Headphone devices

Abstract: A headphone device includes a pair of housings (6) each carrying a loudspeaker unit (5), hangers (2, 3) each carrying a respective housing (6) and a headband (1) the ends of which carry the hangers (2, 3). Each housing (6) includes a front plate (12) to which the loudspeaker unit (5) is attached, and a main body (14) of the housing (6) formed of natural wood and sheathing at least the rear surface of the loudspeaker unit (5). The inner surface of the main body (14) of the housing (6) presents a number of irregularities (24).

Description: This invention relates to headphone devices. In a previously proposed headphone device to be attached to a user's head by means of a resilient headband, a loudspeaker unit is supported at each end of the headband by means of a respective housing which in turn is supported at a respective end of the headband via a loudspeaker supporting member, such as a hanger, see e.g. US-A- 3′272′926. The housing holding the loudspeaker unit is integrally moulded from synthetic resin, such as ABS or acrylic resin, into a cup-shape of substantially uniform wall thickness. The loudspeaker unit is accommodated within the housing so that the sound radiating side of the loudspeaker unit fitted with the diaphragm faces the front of the housing, that is, faces an opening formed on the side adjacent to the user's auricle, and so that the magnetic circuit on the rear side of the unit will be accommodated within the housing. In such a headphone device, the sound waves radiated from the front surface of the loudspeaker unit on driving the loudspeaker unit are radiated directly towards the user's auricle, while the sound waves radiated from the rear side of the loudspeaker unit are radiated into the inside of the housing. The housing of this headphone device is moulded from synthetic resin into the cup-shape of substantially uniform wall thickness having a smooth flat inner surface. Therefore, when the loudspeaker unit is accommodated and held within the housing with the diaphragm extending parallel to the inner surface of the housing, a standing wave is generated when the sound wave radiated from the rear side of the loudspeaker unit is reflected after impinging on the inner surface of the housing. As a result, the sound reproducing quality is lowered, and the reproduced sound heard by the user is deteriorated. Also, since the loudspeaker unit is accommodated within the housing, the vibrations of the loudspeaker unit are transmitted to the housing and excite the housing into vibration, possibly into resonance vibration at a specific frequency. In cases wherein the housing presents a smooth flat inner surface and is of a uniform plate thickness, the resonance oscillations are concentrated at one point, so that the sound pressure level at such resonant point is increased significantly, which deteriorates the reproduced sound heard by the user. Also, since the resonant oscillations are concentrated at one point of the housing, the housing itself is subjected to ringing, which further deteriorates the acoustic properties. Patent Abstracts of Japan Vol. 12 No. 69 (E-587) [2916] JP-A-62-209996 discloses a box with the entire inner face covered by projections for eliminating standing waves. Hollow rods of isosceles triangle cross section are secured by adhesive or otherwise to the inner surfaces of the box so that no opposed parallel face exists. Patent Specification US-A-3 272 926 discloses a pair of earphones provided at opposite ends of a headband, each earphone comprising an outer shell and an earcup which closes the open outer end of the outer shell. According to the present invention there is provided a headphone device comprising: a pair of housings each carrying a respective loudspeaker unit; a pair of hangers each carrying a respective one of the housings with each one of the housing including a front plate to which the respective loudspeaker unit is attached and a main body; and a headband each end of which carries a respective one of the hangers; characterized in that: the main body of each of the housing is formed of natural wood and sheaths at least the rear surface of the respective loudspeaker unit; and the inner surface of the main body presents a plurality of irregularities formed on at least the inner surface of the main body facing the rear surface of the respective loudspeaker unit and in the form of a plurality of grooves or projections. Sound waves radiated into the housing from the rear side of the loudspeaker unit on driving the loudspeaker unit are randomly reflected by the irregularities on the inner surface of the housing, so preventing generation of standing waves. These irregularities also function to scatter the resonance points on the housing caused by vibrations transmitted to the housing on driving the loudspeaker unit, and to augment the mechanical strength of the housing, as well as to prevent the occurrence of warping or deformation. The invention will now be described by way of example with reference to the accompanying drawings, throughout which like parts are referred to by like references, and in which: Figure 1 is a perspective view of an embodiment of headphone device according to the present invention; Figure 2 is an exploded perspective view showing the housing and the loudspeaker unit; Figure 3 is a longitudinal sectional view showing the housing of the headphone device; Figure 4 is a sectional view taken on line IV - IV of Figure 3; Figure 5 is a longitudinal sectional view showing a modified housing; Figure 6 is a sectional view taken on line VI - VI of Figure 5; Figure 7 is a longitudinal sectional view of another modified housing; and Figure 8 is a sectional view taken along line VIII - VIII of Figure 5. Referring to Figures 1 and 2, a headphone device includes a headband 1 formed by a resiliently deformable strap of laminated carbon fibres and hangers 2 and 3 formed of light metal such as magnesium alloy or synthetic resin. The hangers 2 and 3 are provided at respective ends of the headband 1 and form loudspeaker supporting members. Housing supporting plates 4 are pivotably supported by the hangers 2 and 3, and housings 6 containing respective left and right loudspeaker units 5 are mounted on these hangers 2 and 3 by means of the supporting plates 4. Referring to Figure 2, each housing supporting plate 4 is formed as a disc having a central opening 8 confronted by the front surface of a loudspeaker unit 5 to which is attached a diaphragm 7. The supporting plate 4 is pivotably supported by the hangers 2 or 3 by having each side carried by pivot pins 10 formed at the ends of each of the semi-arcuate hangers 2 and 3. An ear pad 11, formed of a resilient material, is bonded, such as by adhesive, to the front side of the supporting plate 4 to function as the auricular abutting portion and to ensure a comfortable feeling for the user and intimate contact with the auricle. The housing 6 is attached to the side of the supporting plate 4 opposite to the side provided with the ear pad 11. The housing 6 is made up of a front plate 12, to which the loudspeaker unit 5 is attached and held, and a main body 14 of the housing 6 contoured to sheath the rear of the loudspeaker unit 5 including a magnetic circuit 13. In this embodiment, the front plate 12 and the main body 14 of the housing 6 is formed by machining a plate-like block of unadulterated natural wood, such as from a zelkova tree, to a desired shape. The front plate 12 is mounted as one to the main body of the housing 14 by fitting an annular engaging portion 15 on the outer peripheral rim of the front plate 12 into a mating step-like annular recess 16 on the inner peripheral surface on the opening side of the main body 14 of the housing 6 and bonding them such as by adhesive. A plurality of set screws 17 secure the front plate 12 of the housing 6 to the rear of the supporting plate 4. The supporting plate 4 is formed with cut-outs 18 in which buffer elements 19 formed of, for example, rubber, are accommodated. The buffer elements 19 function to interrupt transmission of vibrations between the supporting plate 4 and the housing 6, as well as to compensate for positional deviation between the cut-outs 18 and screw holes 20 in the front plate 12 of the housing 6, to ensure positive threading engagement of the set screws 17. The loudspeaker unit 5 is attached to the housing 6, with the magnetic circuit 13 inside the housing 6, via a loudspeaker mounting aperture 21 formed at the centre of the front plate 12, until an outer peripheral rim 23 a of a flange 23 of the loudspeaker unit 5 is engaged with an engaging step 22 on the rim of the loudspeaker mounting aperture 21, the mating engaging portions then being bonded together such as by adhesive, as shown in Figure 3. On the inner side of the main body 14 of the housing 6, facing the rear of the loudspeaker unit 5 attached to the front plate 12, there are formed a plurality of inclined mutually parallel grooves 24, as shown in Figures 3 and 4. The grooves 24 are of serrated cross-sectional shape and are in the form of, as it were, wind-wrought patterns on sand, when seen in plan view. The grooves 24 are formed with an angle of inclination such that no surfaces parallel to the diaphragm 7 of the loudspeaker unit 5 are formed on the inner surface of the main body 14 of the housing 6 facing the rear of the loudspeaker unit 5. In addition, the grooves 24 are formed with a width and a pitch such that no standing wave is generated when the sound waves radiated from the rear side of the loudspeaker unit 5 are reflected from the inner surface of the main body 14 of the housing 6. A large number of sound transmitting through-holes 25 are formed in the front plate 12. The irregularities on the inner surface of the housing 6 are not limited to the juxtaposed grooves having a serrated cross-section as described above, but may also be defined by a large number of columnar projections 26 formed on the inner surface of the main body of the housing 14, as shown in Figures 5 and 6. The irregularities on the inner surface of the housing 6 may also be defined by several cross-pieces 27 projectingly formed on the inner surface of the main body 14 of the housing 6, as shown in Figures 7 and 8. Although the cross-pieces 27 are formed integrally with the main body 14 of the housing 6 in this embodiment, they could instead be in the form of separate elongated plates of reduced thicknesses which may be attached subsequently to the main body 14. Although the irregularities are shown formed only on the inner surface of the housing 6 facing the rear of the loudspeaker unit 5, they may also be provided on other inner surfaces to take account of acoustic characteristics of the device and to prevent warping or deformation of the housing 6 formed of natural wood. Absorbing materials, such as wool cotton, may be accommodated within the interior of the housing 6. The material of the housing 6 should exhibit a relatively high Young's modulus and internal loss. Although the housing 6 in the above embodiment is formed from an unadulterated block of natural wood, such as zelkova tree, it could be formed of plywood. The headphone device described has the inner surface of the housing holding the loudspeaker unit formed with the aforementioned irregularities, so that, even when the diaphragm of the loudspeaker unit is positioned parallel to the inner surface of the housing, sound waves radiated from the rear side of the loudspeaker unit are randomly reflected by the irregularities to prevent the generation of the standing wave, and to prevent the sound reproducing properties from being deteriorated. The irregularities on the inner surface of the housing also act to scatter the resonance points caused by the vibration of the housing, to prevent a ringing phenomenon of the housing itself. Moreover, since the housing is formed from a block of natural wood liable to undergo warping or deformation, the irregularities can act to prevent such warping or deformation from occurring. In this manner, it becomes possible to utilize natural wood, which is a preferred housing material because of its relatively high Young's modulus and high internal losses, with the result that a headphone device exhibiting optimum sound reproducing characteristics can be produced easily, while a headphone device formed of natural wood may be improved in durability.

Claims: A headphone device comprising: a pair of housings (6) each carrying a respective loudspeaker unit (5); a pair of hangers (2, 3) each carrying a respective one of the housings (6) with each one of the housing (6) including a front plate (12) to which the respective loudspeaker unit (5) is attached and a main body (14); and a headband (1) each end of which carries a respective one of the hangers (2, 3); characterized in that: the main body (14) of each of the housing (6) is formed of natural wood and sheaths at least the rear surface of the respective loudspeaker unit (5); and the inner surface of the main body (14) presents a plurality of irregularities formed on at least the inner surface of the main body (14) facing the rear surface of the respective loudspeaker unit (5) and in the form of a plurality of grooves (24) or projections (26, 27). A device according to claim 1, wherein the grooves (24) are inclined at a predetermined angle so as not to run parallel to the diaphragm (7) of the respective loudspeaker unit (5). A device according to claim 1, wherein the projections comprise cross-pieces (27) projectingly formed on the inner surface of the main body (14).

Inventors: DOHI MASAHIRO C O PATENTS DIVI, NAGENO KOJI C O PATENTS DIVISI, DOHI, MASAHIRO C/O PATENTS DIVISION, NAGENO, KOJI C/O PATENTS DIVISION
Applicants: SONY CORP, SONY CORPORATION
Application year: 1989
Main classification: H04R1
IPC codes: H04R1