Acoustic device
Acoustic device including a member extending transversely of its thickness and capable of sustaining bending waves at least over an intendedly consequentially acoustically active area of the transverse extent of said member, the member having, by reason of orderly design methodology disclosed and claimed, a distribution of resonant modes of its natural bending wave vibration at least over said area that is dependent on values of particular parameters of said members, including geometrical configuration and directional bending stiffness(es), which values have been selected to predetermine said distribution of natural resonant modes being consonant with required achievable acoustic action of said member for operation of said device over a desired operative acoustic frequency range.
1. A method of making a resonant acoustic object adapted for operation over an operative frequency range, the object comprising a member extending transversely of its thickness and capable of sustaining bending waves over an active area of the transverse extent of the member, wherein the distribution of resonant modes of bending wave vibration over the active area of the member depends on the values of physical parameters of geometry, bending stiffness, areal mass distribution and damping of the member, the method comprising:
selecting, through analysis, values of said parameters to effect a desired distribution of the resonant bending wave modes in frequency over the active area of the member, wherein said parameters are associated with at least two different directions across the active area of the member, and the values of said parameters are selected such that the frequencies of the resonant bending wave modes along one of said different directions substantially do not overlap with the frequencies of the resonant bending wave modes along the other of said different directions; and
making the member having said selected values of said parameters.
2. A method according to claim 1 , wherein said different directions are substantially perpendicular.
3. A method according to claim 1 , wherein the values of said parameters are selected such that the frequencies of the resonant bending wave modes along said different directions are interleaved and spread so that there are substantially minimal clusterings and disparities of spacings of said frequencies.
4. A method according to claim 3 , wherein said different directions are substantially perpendicular.
5. A method according to claim 1 , wherein said parameters comprise the lengths of the major and minor axes of the member.
6. A method according to claim 5 , wherein the lengths of said major and minor axes are selected such that the frequencies of the resonant bending wave modes along one of said axes substantially do not overlap with the frequencies of the resonant bending wave modes along the other of said axes.
7. A method according to claim 6 , wherein the values of said parameters are selected such that the frequencies of the resonant bending wave modes along said axes are interleaved and spread so that there are substantially minimal clusterings and disparities of spacings of said frequencies.
8. A method of making a loudspeaker adapted for operation over an operative frequency range, the loudspeaker including a member extending transversely of its thickness and capable of sustaining bending waves over an active area of the transverse extent of the member, and a transducer coupled to the member to vibrate the member, wherein the member when vibrating has a desired frequency distribution of resonant bending wave modes over the active area of the member, the method comprising:
analysing the distribution of resonant bending wave vibration of the member, including determining at least one region of the active area of the member where a plurality of lower frequency resonant bending wave modes in the operative frequency range have vibrationally active anti-nodes; and
coupling a transducer to a said at least one region of the active area of the member so that the transducer will couple with the lower frequency resonant bending wave modes.
9. A method of making a loudspeaker adapted for operation over an operative frequency range, the loudspeaker including a member extending transversely of its thickness and capable of sustaining bending waves over an active area of the transverse extent of the member, and a transducer coupled to the member to vibrate the member, wherein the distribution of resonant modes of bending wave vibration over the active area of the member depends on the values of physical parameters of geometry, bending stiffness, areal mass distribution and damping of the member, the method comprising:
selecting, through analysis, values of said parameters to effect a desired frequency distribution of the resonant bending wave modes over the active area of the member; making the member having said selected values of said parameters;
analysing the distribution of resonant bending wave vibration of the member, including determining at least one region of the active area of the member where a plurality of lower frequency resonant bending wave modes in the operative frequency range have vibrationally active anti-nodes; and
coupling a transducer to a said at least one region of the active area of the member so that the transducer will couple with the lower frequency resonant bending wave modes.
10. A method according to claim 9 , wherein said parameters are associated with at least two different directions across the active area of the member, and the values of said parameters are selected such that the frequencies of the resonant bending wave modes along one of said different directions substantially do not overlap with the frequencies of the resonant bending wave modes along the other of said different directions.
11. A method according to claim 10 , wherein said different directions are substantially perpendicular.
12. A method according to claim 10 , wherein the values of said parameters are selected such that the frequencies of the resonant bending wave modes along said different directions are interleaved and spread so that there are substantially minimal clusterings and disparities of spacings of said frequencies.
13. A method according to claim 10 , wherein said different directions are substantially perpendicular.
14. A method according to claim 9 , wherein said parameters comprise the lengths of the major and minor axes of the member.
15. A method according to claim 14 , wherein the lengths of said major and minor axes are selected such that the frequencies of the resonant bending wave modes along one of said axes substantially do not overlap with the frequencies of the resonant bending wave modes along the other of said axes.
16. A method according to claim 15 , wherein the values of said parameters are selected such that the frequencies of the resonant bending wave modes along said axes are interleaved and spread so that there are substantially minimal clusterings and disparities of spacings of said frequencies.