earphone

Abstract

There is provided an earphone. The earphone comprises: a front cavity and a back cavity separated by a divider including a driver, the front cavity being engageable with a user; and a tube providing a port in the back cavity, openings at opposing ends of the tube connecting the port between the back cavity and an outside of the back cavity. The tube has sides between the openings, at least a part of the sides having an acoustically resistive opening. A corresponding headphone set, tube and method of manufacture is able to be provided.

Description

[0001] EARPHONE

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to earphones, such as to closed-back earphones, typically including sets with bass compensation mechanisms.

[0004] BACKGROUND

[0005] Earphones have a variety of configurations. Generally speaking, however, while the size and shape vary from model to model, between types and between manufacturers, the structure is the same across all earphone types. This structure includes a driver, typically in the form of a loudspeaker, that is supported. The driver provides at least part of a divide between a back cavity or volume and a front cavity or volume, which the driver-orientated with the diaphragm facing into the front cavity and its frame and yoke orientated towards the back cavity.

[0006] The front cavity is orientated towards a user’s ear in use, and has an open side or portion used to direct output into the user’s ear. The back cavity provides a space used to provide acoustic balance and tuning in conjunction with the front cavity.

[0007] Earphones have open-back and closed-back configurations. In an open-back configuration, the back cavity is surrounded partially or fully with an acoustically transparent or semi-transparent cover. Depending on the location of acoustically transparent sections, these connect the front cavity and back cavity, connect the back cavity with the external environment, or both.

[0008] On the other hand, in closed-back configurations, the back cavity has a cover that is not acoustically transparent, i.e. that is acoustically opaque, and thus does not provide a connection with any point outside the back cavity. To provide perfect acoustic performance, this also means the front cavity similarly needs an acoustic opaque surround.

[0009] In practice, perfect acoustic performance is difficult to achieve. This is because the front cavity cannot be sealed to the same degree as is possible with the back cavity. This is due to the front cavity needing to engage the user’s ear or head. Users have different shape heads and ears, or hair or spectacles are present where the front cavity meets the user’s head or ear. This means any seal with the user to close the front cavity has a tendency to leak.

[0010] Leaks from the front cavity typically cause a reduction in bass performance of the earphone. To account for this, a controlled leak is provided in the back cavity to tune the back cavity performance and correct the overall performance of the earphone by counteracting the reduction in performance of the front cavity.

[0011] A known means of achieving this is to provide an opening or port in the back cavity. Simply providing a hole is typically not enough to tailor the response to the specifics of the respective earphone, however. To address this the opening takes the form of a tube, such as shown in the known example of Figure 2. The length and diameter of the tube are chosen to tune the back cavity to provide increased bass performance to counteract the reduction in bass performance caused by front cavity leak.

[0012] However, as can be seen from Figure 3, simply providing a tuned tube provides a dip between the bass region of the frequency distribution and high frequency regions. This is undesirable in some circumstances. A known means of addressing this is to provide acoustically resistive covers at each end of the tube, such as shown in the known example of Figure 4. This provides damping to limit the dip. As can be seen from Figure 5, this damps the enhanced bass performance as well, limiting the effectiveness of the tube. This is also undesirable.

[0013] A further alternative is to provide an additional opening or port without a tube, the opening having an acoustically resistive covering. However, for this to function effectively, the opening needs to be large, which causes passthrough of external noise through the earphone to the user. This is not wanted by users, and is typically only able to be mitigated partially through use of active noise cancelling. Accordingly, there is a desire to enhance bass performance while maintaining performance across the rest of the frequency range and overall audible output.

[0014] SUMMARY OF INVENTION

[0015] According to a first aspect, there is provided an earphone comprising: a front cavity and a back cavity separated by a divider including a driver, the front cavity being engageable with a user; and a tube providing a port in the back cavity, openings at opposing ends of the tube connecting the port between the back cavity and an outside of the back cavity, the tube having sides between the openings, at least a part of the sides having an acoustically resistive opening.

[0016] Instead of providing a tube with sides that provide a barrier to air passage, this provides at least a portion of the sides with an opening that allows air to pass through it in a restricted manner. We have found this allows enhanced bass performance to be achieved that has a minimal dip in performance in the transition to higher frequencies. Further, this also avoids reduced enhancement that occurs when the openings at the tube ends have acoustic resistors. Accordingly, this provides a means to moderate the dip to enhance performance over the entire frequency spectrum.

[0017] The acoustically resistive opening may extend along any portion of the length of the tube. Typically, the at least a part of the sides having the acoustically resistive opening is at least a third of the length of the sides. We have found that this proportion provides sufficient enhancement in bass performance to counteract the reduction in bass performance caused by leaks from the front cavity in use while also limiting the dip. At proportions that extend along less of the length, the effect is less noticeable. The ratio of a damped length of the tube (such as one provided by the length of the tube with the acoustically resistive opening) to a closed part of the tube (i.e. a length of the tube without an acoustically resistive opening) sets the extent to which the dip in the frequency response is damped (i.e. the amount by which the dip is reduced). In testing we have found that suitable damping is achieved up to a ratio of 2 to 1 of closed tube length to acoustically resistive opening length. When not extending along the whole length of the tube, the acoustically resistive opening may be located at a portion of the tube sides distal to the back cavity.

[0018] Typically, the tube has openings at opposing ends.

[0019] The length of the acoustically resistive opening relative to the length of the tube may be up to only half or three quarters. However, typically, the at least a part of the sides having the acoustically resistive opening is a full length of the sides. As such, this allows a whole side of the tube to be provided by the acoustically resistive opening. This makes fabrication simpler and more efficient, and we have found this allows the total length of the tube to be kept to a minimum, thereby using as little as possible of the restricted space available in an earphone.

[0020] The width of the acoustically resistive opening relative to the perimeter of the sides, such as the perimeter perpendicular to the length of the tube, may be any width. Typically, the at least a part of the sides having the acoustically resistive opening has a width of at least a quarter of the perimeter of the sides (such as the perimeter perpendicular to the length of the tube). This provides a minimum width of the acoustically resistive opening. We have found a width of at least this proportion of the perimeter provides suitable tuning for the tube and the bass enhancement.

[0021] By the term “perimeter”, we intend to mean the internal perimeter of the tube rather than a perimeter of the outside of the tube, which would then take into account the thickness of the tube sides or any wall(s) providing the tube sides.

[0022] The width of the acoustically resistive opening may be up to the full perimeter of the sides (perpendicular to the length of the tube). Typically, the at least a part of the sides having the acoustically resistive opening has a width of up to a third of the perimeter of the sides (perpendicular to the length of the tube). We have found that a width of up to this proportion provides suitable tuning for the tube and its effects while allowing the tube to maintain its form and for manufacture to be practical. Typically, the earphone is a closed-back earphone. This increases the bass enhancement provided by the tube since pressure equalisation is provided (exclusively) by passage of air within and / or through the tube, allowing dedicated tuning of the tube parameters to the specifics of the earphone.

[0023] The tube may extend away from the back cavity, such as by the length being orientated normal to a surround to the back cavity. Typically though, the tube extends laterally relative to the back cavity. This reduces the volume required for the earphone components since additional space does not need to be provided for the tube’s length to extend away from the back cavity.

[0024] The earphone may be arranged such that the front cavity, the back cavity, and the tube are aligned with one another, such as along an axis, for example passing through the divider and a surface of the back cavity distal to the front cavity and, optionally, through an opening of the front cavity (i.e. at a face of the front cavity distal to the back cavity). This arrangement simplifies fabrication of the earphone. As an example of the alignment, the front cavity, the back cavity, and the tube may be aligned in a direction that is lateral to a user’s head when the earphone is in use.

[0025] The tube may extend from a surface of the back cavity, such as extending along a surface of the back cavity. This may be any of the surfaces of the back cavity that is not at the divider. The tube may be arranged such that an end of the tube that is fluidically connected to the back cavity is provided at the surface of the back cavity, and an opposing end of the tube that is fluidically connected to the outside of the back cavity is provided away from the back cavity. That is, the tube’s geometry may be outside the back cavity apart from at the opening of the tube that is provided at the surface of the back cavity. By defining a clear boundary between the back cavity and the tube in this way, pressure equalisation is improved. Moreover, tuning of the tube parameters and manufacturing the tube is simpler.

[0026] The tube may be provided at a back surface of the back cavity, the back surface being opposite the divider. That is, the divider may be the surface at which the driver is provided, and the back surface may be a surface opposite to the divider. An opening may be provided in the back surface of the back cavity, such as a surface distal to the front cavity, the opening being one end of the tube. This results in greater ease of manufacturing since the tube can be provided directly behind the back section, simplifying the alignment and positioning of the tube.

[0027] The tube may extend from the opening in the back surface of the back cavity. The tube may extend entirely external to the back cavity. That is, one end of the tube may be provided at the opening in the back surface of the back cavity, and an opposing end of the tube may be provided away from the back cavity such that the tube is provided external to the back cavity, and the tube is not part of the back cavity, such as being (entirely) outside the back cavity. This improves accessibility during manufacturing of the tube, resulting in a simpler manufacturing process.

[0028] The tube may be a distinct component from the back cavity or other components of the earphone, such as due to it being a separable component or a component that is added during manufacture, such as by being an independent component that is then attached or joined to the other components during manufacture. However, typically, the tube is provided by a channel in a surround of the back cavity, sides of the tube being walls of the channel. This allows positioning and the overall volume of the port, of which the tube provides a component, to be repeatable and reliable and simplifies the process of constructing the earphone. Further, this allows the channel to be integral with the surround, meaning the channel does not need independent placement on the earphone during construction.

[0029] The channel may provide the sides of the tube. In such an arrangement, the channel thus has an opening to provide the acoustically resistive opening. This opening may be on any side of the channel. Typically, the channel has a top opening opposite a (channel) base, an acoustically resistive material being positioned at the top opening, the top opening thereby providing the acoustically resistive opening. This opening may be flush with the back cavity surround or may stand proud (i.e. may be above or elevated relative to the surround). By having a top opening as the region where the acoustically resistive material is provided, this provides an accessible position at which to add the material. This reduces manufacturing complexity since it allows easy access to the location where the acoustically resistive material is to be placed.

[0030] The port may be between the back cavity and any point outside the back cavity, such as the front cavity. Typically, however, the tube connects the port between the back cavity and outside of the earphone. This allows pressure equalisation between the back cavity and an exterior of the earphone, which is desirable for enhancing bass performance.

[0031] While the acoustically resistive opening may provide an opening between the tube and the back cavity, typically, the acoustically resistive opening provides an opening between the tube and (an) outside of the back cavity. This avoids the acoustically resistive opening causing interference in the back cavity or vibrations in the back cavity passing into the acoustically resistive opening, causing interference in the tube with vibrations originating at an opening of the tube.

[0032] The acoustically resistive opening may be provided external to the back cavity. For example, the acoustically resistive opening may be provided entirely external to the back cavity. This can further avoid causing interference in the back cavity due to the acoustically resistive opening, while also simplifying manufacturing of the tube and the acoustically resistive opening.

[0033] The acoustically resistive opening may provide an opening between the tube and front cavity and / or another location. Typically, the acoustically resistive opening provides an opening between the tube and (an) outside of earphone. This means the acoustically resistive opening has limited interference from other parts of the earphone, allowing the opening to be kept to a minimum size to achieve suitable effects.

[0034] The acoustically resistive opening may be provided by an opening at which acoustically resistive material is located. The acoustically resistive material may be a woven material, fabric, plastic or metal. When plastic, such as nylon, or metal, the acoustically resistive material may be a mesh. Typically, the acoustically resistive material is paper, such as an acoustically resistive paper.

[0035] The acoustically resistive material may have an acoustic resistance between about 5 MKS Rayls and 800 MKS Rayls, between about 10 MKS Rayls and 600 MKS Rayls, between about 50 MKS Rayls and 300 MKS Rayls, such as about 100 MKS Rayls.

[0036] The channel may have a length (such as a length of a mid-line of the channel or tube) of between 5 millimetres (mm) and 100 mm, between 10 mm and 60 mm, between 15 mm and 30 mm, such as 22 mm.

[0037] The tube and the channel may be the same length and / or width and / or depth. The tube may have a length (such as a length of a mid-line of the tube) of between 5 mm and 100 mm, between 8 mm and 50 mm, between 10 mm and 25 mm, such as 12 mm.

[0038] The width of the tube (such as the distance across the tube perpendicular to the length of the tube along the tube mid-line) may be between 0.5 mm and 10.0 mm, between 1 .0 mm and 4.0 mm, between 1 .5 mm and 3.0 mm, such as 2 mm.

[0039] The depth or height of the tube (such as the distance between a base and top, or top opening as defined above perpendicular to the length of the tube along the tube mid-line) may be between 0.1 mm and 10.0 mm, between 0.5 mm and 4 mm, between 0.7 mm and 2 mm, such as 1 mm.

[0040] An opening of a tube at the back cavity, such as the aperture referred to below may have a width (such as a diameter) of between 0.1 mm and 10.0 mm, between 0.5 mm and 5.7 mm, between 1 .0 mm and 4 mm, such as 2 mm. This may be the same as the width and / or depth of the tube or channel. When considering the velocity of air in the tube in the range expected during normal use of the earphone (i.e. within typical operational bounds) a transition from laminar air flow to turbulent air flow through the tube occurs when the width is less than this, such as less than 1.0 mm. This leads to an amplitude dependent non-linear acoustical resistance and causes odd-order harmonic distortions. This can also apply to the width of the acoustically resistive opening.

[0041] The back cavity may have a volume of between 100 cubic millimetres (mm3, mmA3) and 4000 mmA3, between 150 mmA3 and 3500 mmA3, 300 mmA3 and 1000 mmA3, such as 670 mmA3.

[0042] According to a second aspect, there is provided a headphone set comprising at least one earphone according to the first aspect.

[0043] The headphone set may have only a single earphone. Typically, the headphone set has a pair of earphones.

[0044] The pair of earphones may include only a single earphone according to the first aspect (and one other earphone). Typically, however, each of the earphones of the pair of earphones, typically, may be an earphone according to the first aspect.

[0045] Typically the headphone set includes a headband connected to each earphone. When there is a plurality of earphones these are typically connected to distal to each other earphone.

[0046] According to a third aspect, there is provided a tube suitable for providing a port in a back cavity of an earphone according to the first aspect, the tube comprising sides and openings at opposing ends providing a port between the openings, at least a part of the sides having an acoustically resistive opening.

[0047] Typically, the tube is suitable for use with a headphone set according to the second aspect.

[0048] According to the fourth aspect, there is provided a method of manufacturing an earphone according to the first aspect, the method comprising: forming a housing; providing a divider in the housing, a back cavity being formed between a side of the divider and the housing and a front cavity being formed on an opposing side of the divider; providing, at the housing, a channel with an aperture, the aperture opening into the back cavity and the channel having an at least partially open side; and providing, at an open portion of the at least partially open side, an acoustically resistive material, the aperture being in an enclosed portion of the channel, the channel and acoustically resistive material forming a tube, the tube providing a port between the back cavity and an outside (or exterior) of the back cavity.

[0049] The divider may be provided in the housing by any means, such as by being added after fabrication of the housing, or during fabrication of the housing. This may be by simultaneous fabrication, such as moulding or (3D) printing, or by being joined as part of fabrication. Typically, the housing may be shaped to accept a divider within the housing. This allows the divider to be fitted after fabrication of the housing.

[0050] The channel may be provided in the housing, such as by being integral with the housing. The open side of the channel may be flush with (a surface of, such as an external surface of) the housing.

[0051] The acoustically resistive material may partially or fully close the open portion of the open side of the channel, or may partially or fully close the open side of the channel.

[0052] Regardless of the relevant aspect, the earphone may have an outer casing. The outer casing may be provided over some or all of the housing and / or surround of the back cavity. This may be a closed casing, such as to prohibit air passage between an outside and inside of the casing. Typically, however, the casing may permit air passage between an outside and inside of the casing, such as by an opening, grill or mesh.

[0053] BRIEF DESCRIPTION OF DRAWINGS

[0054] Example earphones, headphone sets, tubes and methods of manufacture are described in detail below with reference to the drawings, in which:

[0055] Figure 1 shows a schematic of an example headphone set;

[0056] Figure 2 shows a schematic of a first prior art example earphone;

[0057] Figure 3 shows a schematic of a second prior art example earphone; Figure 4 shows a plot of sound output level against frequency for the first prior art example earphone;

[0058] Figure 5 shows a plot of sound output level against frequency for the second prior art example earphone;

[0059] Figure 6 shows a schematic of a first example earphone;

[0060] Figure 7 shows a schematic of a second example earphone;

[0061] Figure 8 shows a plot of sound output level against frequency for an example earphone;

[0062] Figure 9 shows a schematic of a third example earphone; and Figure 10 shows a schematic of a fourth example earphone.

[0063] DETAILED DESCRIPTION

[0064] In accordance with an aspect, in the example shown in Figure 1 , there is a headphone set generally illustrated at 1. This is intended for placement over a user’s head (not shown).

[0065] The headphone set 1 , in this example, has two earphones 10 in the form of earcups. The earcups are connected by a headband 20. This holds the earcups in position relative to each other. Typically, the earcups are arranged so that they are aligned with the user’s ears (not shown) so as to rest against or over the user’s ears during use.

[0066] In some examples, instead of having two earcups 10, the headphone set 1 has (only) a single earcup. In such examples, the headband 10 may still be present to hold the earcup to the user’s head.

[0067] In a further example, the headphone set 10 has earphones in the form of one or two earpieces that sit in the user’s ear(s) in use. In such examples, the headband is typically not present, but other supports may be used, as is also possible as an alternative to the headband 20 shown in the example of Figure 1 .

[0068] In the example shown in Figure 1 , the earcups 10 each have an ear pad 30, which can also be referred to as ear cushions, cushioning or an acoustic baffle. These sit against the user’s ear or head in use. The ear pads can either be permeable to air or can be intended to be impermeable to air, meaning they are intended not to allow air to pass through them from one side to the other.

[0069] The earcups 10 of the example shown in Figure 1 also each have a cover 40. This provides a shell that is externally facing in use. Typically, this cover is acoustically transparent (or permeable) or partially acoustically transparent. This is achieved, in some examples, by the cover being designed to have limited or minimum acoustic impact, making it at least partially acoustically transparent or as acoustically transparent as possible. This assists in providing consistency between pairs of earphones (for example left-right pairs) when a cable is connected in one earphone of a pair and not into the other earphone of the pair, which may then have an open port. In other examples, while some passage of air into and out of the shell is possible, the cover is intended to be acoustically opaque, such as being acoustically non-transparent.

[0070] To address reduced bass performance due to leaking where earphones rest against a user, there are various known examples of earphones. Two such known examples are shown in Figures 2 and 3.

[0071] The known example shown in Figure 2 shows an earphone 1000. This has a front cavity 1100 and a back cavity 1200 separated by a divider 1300, in which a driver 1400, also referred to as a loudspeaker, is located. This driver is orientated to direct sound into the front cavity during use.

[0072] The known example shown in Figure 2 is a closed-back earphone 1000. In view of this, the back cavity 1200 is sealed, not permitting passage of air in or out of the cavity.

[0073] The front cavity 1100 is also intended to be sealed in the same manner. However, in use, this sits against a user 1500, typically against their head or ear, with the user providing one side of the surround to the front cavity. For comfort and to assist with fit, the surround of the front cavity is often provided with cushioning (not shown) where the surround rests against the user in use. While this cushioning deforms to the shape of the user’s head or ear to provide a fit with the user, the fit is not perfect. This is due to it not being possible to provide a mass-produced earphone that fits all users equally well, and due to hair, spectacles and / or other attributes of the user. As such, the front cavity leaks at the join between the surround and the user. In other words, air is able to pass through gaps at this point. As noted above, this causes a reduction in the amplitude of the bass frequencies audible to the user during use.

[0074] To counteract this, the back cavity 1200 is provided with a tube 1600. This so- called “bass tube” connects the back cavity with the air outside the back cavity. In terms of how this functions, by tailoring selection of the length and diameter of the tube to the specific sizes of the back cavity and front cavity 1100, the diaphragm 1410 of the driver 1400 does not have to compress the rear volume in the effective frequency range of the bass tube. This means the diaphragm is able to make larger strokes in this frequency range. This leads to higher sound pressure in the front cavity, and thus compensates for the reduction in bass performance, also referred to as “bass roll-off’, with the effect produced by the tube also being referred to as “bass boost”.

[0075] The frequency at and below which the bass tube is active is determined by the acoustic inductance of the bass tube and the effective acoustic capacitance (including parts of the mass of the diaphragm of the transducer) of the back cavity.

[0076] However, if this arrangement is used without other acoustically effective elements, there will be a dip in the frequency response of the headphones at the end of the falling slope of the boosted bass range. This is demonstrated by the plot shown in Figure 4. This shows decibels (dB) on the y-axis against frequency on the x- axis.

[0077] This shows that at 20 hertz (Hz), the bass boost is about 20 dB above a flat distribution. This slopes in a curve with a steadily increasing negative gradient to a minimum inflection point of about -10 dB at about 101 Hz. This thus represents an attenuation instead of an amplification of the output. The slope then increases back towards 0 Hz with a steadily decreasing positive gradient. To counteract this effect, the known earphone example of Figure 3 is used. This has an identical arrangement as the known earphone example of Figure 2, and, as such, the same reference numerals are used for identical features.

[0078] For confirmation, the known closed-cup earphone 2000 of Figure 3 has a front cavity 1100 and a back cavity 1200 separated by a divider 1400 in which a driver 1410 is located and orientated to direct sound into the front cavity. One side of a surround of the front cavity is provided by a user 1500 in use.

[0079] To provide a bass boost, a bass tube 1600 is connected to the back cavity. The bass tube 1600 has openings at each end.

[0080] In the known example of Figure 3, the bass tube has acoustic resistors 1610,1620 at each end. This provides damping of the filter the bass tube provides. The acoustic resistance also closes the bass tube to the ambient air, however. This reduces the effectiveness of the bass boost. To avoid this, a longer tube with a wider diameter can be used, but that is difficult in relatively small headphone dimensions and the tube length would need then to have dimensions at which audible acoustical resonances occur.

[0081] The overall effect of the known example of Figure 3 is shown in the plot of Figure 5. As with Figure 4, this shows decibels on the y-axis against frequency on the x- axis.

[0082] At 20 Hz, the bass boost produced is about 8 dB, which reduces in an S-curve (i.e. in a similar shape to a sigmoid function) to 0 dB from about 120 Hz and higher. Unlike the known example of Figure 2, the known example of Figure 3 can be seen not to have a dip close to 100 Hz, or elsewhere.

[0083] To counteract the dip and limited bass boost capability of the known examples of Figures 2 and 3, we have developed a further earphone.

[0084] An earphone according to an aspect is generally illustrated at 100 in Figure 6. As an earphone, this has the same general structure as the known example earphones shown in Figures 2 and 3. This structure is, namely, a front cavity 110 and a back cavity 120, separated by a divider 130.

[0085] In some examples, the earphone 100 is a closed-back earphone. As such, the divider 130 prevents passage of air between the front cavity and back cavity. In other examples, air passage across the divider may be possible, such as if the earphone is an open-back earphone.

[0086] In various examples, the divider 130 has a driver 140 connected to it. This is orientated to direct sound into the front cavity 110 in use. This is achieved by the diaphragm 141 of the driver being in a side of the front cavity and a frame and / or yoke or holder of the driver being in a side of the back cavity 120.

[0087] The front cavity 110 has an open side in several examples. In use, this is placed against a user 150 to close the front cavity. This is achieved by placing a surround of the front cavity against the user, the surround having cushioning (not shown) in various examples to provide a fit with the user.

[0088] As noted above, this fit with the user 150 typically is not perfect, so causes a bass drop-off. This is counteracted by, in some examples, the back cavity 120 having a port provided by a tube 160.

[0089] In several examples, the tube has opposing ends at which there are openings. One of the openings provides an opening into the back cavity 160. In various examples, the other opening provides an opening to an exterior of the back cavity.

[0090] In the example shown in Figure 6, the opening to an exterior of the back cavity is an opening to an exterior of the earphone 100. In some examples, this is provided by the opening being a direct opening to an exterior of the earphone. In other examples, this is provided by a passage (not shown) between the opening and an exterior of the earphone that does not act as a port, waveguide or other acoustic feature. In various examples, the opening is an opening into the inside of an (outer) casing of the earphone. This has an opening, such as a grill, mesh or aperture that allows passage of air in and out of the casing from outside of the earphone and acts like the passage in that it does not act as a port, waveguide or other acoustic feature due to its shape and / or size.

[0091] In various examples, the tube 160 has an acoustic resistive opening 162 along its length. In the example in Figure 6, the acoustic resistive opening extends along the whole length of one side of the tube. In other examples, the acoustic resistive opening extends along only a part of the length of the tube and / or on two or more sides of the tube.

[0092] The acoustic resistance of the acoustic resistive opening 162 is provided, in some examples, by an acoustic resistor, such as an acoustically resistive paper. In other examples, this is a mesh or grid, such as a plastic, fabric or metal mesh or grid.

[0093] A corresponding example is shown in Figure 7. This shows an earphone 100’ with a similar arrangement to the example shown in Figure 6. As such, this has a similar front cavity 110’ and back cavity 120’ separated by a divider 130’ with a similarly orientated driver 140’ and diaphragm 14T.

[0094] In the example shown in Figure 7, the surround of the front cavity 110’ sits against a user 150’ in used. In Figure 7, small gaps 152’ are shown to indicate the fit of the surround allowing air passage between the exterior of the earphone 100’ and the front cavity. The engagement of the front cavity with the user is otherwise identical to that described above.

[0095] There is a difference in presentation between the example shown in Figure 6 and the example shown in Figure 7. In the example shown in Figure 7, there is a tube 760 providing a port between the back cavity 120’ and an outside of the back cavity. The difference between the example shown in Figure 6 and the example shown in Figure 7 is that the tube is orientated with its length running laterally relative to the back cavity. This is instead of, as is illustrated in Figure 6, the length of the tube extending away from the back cavity.

[0096] In some examples with the tube 760 being orientated laterally, such as in the example shown in Figure 7, a side of the tube orientated away from the back cavity 120’ has an acoustically resistive opening 762. In various examples, an acoustically resistive material is provided at the acoustically resistive opening. As described above in relation to Figure 6, in several examples, the acoustically resistive material is an acoustic resistor, such as an acoustically resistive paper. In other examples, this is a mesh or grid, such as a plastic, fabric or metal mesh or grid.

[0097] In the example shown in Figure 7, the acoustically resistive opening 762 is provided along a whole length of the side. In other examples, the acoustically resistive opening is provided along only a portion of the length of the side. This can be at the back cavity end or end of the tube proximal to the back cavity, but is typically at the opposing end, so the end of the tube distal to the back cavity.

[0098] When the tube 760 is arranged with its length laterally relative to the back cavity 120’, in various examples, the passage the tube provides is not straight along the mid-line of the tube. Instead, the passage has at least one bend. This is because the tube has a back cavity proximal end opening 764 providing an opening at the back cavity connecting the back cavity to the tube and a back cavity distal end opening 766 connecting the tube to an outside of the back cavity.

[0099] In other examples, the tube 760 has different shapes, such as only having one bend due to one of the openings 764, 766 being on another side to orientate the opening perpendicular to the other opening. Alternatively or additionally, the tube itself has one or more bends in several examples.

[0100] Further, in the example shown in Figure 7, the tube 760 is connected to the surround of the back cavity 120 at a side of the back cavity opposite a side provided by the divider 130. In other examples, the tube is able to be located elsewhere. In some examples, this is on a side of the surround of the back cavity.

[0101] As described in more detail below in relation to Figure 9 and Figure 10, in some examples with the tube 760 orientated laterally relative to the back cavity 120, the tube provided by a channel 940 in a surround 920 of the back cavity. This enables use of an existing component to house the tube rather than requiring an additional component to be added. In various examples, this allows the proximal end opening 764 to be provided by an aperture 960 in the surround.

[0102] In some examples, the acoustic resistor at the acoustically resistive opening 762 provides a damping of 100 MKS Rayls. In several examples, this has a length of about 12 mm.

[0103] In various examples, the tube 760 has a length of about 22 mm. In some examples, this corresponds to a length along a mid-line of the tube.

[0104] In several examples, the tube has a square or rectangular cross-section perpendicular to the length of the tube. In other examples, this cross-section is circular.

[0105] Considering various examples of a tube 760 with a rectangular cross-section, such a tube has a depth / height of about 1 mm. In such examples, the depth / height is the distance within the tube between the acoustically resistive opening 762 and an opposing surface of the tube, such as the base of the tube.

[0106] Similarly, in several examples of a tube 760 with a rectangular cross-section, such a tube has a width of about 2 mm. In various of those examples, the width is the distance within the tube between sides perpendicular to the acoustically resistive opening 762, perpendicular to the length of the tube and perpendicular to the depth / height of the tube.

[0107] In some examples, the proximal end opening 764 is round. In various of those examples, the proximal end opening has a diameter of about 2 mm.

[0108] The above parameters provide a volume over which the acoustic resistor extends of about 24 mmA3. This compares, in some examples, to a volume of the back cavity 120’ of about 670 mmA3.

[0109] In examples implementing these parameters, along with various other examples implementing similar arrangements to Figure 6 and Figure 7, this provides a response as shown in the example plot of Figure 8. In Figure 8, a plot is shown with decibels on the y-axis against frequency on the x-axis.

[0110] The example plot of Figure 8 shows a similar shape curve to the curve shown in Figure 5. However, in this example, the enhanced bass performance has a larger amplitude. This is because the plot shows an S-curve or sigmoid function with a value of about 20 dB at 20 Hz, dropping to 0 dB by about 350 Hz, with the value approaching 0 dB from about 122 Hz. This shows a bass boost effect similar to that achieved in the example of Figure 2 rather than the reduced effect achieved in the example of Figure 3, but without the dip of the example of Figure 2. As such, this shows an improved overall performance.

[0111] Turning to Figure 9 and Figure 10, these show examples that demonstrate how an example earphone according to an aspect is assembled.

[0112] To manufacture an earphone 900, 900’ shown in the examples of Figure 9 and Figure 10, a surround or housing 920, 920’ is formed by known means. Typically, this is formed by injection moulding, casting, printing or other known techniques.

[0113] In some examples the housing 920, 920’ is formed with a divider, and, in other examples, the divider is formed independently and then inserted into the housing, or at least a portion thereof, that is shaped to accept the divider. When in the housing, the divider forms a back cavity on one side of it and a front cavity on the other side. The divider is able to hold a driver, which is installed during manufacture.

[0114] In various examples, a channel 940, 940’ is formed in the housing 920, 920’. The channel is formed with the housing as it is formed in several examples. In other examples, the channel is formed in the housing after the housing is formed, such as by a further manufacture step of shaping or deforming the housing.

[0115] There are further examples where the channel is not part of the housing 920, 920’. Instead, in those examples, the channel is provided as a separate component that is joined to or inserted into the housing as a step during the manufacture or assembly process. In the example shown in Figure 9, an aperture 960 is shown at one end of the channel 940. This aperture is an opening through the housing 920 into the back cavity. This is formed in some examples by the aperture being drilled. In other examples, it is formed as part of the moulding process of the housing.

[0116] The aperture 960 is located at different points in the channel 940 in other examples. In some examples, this is at a different location in the base of the channel, such as partway along the length. In other examples, the aperture is provided on a side of the channel connected to the base, such as one of the upright sides.

[0117] In the examples shown in Figure 9 and Figure 10, the channel 940, 940’ is shown with rounded ends and with a length significantly longer than its width and depth. In other examples, the ends of the channel are a different shape, and / or the width and / or depth are larger or smaller relative to the length of the channel.

[0118] The examples of Figure 9 and Figure 10 show an acoustically resistive material 980, 980’ located over a portion of the channel 940, 940’. As can be seen from Figure 9, the acoustically resistive material 980, 980’ is also located over the aperture 960.

[0119] In some examples, the acoustically resistive material 980, 980’ is stuck to the housing 920, 920’. In various examples, this is stuck by an adhesive. The adhesive is double-sided adhesive tape in several examples. In other examples, other adhesives are used, of which glue is an example, or ultrasonic of heat bonding to the housing, such as a plastic housing, is used, typically when the acoustically resistive material is a plastic mesh.

[0120] To increase reliability of placement of the acoustically resistive material 980, 980’ during assembly, in some examples, the housing 920’ has a guide 982’ with which the acoustically resistive material is aligned as it is being stuck to the housing. This guide is a projection or rim on the housing in various examples. In other examples, this may be an etched, scored or drawn line. In some examples, the acoustically resistive material 980, 980’ has a boundary defining its perimeter. In various examples where adhesive tape is used as the sticking mechanism to stick the acoustically resistive material to the housing 920, 920’, this boundary is provided by the tape. At this boundary, the acoustically resistive material is acoustically (more) opaque than other portions of the acoustically resistive material.

[0121] With the acoustically resistive material 980, 980’ applied to the housing 920, 920’, all other parts of standard manufacture and assembly processes of earphones are completed. In some examples, some of these steps will be before and / or after the acoustically resistive material is applied to the housing. Depending on the type of earphone being produced, this includes one or more of: attachment of one or more earphones onto a headband, or, alternatively, forming the earphone into an earpiece or earbud, connection of one or more acoustic baffles, providing electrical connections, providing circuitry, providing passive and / or active noise cancelling components and connecting an outer casing.

[0122] As further options for some examples, in some examples according to an aspect, there is an acoustically resistive material at an end of the tube distal to the back cavity, such as to partially or fully cover the opening. Additionally or alternatively, in various examples, there is an acoustically resistive material at an end of the tube proximal to the back cavity, such as to partially or fully cover the opening.

[0123] In several examples, a further aperture is provided in the back cavity providing a further port between the back cavity and an outside of the back cavity. An acoustically resistive material is provided at this port that partially or fully covers the aperture.

[0124] In some examples, the tube or the tube sides are entirely formed of an acoustic resistor.

Claims

22CLAIMS1. An earphone comprising: a front cavity and a back cavity separated by a divider including a driver, the front cavity being engageable with a user; and a tube providing a port in the back cavity, openings at opposing ends of the tube connecting the port between the back cavity and an outside of the back cavity, the tube having sides between the openings, at least a part of the sides having an acoustically resistive opening.

2. The earphone according to any one of the preceding claims, wherein the tube extends laterally relative to the back cavity.

3. The earphone according to claim 2, wherein the front cavity, the back cavity, and the tube are aligned with one another.

4. The earphone according to any one of claims 2 or 3, wherein the tube is provided by a channel in a surround of the back cavity, sides of the tube being walls of the channel.

5. The earphone according to claim 4, wherein the channel has a top opening opposite a base, an acoustically resistive material being positioned at the top opening, the top opening thereby providing the acoustically resistive opening.

6. The earphone according to any one of the preceding claims, wherein the tube extends from a surface of the back cavity.

7. The earphone according to claim 6, wherein the tube extends along the surface of the back cavity.

8. The earphone according to claim 6 or claim 7, wherein the tube extends from a surface of the back cavity distal to the front cavity.

9. The earphone according to any one of the preceding claims, wherein the tube extends entirely external to the back cavity.

10. The earphone according to any one of the preceding claims, wherein the acoustically resistive opening provides an opening between the tube and the outside of the back cavity.11 . The earphone according to any one of the preceding claims, wherein the at least a part of the sides having the acoustically resistive opening is at least a third of the length of the sides.

12. The earphone according to claim 11 , wherein the at least a part of the sides having the acoustically resistive opening is a full length of the sides.

13. The earphone according to any one of the preceding claims, wherein the at least a part of the sides having the acoustically resistive opening has a width of at least a quarter of the perimeter of the sides.

14. The earphone according to any one of the preceding claims, wherein the at least a part of the sides having the acoustically resistive opening has a width of up to a third of the perimeter of the sides.

15. The earphone according to any one of the preceding claims, wherein the earphone is a closed-back earphone.

16. The earphone according to any one of the preceding claims, wherein the tube connects the port between the back cavity and outside of the earphone.

17. The earphone according to any one of the preceding claims, wherein the acoustically resistive opening provides an opening between the tube and outside of the back cavity.

18. The earphone according to 17, wherein the acoustically resistive opening provides an opening between the tube and outside of the earphone.

19. A headphone set comprising at least one earphone according to any one of the preceding claims.

20. A tube suitable for providing a port in a back cavity of an earphone according to any one of claims 1 to 18, the tube comprising sides and openings atopposing ends providing a port between the openings, at least a part of the sides having an acoustically resistive opening.21 . A method of manufacturing an earphone according to any one of claims 1 to 18, the method comprising: forming a housing; providing a divider in the housing, a back cavity being formed between a side of the divider and the housing and a front cavity being formed on an opposing side of the divider; providing, at the housing, a channel with an aperture, the aperture opening into the back cavity and the channel having an at least partially open side; and providing, at an open portion of the at least partially open side, an acoustically resistive material, the aperture being in an enclosed portion of the channel, the channel and acoustically resistive material forming a tube, the tube providing a port between the back cavity and an outside of the back cavity.

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