Abstract
There is provided a headrest housing a dipole loudspeaker for producing sound at bass frequencies in a forward direction and in a rear direction, a response 180 degrees out of phase from respective front and rear resonating surfaces. The headrest includes a waveguide formation to isolate sound from travelling through the headrest between the front surface and the rear surface. The headrest also includes an attachment formation, and the attachment formation suspends the first frame of the dipole loudspeaker and acts as a secondary suspension system. By including waveguide formations, the sound from the front surface of the dipole speaker can be guided outside of the headrest, wherein the shortest path from the front surface to the back surface is extended to be around the outside of the headrest. Guiding the sound path to be external to the headrest, prevents internal sound guiding compressing the intended path length.
Claims
1-15. (canceled)
16. An audio system comprising a dipole loudspeaker and a headrest; the dipole loudspeaker includes: a diaphragm having a first radiating surface and a second radiating surface, wherein the first radiating surface and the second radiating surface are located on opposite faces of the diaphragm; a drive unit configured to move the diaphragm at bass frequencies such that the first and second radiating surfaces produce sound at bass frequencies, wherein the sound produced by the first radiating surface is in antiphase with sound produced by the second radiating surface; a loudspeaker frame, wherein the diaphragm is suspended from the loudspeaker frame via a primary suspension system; and the headrest includes: a main body assembly shaped to include a first opening configured to allow sound produced by the first radiating surface to propagate out of a first side of the headrest, and a second opening configured to allow sound produced by the second radiating surface to propagate out of a second side of the headrest; a waveguide formation which is configured to direct sound produced by the first radiating surface out of the first opening, and to direct sound produced by the second radiating surface out of the second opening; and an attachment formation which is used to attach the loudspeaker frame to the headrest, wherein the attachment formation provide a secondary suspension system via which the loudspeaker frame is suspended.
17. The audio system of claim 16, wherein the main body assembly includes a foam structure, wherein the foam structure is acoustically resistive.
18. The audio system of claim 17, wherein a projecting element is formed of acoustically resistive foam.
19. The audio system of claim 18, wherein the projecting element is formed integrally to the foam structure.
20. The audio system of claim 18, wherein the waveguide formation is the projecting element and the projecting element extends to proximity with the frame, the projecting element and frame combine to form an acoustic baffle for guiding the sound.
21. The audio system of claim 18, wherein the waveguide formation is attached to the frame, the waveguide formation is the projecting element and the attachment formation is also the projecting element.
22. The audio system of claim 18, wherein the attachment formation is the projecting element, the projecting element including a distal end for attaching to a corresponding attachment formation on the loudspeaker frame and a stiffness of the projecting element being adapted to provide the secondary suspension system to suspend the loudspeaker frame.
23. The audio system of claim 22, wherein the projecting element includes an inserted component, the inserted component extending at least partially along a length of the projecting element to alter the stiffness of the projecting element.
24. The audio system of claim 23, wherein the inserted component extends from the distal end of the projecting element, and the loudspeaker frame is attached to the inserted component.
25. The audio system of claim 16, wherein the audio system is incorporated in a seat.
26. The audio system of claim 25, wherein the seat is incorporated in a vehicle.
27. A dipole loudspeaker for combining with a headrest to form an audio system, the dipole loudspeaker comprising: a diaphragm having a first radiating surface and a second radiating surface, wherein the first radiating surface and the second radiating surface are located on opposite faces of the diaphragm; a drive unit configured to move the diaphragm at bass frequencies such that the first and second radiating surfaces produce sound at bass frequencies, wherein the sound produced by the first radiating surface is in antiphase with sound produced by the second radiating surface; and a loudspeaker frame, wherein the diaphragm is suspended from the loudspeaker frame via a primary suspension system; wherein the loudspeaker frame is specifically adapted to include a corresponding attachment formation for attaching the loudspeaker frame to an attachment formation of a headrest.
28. The dipole loudspeaker of claim 27, wherein the corresponding attachment formation is a projection formed on the loudspeaker frame.
29. The dipole loudspeaker of claim 27, wherein the corresponding attachment formation is a cavity formed on the loudspeaker frame.
30. A method of assembling an audio system, wherein the method comprises assembling a dipole loudspeaker to a headrest; wherein the headrest includes: a main body assembly shaped to include a first opening configured to allow sound produced by the first radiating surface to propagate out of a first side of the headrest, and a second opening configured to allow sound produced by the second radiating surface to propagate out of a second side of the headrest; a waveguide formation which is configured to direct sound produced by the first radiating surface out of the first opening, and to direct sound produced by the second radiating surface out of the second opening; and an attachment formation; wherein the dipole loudspeaker includes: a diaphragm having a first radiating surface and a second radiating surface, wherein the first radiating surface and the second radiating surface are located on opposite faces of the diaphragm; a drive unit configured to move the diaphragm at bass frequencies such that the first and second radiating surfaces produce sound at bass frequencies, wherein the sound produced by the first radiating surface is in antiphase with sound produced by the second radiating surface; and a loudspeaker frame, wherein the diaphragm is suspended from the frame via a primary suspension system; wherein the loudspeaker frame is specifically adapted to include a corresponding attachment formation for attaching the loudspeaker frame to the attachment formation of the headrest; wherein the method comprises: moving the dipole loudspeaker relative to the headrest to cause the attachment formation of the headrest to couple to the corresponding attachment formation of the loudspeaker frame so that the attachment formation provide a secondary suspension system via which the loudspeaker frame is suspended.
Description
SUMMARY OF THE FIGURES
[0049] Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:
[0050] FIG. 1 shows a top view of a simplified audio system with a dipole loudspeaker suspended in a hypothetical acoustic transparent headrest according to a first model;
[0051] FIG. 2 shows a top view of the audio system of FIG. 1, depicting a headrest having a more realistic acoustic characteristic according to a second model;
[0052] FIG. 3 shows a top view of an audio system according to a first embodiment;
[0053] FIG. 4 plots the SPL against distance from the resonating surface for the first model and the exemplary embodiment;
[0054] FIG. 5 shows a top view of an audio system according to a second embodiment;
[0055] FIG. 6 shows front views of the audio system of the second embodiment;
[0056] FIG. 7 shows front and top views of the audio system of the second embodiment including a depiction of a listener’s position;
[0057] FIGS. 8a and 8b plots the force acting on the headrest and diaphragm over the frequency range and for an upright seat angle and a reclined seat angle;
[0058] FIG. 9a depicts the design options of the progressivity of the secondary suspension system and FIG. 9b shows a graph depicting the static deflection of the secondary suspension system at varying angles of headrest recline;
[0059] FIG. 10 FIG. 10 depicts options for controlling the stiffness and progressivity of the attachment formations;
[0060] FIG. 11 shows a top view of an audio system according to a third embodiment;
[0061] FIG. 12 shows a top view of an audio system according to a fourth embodiment;
[0062] FIG. 13 shows FIGS. a-l depicting top views of alternative designs of an audio system;
[0063] FIG. 14 shows a top view of an alternative design of an audio system;
[0064] FIG. 15 shows a front view of variations a-d of the audio system; and
[0065] FIG. 16 shows a pictorial view of an assembly process of assembling an audio system.
DETAILED DESCRIPTION OF THE INVENTION
[0066] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.
[0067] Referring to FIG. 1 there is shown an audio system 1 comprising a dipole loudspeaker 100 mounted in a headrest 200. The dipole loudspeaker 100 comprises a diaphragm 110 having a first radiating surface 112 and a second radiating surface 114. The first surface 112 is shown as a front surface, which faces towards a passenger seated in a seat that incorporates the headrest, and the second surface 114 is shown as the opposed rea surface, which faces away from a passenger seated in a seat that incorporates the headrest. Suitably, the diaphragm is made of extruded polystyrene foam or similar and may optionally be reinforced with a surface skin. The diaphragm 110 is suspended from a frame 120 by a primary suspension system 130. The dipole loudspeaker 100 also includes a drive unit 140 configured to drive the diaphragm 110 to produce bass frequencies as is known in the art. Consequently, in operation, the dipole speaker 100 is operational to drive the first radiating surface 112 to emit a sound in bass frequencies and the second surface 114 to emit a response 180 degrees out of phase. This out of phase response is an anti-phase sound and interferes with the sound from the first surface to act to cancel out the sound. The shortest path length of the sound from the first surface 112 to the second surface 114 (and vice a versa) is depicted in FIG. 1 by arrow P. The general structure and operation of the dipole speaker is explained above and in more detail in WO2019/121266, and the description of the dipole speaker therein is herein incorporated by reference.
[0068] FIG. 1 is a simplistic top view prepared for modelling purposes and to show the operation of a low frequency dipole loudspeaker 100 suspended directly from the headrest 200. Here it was identified that by directly mounting the frame 120 to the headrest via a secondary suspension system (shown in FIG. 1 as resilient spring elements 150), the second frame required by the dipole speaker of WO2019/121266 could be omitted from the audio system 1. In FIG. 1, the headrest is modelled as being hypothetically acoustically transparent. Here the shortest path length P is defined mainly by the dimensions of the dipole loudspeaker 100. The path length P is illustratively shown by circular arrow, though it will be appreciated that a more realistic presentation of the actual path would follow the contours of the vibrating surface and surrounding obstacles.
[0069] FIG. 2 depicts the same dipole loudspeaker mounted in a headrest shown as comprising a more realistic foam representation. For instance, the headrest 200 is formed from a foam structure 210 forming the main structure of the headrest to provide support to a listener, with the dipole loudspeaker 100 mounted in a cavity 212 in the foam structure. The foam structure is formed from foam selected to provide support to a listener and may have a density of around 20 Kg/m.sup.3 and 150 kg/m.sup.3 and more typically between 50 kg/m.sup.3 and 100 kg/m3. For instance the foam structure may be formed from an open cell PU foam having high flow resistance and therefor high acoustic resistance. The foam structure can be milled resulting in open surfaces, or it can be moulded resulting in a closed cell surface and very high, or infinite flow resistance. A front opening 214 to the cavity 212 and a rear opening 216 to the cavity are formed through the foam structure. The openings are acoustic openings and are shown as being filled with acoustically transparent foam. For instance, the headrest 200 is formed from a main body assembly 202 comprising the foam structure 210 and pieces of acoustically transparent foam 230. Here the acoustically transparent foam is shown as piece 232 and 234 configured to substantially close the openings 214, 216. Although the openings 212, 214 may be structurally closed, they remain acoustically open, that is open for sound propagation there through. The acoustically transparent foam 230 may be an open cell foam selected for acoustic transparency wherein the material is chosen to have a very low flow resistance. For instance suitably the acoustically transparent foam 230 may be a material with a specific airflow resistance (Rs) lower than 20 Pa.s/m and more preferably lower than 10 Pa.s/m.
[0070] It has been found that the resulting path length P of the FIG. 2 model is shortened compared to the acoustically transparent modelled headrest shown in FIG. 1. It is thought the presence of the foam structure acts to guide the sound and shorten the path length. That is, by enclosing the path length and allowing the path length to be guided inside the cavity the path length P is shortened, which reduces the effective output of the audio system 1 through a partial enhanced acoustic short circuit.
[0071] According to one exemplary embodiment, FIG. 3 depicts the same dipole speaker 100 used to model FIGS. 1 and 2 and mounted in an exemplary headrest 200. Here, the headrest 100 has been adapted to mount the frame 120 directly to the headrest 200 via a projecting element 220. The projecting element 220 extends from an inside wall of the cavity 212 of the headrest. As explained herein, the projecting element 220 can take a number of forms, but is shown in FIG. 3 as a first projection 221 and a second projection 222 that extend around the periphery of the frame. Also explained further herein, the frame can be connected to the projecting element in a number of ways, but is shown in FIG. 3 as being fixed with glue or the like.
[0072] It has been found that by arranging the projecting element 220 to extend between the headrest foam structure, which is acoustically resistive, and the frame 220 of the dipole loudspeaker, in a manner to substantially close a first or front side of the cavity 212 from a second or back side of the cavity 212, the front radiating surface of the dipole loud speaker can be acoustically isolated from the back radiating surface. Conveniently, the projecting elements can be formed integrally from the structural foam and is therefore acoustically resistive, and also provides a convenient manufacturing process for the projecting element 220 without an additional process or particular additional cost. Here, the projecting element 220 acts as a waveguide formation to guide sound. Thus, the projecting element 220 acts as a waveguide formation to guide sound propagating from the first or front resonating surface out of the first or front opening 214. The projecting element 220 also acts as a waveguide formation to guide sound propagating from the second or back resonating surface out of the second or back opening 216. In acting as a waveguide formation, the projecting element 220 guides the path length externally to the headrest as shown by arrow P. Advantageously, by guiding the path length externally to the headrest, an acoustic short circuit within the headrest is prevented and a larger acoustic path length is obtained as compared to the arrangements shown in both FIG. 1 and FIG. 2. As mentioned above, the headrest foam and the projecting elements, for instance the attachment formation and the waveguide formation, are acoustically resistive. Suitably, the material is a suitable foam, and in particular a foam or other material having a Specific Airflow Resistance (Rs) higher than 30 Pa.s/m or more preferred higher than 60 Pa.s/m.
[0073] Here, FIG. 4 plots the Sound Pressure Level (SPL) at distances from the first resonating surface of the diaphragm for a frequency of 60 Hz. The diaphragm makes an excursion of 5 mm peak. The solid line Sd50P5 plots the expected results for the arrangement of the audio system shown in FIG. 1 wherein the headrest is modelled as acoustically transparent. The dotted line Sp50P10 plots the expected results for the arrangement shown in FIG. 3 using the exemplary headrest including the projecting element 220 acting as a waveguide formation to guide the path length P externally to the headrest and, in the modelled embodiments, extend the path length P from 5 cm to 10 cm compared to the FIG. 1 model. The SPL v distance from the diaphragm of the FIG. 2 embodiment has not been modelled, but because the path length is shorter than the path length of FIG. 1, it is believed if FIG. 2 was plotted on the graph shown in FIG. 4, the line would be beneath the solid line for the FIG. 1 model. It will be appreciated that the graph of FIG. 4 illustrates that by increasing the path length P, the SPL at a given distance is increased for the exemplary headrest incorporating waveguide formations to guide the sound from the same dipole loudspeaker 100 and extend the path length to be external to the headrest. Suitably, in the exemplary embodiment wherein the waveguide structure extends the path length externally to the headrest 200, a resulting path length is preferably arranged to be between 5 cm and 20 cm, more preferably between 7.5 cm and 15 cm.
[0074] Referring back to FIG. 3, the projecting element 220 also provides the function of the secondary suspension system. Here, the projecting elements provide attachment formations for attaching the dipole loudspeaker to the headrest and specifically, the structural foam 210 directly to the frame 120. That is, the projecting elements are provided with a resiliency and a stiffness characteristic optimised for the secondary suspension system. Advantageously, by forming the secondary suspension system from projecting element 220, which is formed integrally to the structural foam 210, the secondary suspension system can be formed conveniently. Further explanation of the projecting element 220 forming the secondary suspension system will be described below.
[0075] In FIG. 3, the exemplary headrest is shown with the projecting element 220 combining the function of the waveguide formation with the function of the attachment formation. However, in some embodiments, the functions are separated and the projecting element 220 only provides one of the functions, with the other function provide by a separate element.
[0076] A second exemplary embodiment of an audio system 1 is shown in FIG. 5. The dipole loudspeaker 100 is shown as having a different construction to the dipole loudspeaker 100 of the previous embodiment. However, the main components and function remain of a diaphragm 110 suspended from a frame 120 by a primary suspension system 130 and including a drive unit 140 for driving the diaphragm to vibrate at bass frequencies. In FIG. 5, the dipole loudspeaker 100 has been adapted to include a corresponding attachment formation 160. The attachment formation 160 connects to the attachment formation of the headrest to fix the frame 120 to the headrest 200. The corresponding attachment formation is shown as an open cavity defined by parallel fins 161, 162. The fins 161, 162 receive the attachment formation of the headrest. As shown, suitably the attachment formation is a bulbous head 222 of the projecting element 220. The bulbous head may be oversized relative to the open cavity between fins 161, 162 such that the corresponding attachment formation is pushed on to the attachment formation of the headrest, with the bulbous head compressing between the fins. Alternatively, the bulbous head 222 may be correspondingly sized or marginally undersized to push fit therein.
[0077] In the embodiment shown in FIG. 5, the projecting element 220 extends from the structural foam 210 and from around the middle of the cavity 212 formed therein. A rear opening 216 is formed as well as a front opening 214. Here, the front opening 212 has been divided in to first and second apertures by a central piece 218 of the foam structure. The central piece 218 of the foam structure is provided to support the listeners head 2 (see FIG. 7) as the acoustically transparent foam may be too soft to provide adequate support to the user. Again, the headrest is formed from a main body assembly 202 comprising the foam structure 210 and acoustically transparent material 230. The acoustically transparent material 230 is shown as rear piece 232 and first and second front pieces 235, 236.
[0078] The headrest 200 is formed from a main body assembly 202 including the foam structure 210 and the acoustically transparent filler pieces 230. The acoustically transparent pieces maintain the acoustic openings 214, 216 but physically close the main body assembly 202 to enclose the cavity 212 in which the dipole loudspeaker 100 is mounted. The main body assembly 202 of the headrest 200 also includes a chassis frame 204 that is provided to give structural and safety features to the headrest as is known in the field of headrest design. The chassis frame may include a cage portion around the dipole loudspeaker to provide a safety aspect to resist movement of the dipole speaker out of the headrest in an impact. The chassis frame also provides attachment locations for sticks 205 (see FIG. 6) for connecting the headrest to a seat back as is known.
[0079] Although the present application is primarily concerned with providing a dipole loud speaker for producing bass frequencies, it will be understood that the audio system will also include directional speakers for the mid to high frequencies. Mid-high frequency speakers 206 are shown in FIG. 5 as being attached to the chassis frame 204 at sides of the headrest to direct sound to a personal sound cocoon in which the listener’s head is arranged to be located. It will be understood, as shown, that the acoustically transparent front pieces 235, 236, are extended to provide an opening between the mid-high frequency speakers 206 and the front of the headrest. Referring to FIG. 6, the main body assembly is shown from the front with the acoustically transparent front pieces assembled into the foam structure 210 before and after an acoustically transparent finishing material 207 is applied. The finishing material has a low flow resistance and may be a low flow resistance textile or perforated leather. FIG. 7 shows a user 2 positioned in an intended position relative to the headrest 200. Here the audio system 1 provides a personal sound cocoon around the user with a good (high) SPL within the personal sound cocoon and a good (low) SPL outside thereof.
[0080] Referring back to FIG. 5, in the second embodiment, the projecting element 220 provides both the waveguide formation function and the attachment formation function. For instance, the projecting element 220 acts with the frame 120 to provide a baffle that isolates the front and back of the cavity. Also, the projecting element 220 includes the bulbous head 222 and together forms an attachment formation that attaches the dipole loudspeaker to the headrest and provides the secondary suspension system. Here, a resilient portion 224 between the sides of the cavity and the bulbous head can be tuned to provide the required stiffness. For instance a corrugation is shown and the corrugation size can be adapted to provide a required stiffness to the resilient portion 224
[0081] Various methods of controlling the stiffness of the projecting element 220 to match a required stiffness will be discussed below. The optimum stiffness can be calculated using dynamic and static tuning calculation as is known. For instance, by plotting the force applied to the headrest from the operating dipole loudspeaker and the force applied to the diaphragm, the stiffness of the secondary suspension can be optimised. Here, referring to FIG. 8, the solid plot line represents the force acting on the headrest and that can create undesirable vibrations through the headrest if too elevated, and the dotted line represents the force acting on the diaphragm, which produces the SPL. Here, in the operating frequency range of the dipole loudspeaker (typically in the range of 40 Hz to 200 Hz), the secondary suspension system stiffness can be optimised to reduce the force to the headrest. For seats that recline, the optimisation is required to take into account the change in suspension system created by a change in angle (relative to vertical). In FIG. 8, FIG. 8a shows the seat in an upright (vertical) orientation and FIG. 8b shows the change in force created across the frequency range created by the change in stiffness of the secondary suspension system due to the change in angle (plotted for an angle of 45° to the vertical. In FIG. 8, Mms is the moving diaphragm mass, BI is the force generated by the dipole speaker drive unit, Kms is the combined stiffness of the diaphragm suspension to the frame of the dipole loud speaker, MI is the mass of the loudspeaker frame and driver, and Ks2 is the stiffness of the secondary suspension system.
[0082] In order to optimise the stiffness of the secondary suspension system across a range of recline angles, the progressivity of the secondary suspension system can also be optimised. FIG. 9 shows an optimised profile of force against deflection. The first and second suspension regions will be defined by the vibration requirements during audio playback taking in to account the mass of the dipole loudspeaker together with the second suspension tuning frequency. The maximum seat angle and second suspension tuning frequency will define its static deflection. For instance, referring to FIG. 9b, a graph showing the static deflection of the second suspension system at varying angles of seat inclination is shown. From this graph it can be seen that the preferred tuning frequency of the second suspension is between 10 Hz and 20 Hz. Below 10 Hz the static deflection of the second suspension when the seat is reclined becomes quickly excessive. And above 20 Hz the vibration transmitted to the seat will quickly become excessive as can be seen from FIG. 8b. In FIG. 8b the tuning frequency of the second suspension has risen to 20 Hz due to a very progressive second suspension. It is therefore recommended to foresee a substantially linear first suspension region so that the static deflection that occurs when reclining the seat will have less effect on the tuning frequency of the second suspension and thus better capable of maintaining a good vibration reduction to the seat. The expected mechanical impact from external vibrations will preferably be used to define the progressivity and limiting region of the suspension.
[0083] As described herein, the projecting element 220 can be tuned by controlling the stiffness in a number of ways. For instance, by changing the size of the projecting element. As shown in FIG. 10, a foam projecting element is shown in FIG. 10a. Here, the stiffness can be controlled by altering the free length X, the thickness, the density of the foam, or the inserted length Y (the inserted length Y being the length of the projecting element inserted into the corresponding attachment formation of the frame. In addition, the projecting element can be combined with other elements. For instance, in addition to or alternatively to the foam projecting element, the secondary suspension system may include a corrugated material as shown in FIG. 10b or a monolithic strip or sheet as shown in FIG. 10c. In relation to the corrugated material, the stiffness can also be controlled by the corrugation material, corrugation material thickness or size, and the corrugation pattern. In the monolithic strip or sheet, the stiffness can be controlled by the material, or the material thickness and size. Where the foam projection element 220 includes an additional element, the foam may be moulded or formed around the additional element.
[0084] Further exemplary embodiments will now be described. The further exemplary embodiments describe alternative configurations of the waveguide formation and the attachment formation and the structure of the dipole loudspeaker 100 and general configuration of the headrest 200 is not described in detail.
[0085] FIG. 11 shows a third embodiment of an exemplary audio system 1. The dipole loudspeaker 100 is mechanically attached to the headrest. The mechanical attachment is shown as a screw, but may take other forms such as a nut and bolt or the like. The attachment formation on the headrest is shown as a projecting element 220 including an inserted component 260 (or insert) moulded therein. The projecting element 220 is formed by creating slots in the sides of the cavity in the headrest. It will be appreciated that the size of the slots can be controlled to control the stiffness of the foam projecting element. Here, the cavity is formed as an aperture through the headrest from the front to the back, the aperture forming the cavity and front and back opening. The insert 260 extends form the projecting element 220 to provide a fixing location (e.g. an aperture or thread, or screwing portion) for receiving the mechanical fixing. The projecting element in combination with the insert 260 provides the secondary suspension system. The corresponding attachment formation on the frame 110 is shown as a flange that extends around the periphery of the frame, but may also be intermittent, such as tabs at the fixing locations. Multiple fixing locations may be required as is appropriate for the suspension of the frame.
[0086] In FIG. 11, the waveguide formation function is provided by the combination of the frame and projecting element 220.
[0087] FIG. 12 shows a further embodiment, wherein the audio system 1 includes a first dipole loudspeaker 100 and also a second dipole loudspeaker 100a. The second dipole loudspeaker 100a is substantially the same as the dipole loudspeaker 100 as herein described. Moreover, the headrest provides first and second cavities as herein described for mounting the first and second dipole loudspeakers. Each cavity include projecting elements 220 that provide the waveguide formation and the attachment formation. Here, the attachment formation is shown as a flange 263 on the frame. The flange 263 is inserted into an open cavity formed in a distal end of the projecting element 220. The flange 263 may be retained in the cavity by adhesive or may be retained by the length of the inserted distance of the flange. For instance, the projecting element may be compressed or deformed to push the flange into the cavity thereby eliminating the need for a further fixing. Also the stiffness of the projecting element 220 is controlled by a combination of parallel slots extending out from the projecting element. In FIG. 12, the waveguide formation is provided by the projecting element 220. The projecting element 220 in combination with the frame 110 combine to provide a sound baffle to guide the sound.
[0088] FIG. 13a shows the projecting element 220 formed by two projections 226, 228. The projections 226, 228 combine to form a partially enclosed cavity in which a corresponding attachment formation on the frame is inserted to mount the dipole loudspeaker in the headrest. Here, the corresponding attachment formation is shown as a profiled plate forming a projecting part 170. The projecting part is pushed into the partially enclosed cavity between the projections 226, 228. In this instance, the projections 226, 228 is designed to deflect to open the cavity to allow the projecting part 170 to enter. The attachment formation provides a snap fit as the projections 226, 228 spring back and close around the projecting part 170. In addition, the stiffness of the projecting element 220 is controlled by incorporating cavities 262 into the structural foam of the headrest. At the front side, the projection 228 provides the waveguide formation. Here, surfaces of the projection are curved to provide a smooth waveguide. In the back side, the projection 226 forms the waveguide formation. Here, the waveguide formation combines with the frame (and specifically, the profiled plate 170) to form a baffle.
[0089] FIG. 13b shows the projecting element 220 formed from first and second projections 226, 228. The projections are spaced a distance apart so as to increase stability of the movement. The projections 226, 228 form the attachment formation. Here, distal ends of the projections are adapted to be inserted into open cavities formed in the frame of the dipole loudspeaker 100. Here, the corresponding attachment formation on the loudspeaker 100 comprises a pair of first and second parallel flanges wherein an open cavity is formed between the first and second flanges. The foam projections 226, 228 can be pushed into the open cavities. For instance, the foam projections deflect or deform to spring into the open cavity. The dipole loudspeaker is secured to the projections by the inserted length. Projection 226 and projection 228 form the waveguide formation respectively to the rear side and the front side of the cavity formed through the headrest and in which the dipole loudspeaker is mounted. FIG. 13e shows a similar embodiment including the chassis and acoustically transparent inserts 232, 234.
[0090] Referring to FIG. 13c, the projecting element 220 forms an attachment formation similar to that of FIG. 11. However, a further foam support is provided as columns 264, 265 provided at the front and / or the back of the frame. Here, the frame is extended towards the front and back of the headrest and supported by the columns. The columns provide further suspension to assist in designing the suspension characteristics of the secondary suspension system. Moreover, the columns provide some resistance to movement of the dipole speaker in a crash situation. The projecting element 220 combines with the frame of the loudspeaker to provide a sound baffle to guide the sound from the respective vibrating surfaces and out of the front and back apertures.
[0091] In FIG. 13d, cavities and slots are used to define the stiffness of the projecting element 220. As shown, the corresponding attachment formation on the frame and the attachment formation on the headrest is formed by a profiled plate and pair of projections similar to the attachment formation of FIG. 13a. However, the profiled plate is extended at the front and back sides to extend and cover the projecting element 220. The extensions to the profiled plate are curved to provide a smooth waveguide an acoustic baffle is provided by a combination of the projecting element and the frame.
[0092] FIG. 13f depicts the audio system 1 wherein the projecting element 220 is reinforced with an insert. The insert is shown as a corrugated insert 260. The corrugated insert can be used to tune the stiffness of the projecting element 220.
[0093] FIG. 13g shows an example wherein the waveguide formation is provided by a separate component than that which provides the waveguide formation. Here, the dipole loudspeaker is attached to the headrest by a suspension element 268, shown as a monolithic sheet. The suspension 268 is separate to the foam projection element 220 and is attached to the chassis 204. Foam projections 226, 228 extend to proximity to the dipole loudspeaker to provide the waveguide formation function.
[0094] FIG. 13h provides a further example of using inserts 260 into the foam structure 210 to control the stiffness of the projecting foam element 220. The inserts 260 can be attached to the chassis or floating within the encapsulating foam.
[0095] FIG. 13I shows an example of using cavities to adapt the density of the foam and therefore the tuning frequency of the secondary suspension system. For instance, circular cavities are provided in the foam structure around the attachment formation to which the dipole loudspeaker is attached. The dipole loudspeaker 100 is further adapted to include a flexible attachment between the frame and an inner frame. Here, the diaphragm is attached to the inner frame by the first suspension system and the frame is attached to the headrest as herein described. The flexible attachment, shown as a third suspension system 131, suspends the inner frame from the frame. Providing a third (or further) suspension system can be useful to increase the design options for vibration reduction towards the seat.
[0096] In FIG. 13j, the attachment portion is shown as the foam projecting element 220, wherein the foam structure 210 is formed in two parts that are fixed or glued together after the dipole speaker has been assembled. The two part each include a portion of the projecting element so that the projecting element can sandwich a flange on the frame of the dipole loudspeaker when assembled.
[0097] FIG. 13k shows an example wherein the projecting element forming the waveguide formation is arranged to extend in front of one or both of the radiating surfaces. For instance, the foam projecting element 220 is arranged to provide an opening to the front or back opening that is more restricted than the area of the resonating surface. Thus, an overlap portion 269 is formed in between the resonating surface and the respective front or back opening.
[0098] FIG. 13I depicts an embodiment wherein the foam structure 210 has a graded or variable density profile (indicated by the change in grey-scale). For instance, the material forming the foam structure is created to have a variable stiffness by changing the density of the material at specific portions. For instance the distal ends of the projecting elements (shown a spaced first and second projections) may have a different density to the foam structure 210 spaced from the projections.
[0099] FIG. 14 shows a further implementation of an audio system according to a further exemplary embodiment. In this exemplary embodiment the waveguide formation is formed from the chassis frame 204 of the headrest. The chassis frame 204 is rigid as it provides the structure to the headrest. As shown, a distal end of the chassis frame extends into the cavity in which the speaker is located. For instance, the distal end extends partially across the cavity to restrict the cavities size between the front and back. The distal end is shown as extending substantially orthogonal to the front to back direction of the headrest. It is envisaged that the distal end of the chassis could be a continuous flange or could be a discontinuous flange as herein described. Here, the waveguide formation includes a flexible member 205 connecting the chassis to the frame of the speaker. In this way, the flexible member 205 provides the second suspension system. In addition, the frame of the speaker extends to overlap the chassis frame 204 in a direction of the headrest (i.e. the front direction of the headrest). Here, the chassis frame provides a mechanical abutment against which the speaker would impact in the event the speaker was urged to move forward through the headrest. For instance, in the example of a vehicle, in the event of a crash, the momentum of the speaker may cause the speaker to be forced forwardly and the abutment between the speaker frame and chassis frame would provide a substantial restriction to prevent the speaker from being ejected from the headrest.
[0100] Also, as shown in FIG. 14, whilst the flexible member 205 may be integral to the headrest foam as previously described, the flexible member is suitably shown as a foam element, for instance a separate foam strip. Whilst the foam strip maybe one or more separate strips, the foam strip may also be formed in a continuous manner to extend around the periphery of the cavity as explained herein in relation to examples with integral foam. The foam strip can be glued or adhered to one side of the speaker or the headrest. For instance, in FIG. 14, the foam strip is shown as being glued or adhered to the chassis frame. A further adhesive can be activated to adhere the other side of the speaker 100 or the headrest 200 thereto. For instance, as shown in FIG. 14, a further adhesive, such as an adhesive strip, may be applied to the other side of the foam strip and the speaker frame can be pushed into contact with the adhesive to secure the speaker to the foam strip. With the speaker frame and chassis frame overlapping in a forward direction, the rigid frame provide convenient elements to press together to activate the adhesive or glue during the assembly process.
[0101] In FIG. 14, the distal end of the chassis frame is bent from a portion of the chassis frame that forms an internal surface of the cavity. Here, the chassis frame provides a substantial part of the waveguide formation. The flexible member 205 also assist in the formation of the waveguide formation. It is also envisaged that where the distal end of the chassis frame extends from headrest foam, the headrest foam may also form part of the waveguide formation as herein described.
[0102] Referring to FIG. 15, the headrest is shown from the front to depict different options for the arrangement of the attachment formation and the corresponding attachment formation of dipole loudspeaker. For instance each attachment formation extends about a periphery of the frame and cavity. However, the attachment formations may extend substantially continuously about the periphery, or alternatively may extend intermittently. As shown in FIG. 14b, both the attachment formation and the corresponding attachment formation extend continuously. In FIG. 14a, the foam projecting element 220 forming the attachment formation is continuous, whereas the corresponding attachment formation on the dipole speaker is discontinuous. FIG. 14c shows the opposite arrangement wherein the foam projections are discontinuous and the corresponding attachment feature on the dipole loudspeaker is continuous. FIG. 14d depicts a possible arrangement of the additional inserted components 260 extending radially from an approximate centre of the dipole loudspeaker. The additional components are arranged at an equal spacing around the dipole loudspeaker 100.
[0103] Various aspects of the embodiments can be assembled through various assembly methods. But by way of example and referring to FIG. 16, the dipole loudspeaker 100 is pushed into the headrest 200. The dipole loudspeaker is shown as being pushed through the back opening 216, but this is not limiting and it can also be pushed through the front opening 214. The attachment formation is caused to engage or cooperate with the attachment formation on the headrest, for instance by pushing a projection on one of the parts (shown as a projection formed by a profiled plate on the frame of the dipole loudspeaker) in to a cavity on the other part (shown as a partially enclosed cavity formed between two foam projections on the foam structure 210). In one embodiment, the projections deform or deflect when the dipole loudspeaker 100 is pushed into the headrest 200. The projections spring back once the projection is inserted to snap fit the dipole speaker into the headrest. Once the dipole loudspeaker is installed in the foam structure 210, further components of the main body assembly can be installed such as the acoustically transparent infill pieces 232, 234. Some of further components of the headrest may be installed prior to assembling the dipole loudspeaker, for instance the chassis and other inserts and or any other audible components.
[0104] The audio system 1 herein described provides a dipole loudspeaker for creating bass frequencies in a personal sound cocoon around the headrest. Advantageously, the path length of the dipole loudspeaker between the two vibrating surfaces can be extended to increase the SPL within the personal sound cocoon. Furthermore, by incorporating the function of the secondary suspension system into foam projections, the audio system can be assembled with fewer parts without necessarily noticeably increasing the number or cost of the components of the headrest. The audio system 1 can be incorporated into a seat and in turn the seat in to a vehicle or the like.
[0105] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.
[0106] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.
[0107] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.
[0108] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.
[0109] Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
[0110] It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example 10%.
