Vibration isolation in a bone conduction device

1. A bone conduction device, comprising:

a bone fixture adapted to be fixed to bone;

a vibratory element adapted to be attached to the bone fixture and configured to vibrate in response to a sound signal, thereby producing vibrational energy; and

a vibration isolator adapted to be disposed between the vibratory element and the bone, wherein

the bone fixture has a maximum outer diameter, when measured on a first plane tangential to and on the surface of the bone at a location where the bone fixture extends into the bone, of about 1% to about 20% of the wavelength of the vibrations producing the vibrational energy.

2. The bone conduction device of claim 1 , wherein the vibratory element comprises:

an implantable plate configured to vibrate in response to vibrations generated by an external plate.

3. The bone conduction device of claim 2 , wherein:

the implantable plate comprises a magnetic plate; and

the external plate comprises a magnetic plate.

4. The bone conduction device of claim 1 , wherein the vibratory element comprises an actuator configured to generate mechanical vibrations in response to delivery of electrical signals thereto.

5. The bone conduction device of claim 4 , wherein the actuator is an electromagnetic actuator.

6. The bone conduction device of claim 4 , wherein the actuator is a piezoelectric actuator.

7. The bone conduction device of claim 1 , wherein the vibration isolator comprises a substantially planar ring disposed substantially around the outer surface of the bone fixture.

8. The bone conduction device of claim 7 , wherein the vibration isolator comprises a plurality of projections extending from the surface of the isolator abutting the skull.

9. The bone conduction device of claim 1 , wherein the vibration isolator is a coating on the surface of the vibratory element adjacent the skull.

10. The bone conduction device of claim 1 , wherein the vibration isolator is a layer attached to the surface of the vibratory element adjacent the skull.

11. The bone conduction device of claim 1 , wherein the vibration isolator is a silicon body.

12. The bone conduction device of claim 1 , wherein the bone fixture comprises a bone screw having a threaded portion and screw head, and wherein the vibration isolator has a contoured recess configured to receive the screw head therein.

13. The bone conduction device of claim 3 , wherein at least one of the implantable plate or the external plate comprises a permanent magnet.

14. The bone conduction device of claim 1 , wherein the bone conduction device is adapted for the bone fixture to extend from the vibratory element, past the vibration isolator, and into the bone.

15. The bone conduction device of claim 1 , wherein the bone conduction device is adapted for the bone fixture to extend from the vibratory element, through the vibration isolator, and into the bone.

16. The bone conduction device of claim 1 , wherein the bone fixture and vibratory element are adapted to be rigidly attached, and wherein the bone conduction device is configured to substantially vibrationally isolate the vibratory element from the bone, except for a vibrational energy path through the bone fixture.

17. The bone conduction device of claim 1 , wherein the vibratory element is larger than the bone fixture, and wherein the bone conduction device is configured to substantially limit a vibrational conductive channel from the vibratory element to the bone to a channel passing through the bone fixture.

18. A transcutaneous bone conduction device, comprising:

a bone fixture adapted to be fixed to bone; and

a vibratory element that is larger than the bone fixture and adapted to be rigidly attached to the bone fixture and configured to generate vibrational energy in response to a sound signal, wherein

substantially all of the vibrational energy transmitted to the bone is transmitted to the bone via the bone fixture, and

the bone fixture has a maximum outer diameter, when measured on a first plane tangential to and on the surface of the bone at a location where the bone fixture extends into the bone, of about 1% to about 20% of the wavelength of the vibrations producing the vibrational energy.

19. The bone conduction device of claim 18 , further comprising a vibration isolator adapted to be disposed between the vibratory element and the bone.

20. The bone conduction device of claim 19 , wherein the vibration isolator is a silicon body.

21. The bone conduction device of claim 18 , wherein:

the vibratory element includes:

a maximum outer periphery having a maximum outer peripheral diameter; and

a maximum bone contact surface area having a maximum contact surface diameter;

the vibratory element is configured to contact the bone only at the maximum bone contact surface area; and

the maximum contact surface diameter is substantially less than the maximum outer peripheral diameter.

22. The bone conduction device of claim 21 , wherein:

the maximum contact surface diameter is less than or equal to about half of the maximum outer peripheral diameter.

23. The bone conduction device of claim 21 , wherein:

the maximum contact surface diameter is less than or equal to about a quarter of the maximum outer peripheral diameter.

24. The bone conduction device of claim 18 , further comprising a vibration isolator adapted to be disposed between and against the vibratory element and the bone, wherein the vibration isolator has an outer periphery that is contoured to smoothly extend away from the surface of the bone when the vibration isolator is positioned against the surface of the bone.

25. The bone conduction device of claim 18 , wherein the vibratory element includes:

a surface configured to contact the bone, wherein the surface has a surface roughness Ra of about 0.4 micrometers or less.

26. The bone conduction device of claim 18 , wherein the vibratory element includes:

a surface configured to contact the bone, wherein the surface has a surface roughness Ra of about 0.3 micrometers or less.

27. The bone conduction device of claim 19 , wherein the bone conduction device is adapted for the bone fixture to extend from the vibratory element, past the vibration isolator, and into the bone.

28. The bone conduction device of claim 19 , wherein the bone conduction device is adapted for the bone fixture to extend from the vibratory element, through the vibration isolator, and into the bone.

29. A method of enhancing hearing of a recipient, the method comprising:

capturing a sound signal;

vibrating a vibratory element in response to the captured sound signal, thereby generating vibrational energy; and

conducting more of the vibrational energy from the vibratory element to bone of the recipient via an at least partially artificial pathway extending from the vibratory element to the bone than is otherwise conducted from the vibratory element to the bone, wherein

an artificial portion of the at least partially artificial pathway has a maximum outer diameter, when measured on a first plane tangential to and on the surface of the bone at a location where the artificial portion of the artificial pathway contacts the bone, of about 1% to about 20% of the wavelength of the vibrations generational the vibrational energy.

30. The method of claim 29 , wherein:

substantially more of the vibrational energy from the vibratory element is conducted to the bone through the at least partially artificial pathway than is otherwise conducted to the bone from the vibratory element to the bone.

31. The method of claim 29 , wherein:

substantially all of the vibrational energy from the vibratory element is conducted to the bone through the at least partially artificial pathway.

32. The method of claim 29 , wherein:

the artificial pathway includes a section having a maximum outer diameter when measured on a first plane tangential to and on a surface of the bone at the location where the at least partially artificial pathway extends to the bone, of about 1% to about 20% of the wavelength of the vibrations producing the vibrational energy.

33. The method of claim 29 , wherein:

the conducting includes attenuating some of the vibrational energy that is otherwise conducted from the vibratory element to the bone.