed in plan. The holes 32 which connect the third cavity 28 to the second cavity 26, can be seen in the recessed region of the chassis 20b, and appear circular when viewed in plan. Ihe damping o material 36, the extent of which is denoted by dashed line 38', extends across the back surface of the chassis 20.

FIG. 3 shows a flow diagram for a method of damping vibration in a headphone earpiece according to a second embodiment. The method includes providing 100 a chassis including a plurality of holes, providing 102 a single piece of damping material on the second surface of the chassis, and arranging 104 the chassis and a diaphragm within the earpiece in order to provide an earpiece having first, second and third cavities as described above. Thus, methods in accordance with the present invention allow an acoustic resistance to be provided between both the firsu and second cavities and the second and third cavities using a single piece of damping material. Reducing the number of component parts of the earpiece nay improve the ease of manufacture of the earpiece thereby reducing manufacturing cost and complexity.

-19 -Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifioally illustrated herein.

For example, while the chassis described above is rectangular and includes a circular recess, it may be that the outer chassis is generally square, that the edges of the chassis are curved and/or that the recess is non-circular.

The shape, number and arrangement of the holes of the first and second set may also differ from those illustrated in the particular embodiments described above.

Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable eguivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the 0 claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims.

Claims

-20 -Claims 1. A headphone earpiece including a loudspeaker diaphragm and a chassis, wherein the earpiece includes a first cavity formed at least in part by a first surface of the diaphragm and a first surface of the chassis; a second cavity formed at least in part by a second surface of the chassis, the second surface of the chassis being on the opposite side of the chassis to the first surface; a third cavity formed at least in part by the first surface of the chassis and a second surfaoe of the diaphragm, the second surface of the diaphragm being on the opposite side of the diaphragm to the first surface; and 0 wherein the first cavity is connected with the second cavity via a first set of holes formed in the chassis and the third cavity is connected with the second cavity via a second set of holes formed in the chassis, such that an acoustic resistance may be provided between the first and second cavities and between the second and third cavities using the holes of the first set and the holes of the second set respectively.
2. An earpiece according to claim 1, wherein a layer of damping material covers the holes of the first set and the holes of the second set.
3. An earpiece according to claim 2, wherein a single sheet of damping material covers the holes of the first set and the holes of the second set.
4. An earpiece according to claim 3, wherein the sheet of damping material is attached to the second surface of the chassis.

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5. An earpiece according to any preceding claim, wherein the chassis includes a recess In which the diaphragm is lccated and a substantially planar portion extending from the edge of the recess.
6. An earplece according to claim 5, wherein the holes of the first set are located In the substantially planar portlcn.
7. An earpiece according to claim 5 cr claim 6, wherein the holes of the second set are located in the recessed portion of the chassis.
8. An earpiece according to any of claims 5 to 7 wherein the outer edge of the planar portion of the chassis Is substantially rectangular and the outer edge of the recess is substantially circular.
9. An earplece according to any of claims 5 to 8, whereIn the holes of the first set occupy the majority of the surface area of the planar portion of the chassis.
10. An earpiece according to any of claims 5 to 9, wherein the holes of the second set occupy less than half of the surface area of the recessed portion of the chassis.
U. An earpiece according to any preceding claim, wherein the holes of the first set are located at a greater radial distance from the centre of the chassis the holes of the second set.
12. An earpiece according to any preceding claim, wherein the cross sectional area of each hole of the second set is less than the cross-sectional area of each hole of the first set.
13. A chassis for use as the chassis of the earpiece of any of claims 1 to 12.
14. A set of headphones IncludIng an earplece In accordance with any of claims 1 to 12.

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15. P. headphone earpiece for wearing adjacent to the ear of a user including a loudspeaker diaphragm and a chassis, wherein, in use, the earpiece comprises a first cavity formed at ieast in part by a first surface of the diaphragm, a first surface of the chassis and the ear of the user; a second cavity formed at ieast in part by a second surface of the chassis, the second surface of the chassis being on the opposite side of the chassis to the first surface; a third cavity formed at ieast in part by the first surface of the chassis and a second surface of the diaphragm, the seoond surface of the diaphragm being on LU the opposite side of the diaphragm to the first surface; and wherein the first cavity is connected with the 0 second cavity via a first set of hoies formed in the chassis and the third cavity is connected with the second cavity via a second set of holes formed in the chassis, such that an acoustic resistance may be provided between the first and second cavities and between the second and third cavities using the holes of the first set and the holes of the second set respectively.
16. P. method of damping vibration in a headphone earpiece having a loudspeaker diaphragm, the method including the steps of: i. providing a chassis including a plurality of holes, ii. arranging the chassis and diaphragm within the earpiece such that -23 -a first cavity is formed at least in part by a first surface of the diaphragm and a first surface of the chassis; a second cavity is formed at least in part by a seoond surfaoe of the chassis, the second surface of the chassis being on the opposite side of the chassis to the first surface; a third cavity is formed at least in part by the first surface of the chassis and a second surface of the diaphragm, the second surface of the diaphragm being on the opposite side of the diaphragm to the first surface; and the first cavity is connected with the second cavity via a first set of holes formed in the chassis and the third cavity is connected with the second cavity via a second set of holes formed in the chassis, such that an 0 acoustic resistance may be provided between the first and second cavities and between the second and third cavities using the holes of the first set and the holes of the second set respectively.
17. A method according to claim 16, wherein the method further includes the step of providing a layer of damping material on the second surface of the chassis.