Bending wave acoustic radiator
A bending wave panel-form acoustic radiator formed from sheet material to define an acoustically active area and having at least one integral stiffening member in the form of a corrugation extending out of the plane of the sheet and at least partially across the acoustically active area of the radiator, which stiffening member is of substantially U-shaped cross section. Also disclosed is a method of making a bending wave panel-form acoustic radiator, comprising forming a sheet into a panel having at least one integral corrugation member extending out of the plane of the sheet and at least partly across the sheet and of substantially U-shape cross-section, to stiffen the sheet to have a desired ability to support and propagate bending waves.
1. A loudspeaker comprising a bending wave panel-form acoustic radiator and a vibration transducer coupled to the radiator, wherein the radiator is formed from material in the form of a sheet to define an acoustically active radiator area and has at least one integral stiffening member in the form of a corrugation extending out of the plane of the sheet and at least partially across the acoustically active area of the radiator so as to be exposed on at least one face of the radiator, which stiffening member is of substantially U-shaped cross section, the transducer being coupled to the acoustically active area of the radiator.
2. A loudspeaker according to claim 1 , wherein the sheet is of substantially uniform thickness over the acoustically active area within the limitations imposed by the integral forming of the stiffening member(s).
3. A loudspeaker according to claim 1 or claim 2 comprising stiffening members arranged to extend in a plurality of directions across the acoustically active area.
4. A loudspeaker according to claim 3 , wherein the stiffening members extend substantially wholly across the acoustically active area.
5. A loudspeaker according to claim 4 , wherein the acoustically active area is substantially filled with closely spaced stiffening members.
6. A loudspeaker according to claim 5 , wherein the stiffening members are rectilinear.
7. A loudspeaker according to claim 3 , wherein the stiffening members are rectilinear.
8. A loudspeaker according to claim 3 , wherein the stiffening members are disposed in a substantially radial array extending from a position on the acoustically active area at which a vibration exciter is intended to be located.
9. A loudspeaker according to claim 8 , comprising substantially planar portions of the acoustically active area of the sheet defined between the substantially radial stiffening members.
10. A loudspeaker according to claim 1 or claim 2 comprising stiffening members arranged in a parallel array.
11. A loudspeaker according to claim 10 , wherein the stiffening members extend substantially wholly across the acoustically active area.
12. A loudspeaker according to claim 11 , wherein the acoustically active area is substantially filled with closely spaced stiffening members.
13. A loudspeaker according to claim 12 , wherein the stiffening members are rectilinear.
14. A loudspeaker according to claim 10 , wherein the stiffening members are rectilinear.
15. A loudspeaker according to claim 10 , wherein the stiffening members are disposed in a substantially radial array extending from a position on the acoustically active area at which a vibration exciter is intended to be located.
16. A loudspeaker according to claim 15 , comprising substantially planar portions of the acoustically active area of the sheet defined between the substantially radial stiffening members.
17. A loudspeaker according to claim 1 or claim 2 , wherein the stiffening members are of substantially uniform cross-section over their lengths.
18. A loudspeaker according to claim 1 or claim 2 , wherein the acoustically active area is generally rectangular and wherein the stiffening members extend at an angle to the edges of the acoustically active area.
19. A loudspeaker according to claim 1 or claim 2 , wherein the stiffening members are endless.
20. A loudspeaker according to claim 1 or claim 2 , wherein the stiffening members comprise portions of their length extending in different directions.
21. A loudspeaker according to claim 1 or claim 2 , wherein the stiffening members are discrete.
22. A loudspeaker according to claim 21 , wherein the stiffening members are shaped to be rounded in cross-section so as to avoid sharp edges.
23. A loudspeaker according to claim 1 or claim 2 , wherein the sheet material is of a plastically deformable material.
24. A loudspeaker according to claim 1 or claim 2 , wherein the sheet comprises a termination area at least partially surrounding the acoustically active area.
25. A loudspeaker according to claim 1 or claim 2 , wherein the stiffening member is of substantially uniform height over its length.
26. A loudspeaker according to claim 1 or claim 2 , wherein the acoustic radiator comprises a corrugated sheet.
27. A loudspeaker according to claim 1 or claim 2 , wherein the acoustic radiator comprises a plurality of corrugated sheets.
28. A loudspeaker according to claim 27 , wherein the plurality of corrugated sheets are united face to face.
29. A loudspeaker according to claim 28 , wherein corrugations on one sheet are angled with respect to adjacent corrugations on an adjacent sheet.
30. A loudspeaker according to claim 1 , wherein the panel is a plastics thermoforming.
31. A loudspeaker according to claim 30 , wherein the vibration transducer is mounted to the side of the panel from which plastics was moved to form the stiffening member.