Apparatus and method

1. An apparatus comprising:

a loudspeaker configured to convert an electrical input signal into an acoustic output signal; and

a carbon nanohorn mixture, wherein the carbon nanohorn mixture comprises carbon nanohorn material mixed with another material, wherein the carbon nanohorn mixture is positioned so as to be exposed to the acoustic output signal, wherein the carbon nanohorn mixture is bound to a substrate, and wherein the substrate comprises a carbon nanotube mat.

2. An apparatus as claimed in claim 1 wherein the carbon nanohorn material adsorbs air molecules in response to an increase in pressure caused by the acoustic output signal and so reduces the resonant frequency of the loudspeaker.

3. An apparatus as claimed in claim 1 wherein the loudspeaker is positioned within an acoustic cavity and the carbon nanohorn material is positioned within the acoustic cavity.

4. An apparatus as claimed in claim 3 wherein the acoustic cavity comprises walls configured to enable the carbon nanohorn material to be adhered to the apparatus.

5. An apparatus as claimed in claim 1 wherein the carbon nanohorn material comprises a powder.

6. An apparatus as claimed in claim 5 wherein the apparatus comprises a seal configured to prevent leakage of the carbon nanohorn material.

7. An apparatus as claimed in claim 1 wherein the carbon nanohorn material is mixed with a polymer to enable the carbon nanohorn material to be adhered to the apparatus.

8. An apparatus as claimed in claim 1 wherein the substrate is bent to enable the substrate to fit within the apparatus.

9. An apparatus as claimed in claim 1 wherein the substrate comprises paper or aluminium foil.

10. An apparatus as claimed in claim 1 wherein the carbon nanohorn mixture comprises carbon nanohorn material mixed with carbon nano-onions.

11. A method comprising:

configuring a loudspeaker to convert an electrical input signal into an acoustic output signal;

positioning a carbon nanohorn mixture so as to be exposed to the acoustic output signal, wherein the carbon nanohorn mixture comprises carbon nanohorn material mixed with another material; and

binding the carbon nanohorn mixture to a substrate, wherein the substrate comprises a carbon nanotube mat.

12. A method as claimed in claim 11 wherein the carbon nanohorn material is positioned so that the carbon nanohorn material adsorbs air molecules in response to an increase in pressure caused by the acoustic output signal and so reduces the resonant frequency of the loudspeaker.

13. A method as claimed in claim 11 comprising positioning the loudspeaker within an acoustic cavity and positioning the carbon nanohorn material within the acoustic cavity and adhering the carbon nanohorn material to walls of the acoustic cavity.

14. A method as claimed in claim 11 wherein the carbon nanohorn material comprises a powder.

15. A method as claimed in claim 14 comprising sealing the carbon nanohorn material in position to prevent leakage of the carbon nanohorn material.

16. A method as claimed in claim 11 comprising mixing the carbon nanohorn material with a polymer to enable the carbon nanohorn material to be adhered in position.

17. A method as claimed in claim 11 comprising bending the substrate to enable the substrate to fit within an apparatus.

18. A method as claimed in claim 11 wherein the substrate comprises paper or aluminium foil.