This invention relates to an earphone that is placed by a user in their ear to hear sound.

An earplug is a device that is meant to be inserted in the ear canal to protect the user's ears from loud noises or the intrusion of water, foreign bodies, dust or excessive wind. It has been known for many years that there is a problem with the noise reduction capability of existing earplugs and ear defenders, as they cannot reduce sound well enough to comply with current health and safety laws on noise exposure. The safe limit of sound is just 85 dB for prolonged exposure, and the acceptable time period decreases greatly as the sound level increases.

An aim of the invention is to provide an earphone that has some of the characteristics of an earplug, and cuts out background noise from the environment while enabling the user to hear desired sounds. This may have applications either for pleasure or for work. It may enable a user for example to listen to music for pleasure without hearing loud background noise from the environment; or when working, to receive instructions transmitted by a wireless transmission technique such as Bluetooth, without hearing loud noise from the surroundings.

According to the present invention there is provided an earphone to fit into a user's ear canal comprising: a solid core of rigid material; a compressible and resilient tubular suspension layer, surrounding part of the core, for suspending and cushioning the core in a user's ear; and an electronic driver mounted on the core to couple sound into the core.

The combination of the solid core and the tubular suspension layer is effective at cutting out noise from the surroundings. The tubular suspension layer supports the core so that it can be located at least partly within the user's ear canal, the suspension layer separating the core from the surface of the ear canal. The electronic driver may be mounted on the core outside the ear canal. It will be appreciated that there is no hole or aperture through the core, and so no sound channel between the electronic driver and the other end of the earphone, which is the end that is in the user's ear canal in use; the sound transmission is therefore through the solid material of the core itself. The core of the device may be made of metal, such as stainless steel, mild steel, brass, titanium, aluminium or magnesium, or of a ceramic material such as alumina, tungsten carbide or titanium carbide. The suspension layer is made of one or more of foam, memory foam, rubber or silicone. A preferred material is memory foam, for example a viscoelastic polyurethane foam.

It will be appreciated that the materials of the core and of the suspension layer differ as regards their characteristic impedance, which is the product of density and the speed of sound, the speed of sound depending on the modulus of elasticity of the material and its density. By ensuring the material of the core and the material of the suspension layer differ very significantly in both density and modulus of elasticity, and therefore in their characteristic impedances, sound transmission from one material to the other is inhibited.

The core may be substantially cylindrical, or may comprise a first portion whose surface is a surface of revolution about a longitudinal axis, and a second substantially cylindrical portion extending coaxially from an end of the first portion, that end of the first portion being of larger diameter than the second portion, and the second portion is surrounded by the tubular suspension layer. In this case the first portion may be visible to the user, and the earphone would be inserted into the user's ear canal such that the suspension layer and the second portion are within the ear canal. The second substantially cylindrical portion may define one or more grooves, which may have angular edges; such grooves may enhance grip of the suspension layer to the second portion. The first portion may be substantially cylindrical, or may have narrow sections as well as wide sections.

In use, part of the earphone may therefore project outside the open end of the ear canal, and those parts of the earphone that are not intended to be inserted within the ear canal do not have to be surrounded by the suspension layer. They may therefore be decorative, for example being coated with an attractive metal such as gold or silver, or may be provided with a coloured finish by enamelling or (in the case of titanium for example) by anodising. The electronic driver is mounted on the core at or near the end that is remote from the user's eardrum in use, so sound from the driver is propagated through the core, and then transmitted into the ear canal. The driver may be bonded permanently to the core, for example by welding or gluing; or it may be held onto the core in a removable fashion, for example by a magnet (if the end of the core is of a ferromagnetic material), or by means of a resilient sleeve.

In each such earphone it is preferable if any corner of the core that may be expected to come into proximity with the skin of the user's ear or ear canal is rounded, to reduce the risk of the earphone scratching or abrading the skin. As regards those parts of the earphone that are expected to come into contact with the skin of the user's ear or ear canal, preferably there is at least 2 mm thickness of the tubular suspension layer between the outer surface of the earphone and any portion of the core, more preferably at least 3 mm, when the tubular suspension layer is in its initial un-squeezed state; and preferably there is at least 0.5 mm thickness of the tubular suspension layer when the earphone is in situ within the ear, for example 1 mm or 1.5 mm. When the earphone is in situ, for example within an ear canal, along at least one path around the periphery of the earphone the resilient material of the tubular suspension layer is squeezed to less than its initial state, which ensures a seal between the earphone and the inner surface of the ear canal along that peripheral path.

The invention will now be further and more particularly described, by way of example only, and with reference to the accompanying drawings, in which:

Figure la shows a side view of an earphone;

Figure lb is a longitudinal sectional view of the earphone of figure la;

Figure 2 shows a longitudinal sectional view of an alternative earphone;

Figure 3 shows a longitudinal sectional view of another alternative earphone;

Figure 4 shows a longitudinal sectional view of another alternative earphone; and Figures 5a, 5b and 5c show side views, partly in section, of modifications to the earphone of figure 4.

Figures 1(a) and 1(b) show an earphone 10, with a solid core 20, and a tubular suspension cap 40. In this embodiment the core is 17.5 mm in length, but more generally it may be between 10 mm and 25 mm long; in this embodiment the diameter of the largest portion of the core 20 is 8.5 mm, but more generally this diameter may be between 5 mm and 10 mm; it must be small enough to fit into the ear canal. The core 20 includes a first cylindrical portion 21 that will protrude out of the ear canal when the earphone 10 is inserted into the ear canal, and is the portion of largest diameter of the core 20. The length of the first portion 21 is 10 mm in this case, but it more generally may be between 7 mm and 14 mm. The first portion 21 has a flat end face 23, orthogonal to its longitudinal axis.

Preferably, the solid core 20 is made of a non-compressible rigid and dense material, for example a metal such as steel, titanium, aluminium or magnesium, or any other suitable metal, or from a ceramic material, or any other rigid material of suitable density. The tubular suspension cap 40 is made of a compressible material such as foam, memory foam, silicone or rubber; such a material has a significantly lower density and a much lower modulus of elasticity than the material of the solid core 20. In some cases the suspension cap 40 may be custom-moulded to an individual user's ears, and may be made from silicone or acrylic. The provision of the solid non-compressible inner core 20 inside the tubular suspension cap 40 significantly enhances the ability of the earphone 10 to cut out ambient noise.

An acoustic driver 25 is secured onto the flat end face 23 of the core 20 by a plastic sleeve 26. The internal details of the acoustic driver 25 are not shown, but the acoustic driver 25 generates sound waves at the end face 23 of the core, so that those sound waves are transmitted through the core 20. Signals may be provided to the acoustic driver by wires 24 (indicated schematically), or by a wireless

communication technique such as Bluetooth.

Inside the tubular suspension cap 40, the core 20 defines a second portion 22 of smaller diameter that that extends into the cap 40. The diameter of the second portion 22 in this embodiment is 4 mm, but may be between 3 and 6 mm for example. The second portion 22 is provided with two circumferential grooves 30, so as to define a ridge 28 between the grooves 30 and an end ridge 28a between one of the grooves 30 and the end of the second portion 22. In this embodiment the grooves 30 are approximately 0.5 mm deep. The grooves 30 are not rounded, so they have angular edges.

As shown, the core 20 defines two grooves 30 on the second portion 22, but there may be a different number of grooves 30, or indeed no grooves 30. Where there are multiple grooves 30, these grooves 30 may all be the same width and depth, but in some embodiments a device may be provided with ridges 28 of different sizes (diameter and/or length), for example they may get smaller or larger the further away they are from the first portion 21 of the inner core 20, or they may be unevenly spaced along the second portion 22 of the inner core 20. The more ridges 28 that are provided on the core 20, the greater will be the sound attenuation for ambient noise, so a particular material can be selected for the core 20 according to the use or application of the earphone 10 as well as the overall price.

In this example the tubular suspension layer 40 extends beyond the exposed end 32 of the solid core 20, and has a rounded shape so as to be comfortable when inserted into the ear. The tubular suspension cap 40 is sized to be a snug fit to the core 20, and the cap 40 has a square end that fits up against the base of the first portion 21 of the core 20. The second portion 22 of the core 20 is therefore contained within the cap 40, and so only the end 32 of the second portion 22 is exposed. The tubular suspension cap 40 is the portion of the earphone 10 that will be inserted into a user's ear. Hence in use the sound waves generated by the driver 25 propagate through the core 20 and are transmitted into the ear canal from the end 32.

The tubular suspension cap 40 may for example be entirely of a material such as memory foam. Alternatively, as indicated by broken lines in figure lb, the suspension cap 40 may consist of an inner tubular sleeve 41 of elastic material embedded within a material such as a memory foam, the tubular sleeve 41 being for example of a silicone elastomer and being a tight fit around the second portion 22 of the inner core 20, in this example the tubular sleeve 41 deforming into the grooves 30. The tubular sleeve 41 and its deformation into the grooves 30 ensure that the suspension cap 40 is securely attached to the core 20 during insertion and removal, and in use the suspension cap 40 supports and locates the core 20 so the second portion 22 is within the ear canal. As with known ear plugs that include a memory foam, in its initial, unsqueezed state the external diameter of the tubular suspension cap 40 is larger than that of the ear canal, but the suspension cap 40 can be squeezed or rolled between the user's fingers before being inserted into the ear canal, so that it goes in without difficulty; the memory foam then gradually expands to seal against the adjacent walls of the ear canal. The external diameter of the first portion 21 is less than that of the ear canal, so the core 20 does not come into contact with the ear canal. Figure 2 shows an alternative earphone 101. Equivalent elements have been given the same reference numerals as used in figure 1(a) and 1(b). In this earphone

101, the second portion 22 of the core 20 only has a single ridge 28 and a single groove 30, and the first portion 21 of the core 20 is partly of hemispherical shape, from which projects a rod 34 at whose opposite end is a circular flange 35 defining a flat end face 23. The rod 34 may for example be of diameter 1 mm. As described above, an acoustic driver 25 is secured onto the flat end face 23 of the core 20 by a plastic sleeve 26. In this earphone 101 the second cylindrical portion 22 does not extend so far into the wearer's ear canal.

Figure 3 shows an alternative earphone 102. Equivalent elements have been given the same reference numerals as used in figure 1(a) and 1(b). In this earphone

102, the second portion 22 of the core 20 has a single ridge 28 and a single groove 30, and the first portion 21 of the core 20 defines a first flange 36, from the centre of which projects a conically-tapered rod 37 that widens out, and at whose opposite end is a flat end face 23. The tapered rod 37 may for example have a minimum diameter of 1 mm where it joins the first flange 36. As described above, an acoustic driver 25 is secured onto the flat end face 23 of the core 20 by a plastic sleeve 26. In this earphone 102 the second cylindrical portion 22 does not extend so far into the wearer's ear canal, compared to the earphone 10 of figures la and lb.

Figure 4 shows an alternative earphone 103. Equivalent elements have been given the same reference numerals as used in figure 1(a) and 1(b). In the earphone 103, the second portion 22 of the core 20 has ridges 28 and 28a and two

circumferential grooves 30, and the first portion 21 of the core 20 defines a first flange 46, from the centre of which projects a narrow cylindrical rod 47 at whose opposite end is a second flange 48 defining a flat end face 23. The core 20 is shown in side view. The cylindrical rod 47 may for example have a diameter of 1.5 mm or 2.0 mm. The second portion 22 of the core is surrounded by a tubular suspension cap 40 which is shown in section; it is shown in its compressed state as it is when inserted into the ear canal, in which the external diameter of the tubular suspension cap 40 is substantially the same as that of the first flange 46. The uncompressed state of the tubular suspension cap 40 is indicated in broken lines. An end 32 of the second portion 22 is exposed, as it is not enclosed within the suspension cap 40. In the earphone 103 an acoustic driver 25 (shown in elevation) is secured onto the flat end face 23 of the core 20 by adhesive. The acoustic driver 25 may comprise an exciter coil, and this exciter coil may be bonded by the adhesive directly to the flat end face 23 of the core 20, or alternatively the acoustic driver may comprise an exciter coil within a casing with an end plate or end membrane driven by the acoustic driver, and the outer face of the end plate or end membrane may be bonded by the adhesive directly to the flat end face 23 of the core 20. Referring now to figure 5a, an earphone 104 is a modification to the earphone 103 in which the acoustic driver 25 is fixed for example by adhesive to a disc magnet 50 of the same diameter, and at least the second flange 48 is of ferromagnetic material, so that the acoustic driver 25 is held onto the core 20 magnetically. This arrangement makes it possible for the user to remove the acoustic driver 25 from the earphone 104, and to replace it subsequently.

Referring now to figure 5b, an earphone 105 is an alternative modification to the earphone 103, in which the acoustic driver 25 is enclosed within a close-fitting resilient silicone rubber container 52, closed at one end and with a restricted opening at the other end defined by an annular flange 53, the annular flange 53 being an integral part of the container 52 and engaging with the face of the second flange 48 further from the acoustic driver 25, such that the container 52 securely holds the acoustic driver 25 against the flat end face 23 of the core 20. This arrangement is comparatively straightforward to manufacture.

Referring now to figure 5c, an earphone 106 is another alternative modification to the earphone 103, in which the acoustic driver 25 is enclosed within a rigid container 54 which may be of metal, closed at one end and with a restricted opening at the other end defined by an annular flange 55; the annular flange 55 may for example be connected onto the open end of the rigid container 54 by a screw thread or a clip (not shown). An annular compression spring 56 (shown

schematically) locates between the annular flange 55 and the face of the second flange 48 further from the acoustic driver 25, pushing the annular flange 55 away from the second flange 48, and the acoustic driver 25 is therefore securely held against the flat end face 23 of the core 20. The exact design of the earphone 10, 101 to 106 can be balanced between comfort, simple insertion/removal and sound attenuation required by the user. The earphones feel extremely comfortable to use, as it is only the tubular suspension cap 40 that is in contact with the ear canal. Careful design of the earphone 10, 101 to 106 means that the core 20 need never touch the user's skin. The core 20 therefore may be described as acting as a floating isolator. In use, the exterior of the first cylindrical portion 21 of the core 20 will sit just on the outside of the ear canal to block ambient sound from reaching the user's ear. Hence the user hears only the sound created by the driver 25 and emitted from the end face 32 of the core 20.

In each of the earphones 101 to 106, as with the previously-described earphone 10, the solid core 20 is made of a non-compressible rigid and dense material, for example a metal such as steel, titanium or aluminium, or any other suitable metal, or from a ceramic material, or any other rigid material of suitable density. Although in applications where ambient sound suppression is particularly necessary, use of a comparatively dense material such as steel or titanium for the solid core 20 is advantageous, in some contexts it may be preferable to use a somewhat less dense material, for example a ceramic or hard plastic in preference to a metal, as this may enhance sound sensitivity, particularly at high frequencies. The tubular suspension layer 40 is made of a compressible material such as foam, memory foam, silicone or rubber; such a material has a significantly lower density and a much lower modulus of elasticity than the material of the solid core 20. In each of the earphones 10 and 101 to 106 the tubular suspension layer 40 may be disposable and can be replaced when required, whereas the core 20 is repeatedly re-usable.

It will be appreciated that a number of other modifications may be made, for example the earphone 10 might have a first portion 21 comprising a hemispherical section, a thin rod 34 and a flange 35 as shown in figure 2, instead of being of cylindrical shape; or might have a first portion is shown in figure 3 with a first flange 36 and a conically tapered rod 37. Other variations and modifications will be apparent to the skilled person.

Such variations and modifications may involve equivalent and other features that are already known and which may be used instead of, or in addition to, features described herein. Features that are described in the context of separate

embodiments may be provided in combination in a single embodiment. Conversely, features that are described in the context of a single embodiment may also be provided separately or in any suitable sub-combination.

It should be noted that the term "comprising" does not exclude other elements or steps, the term "a" or "an" does not exclude a plurality, a single feature may fulfil the functions of several features recited in the claims and reference signs in the claims shall not be construed as limiting the scope of the claims. It should also be noted that the Figures are not necessarily to scale; emphasis instead generally being placed upon illustrating the principles of the present invention.