Patent EA-003215-B1 (EA)
Title: Acoustic device
Inventor: AZIMA HENRY
IPC: H04R7/22
Filed: 1999-03-30
Abstract: 1. Acoustic device relying on bending wave action and capable of operating below coincidence, comprising a member affording said acoustic operation, characterised by means at least partially bounding the member, the means having a substantially restraining nature in relation to bending wave vibration of the member, the bounding cleans being at a peripheral edge of the paid member and being peripherally continuous over up to at least 25% of said edge. 2. Active acoustic device according to claim 1, wherein comprising a bending wave transducer mounted on the panel member for excitation resonance in the panel member to generate an acoustic response. 3. Acoustic device according to claim 1 or claim 2, wherein the bounding means determines the acoustically active area within the panel member. 4. Acoustic device according to any preceding claim, wherein the acoustically active area is substantially rectangular. 5. Acoustic device according to claim 4, wherein the bounding means extends along one side of the acoustically active area. 6. Acoustic device according to claim 4 or claim 5, wherein the bounding means also extends along opposite parallel side of said acoustically active area. 7. Acoustic device according to an preceding claim, wherein the bounding means extends along each edge of the acoustically active area. 8. Acoustic device according to claim 7, wherein bending stiffness of the panel member in said acoustically active area is below about 5 Newtonmetres. 9. Acoustic device according to claim 8, wherein said bending stiffness is above about 0.001 Newtonmetre. 10. Acoustic device according to claim 7 to 9, wherein surface density of the acoustically active area is from about 25 gram/square metre. 11. Acoustic device according to any preceding claim, wherein said area of said member has isotropic bending stiffness. 12. Acoustic device according to any one of claims 1 to 10, wherein said area of said members has bidirectional anisotropy of bending stiffness. 13. Acoustic device according to any one of claims 2 to 10, wherein said area of said member has distribution of bending stiffness suiting desired beneficial location for transducer means. 14. Acoustic device according to any one of claims 1 to 11, wherein said area is substantially rectangular with isotropy of bending stiffness thereof, and has an aspect ratio between 1:1 and 1:1.5. 15. Acoustic device according to any one of claims 1 to 11, wherein said area is substantially rectangular with isotropy of bending stiffness thereof, and has an aspect ratio greater than 1:1.5. 16. Acoustic device according to any one of claims 1 to 11, wherein the acoustically active area is substantially rectangular with isotropy of bending stiffness thereof, wherein said aspect ratio is about 1:3 or more. 17. Acoustic device according to any preceding claim, wherein the panel member is tensioned. 18. Acoustic device according to claim 17, wherein the panelmember is tensioned in two mutually transverse directions. 19. Acoustic device according to claim 18, wherein the tensioning in the two directions is equal. 20. Acoustic device according to any preceding claim, wherein the bounding means is integral with the panel member. 21. Acoustic device according to claim 20, wherein the bounding means is moulded integrally with the panel member.