Detection of type of object used to provide a touch contact input

1. A system for determining a touch contact object type, comprising:

a communication interface configured to:

send a sent signal to be used to propagate a freely propagating signal through a propagating medium with a touch input surface, wherein the freely propagating signal has been allowed to freely propagate through the propagating medium in multiple directions to a plurality of receivers on multiple axes of the propagating medium;

and receive a received signal detected due to a touch input object contacting the touch input surface, wherein the received signal includes the freely propagating signal that has been disturbed by the touch input object; and

a processor coupled with the communication interface and configured to:

compare at least a portion of the received signal with one or more signatures of one or more touch input object types, wherein comparing at least the portion of the received signal with the one or more signatures of the one or more touch input object types includes comparing a portion of the freely propagating signal that has been disturbed by the touch input object with the one or more signatures of the one or more touch input object types; and

determine a type of the touch input object contacting the surface based at least in part on the comparison.

2. The system of claim 1 , wherein the received signal was detected by a transducer.

3. The system of claim 2 , wherein the transducer is coupled to a medium of the touch input surface.

4. The system of claim 1 , wherein the determining the type of touch input object includes determining whether the touch input object type is a finger object type.

5. The system of claim 1 , wherein the determining the type of touch input object includes determining whether the touch input object type is a stylus object type.

6. The system of claim 5 , wherein if it is determined that the touch input object type is the stylus, a handwriting detection is invoked.

7. The system of claim 1 , wherein the determined type of the touch input object is used at least in part to initiate a device behavior based on the determined type.

8. The system of claim 1 , wherein the determined type is one of a plurality of determined types including a determined type for each touch contact of a multi-touch input.

9. The system of claim 1 , wherein the one or more signatures include one or more waveform signatures.

10. The system of claim 1 , wherein comparing at least the portion of the received signal with the one or more signatures includes matching in a time domain by correlating the at least a portion of the received signal with one or more waveforms of the one or more signatures.

11. The system of claim 1 , wherein comparing at least the portion of the received signal with the one or more signatures includes frequency-domain matching at least a portion of the received signal with one or more frequency-domain spectra of the one or more signatures.

12. The system of claim 1 , wherein comparing at least the portion of the received signal with the one or more signatures includes wavelet-domain matching at least a portion of the received signal with one or more wavelet-domain transforms of the one or more signatures.

13. The system of claim 1 , wherein the received signal was detected by converting a detected vibrational energy to the received signal.

14. The system of claim 1 , wherein one or more components of the system are powered down while awaiting to receive the received signal detected due to the touch input object contacting the touch input surface.

15. The system of claim 1 , wherein comparing at least the portion of the received signal with the one or more signatures includes comparing a predetermined amount of time of the received signal with the one or more signatures.

16. The system of claim 1 , wherein the processor is further configured to filter a background noise included in the received signal.

17. The system of claim 16 , wherein filtering the background noise includes measuring a rate of spectral change of at least a portion of the received signal.

18. The system of claim 17 , wherein measuring the rate of spectral change includes computing a fast Fourier transform of at least a portion of the received signal.

19. The system of claim 1 , wherein the received signal includes an acoustic signal.

20. A method for determining a touch contact object type, comprising:

sending a sent signal to be used to propagate a freely propagating signal through a propagating medium with a touch input surface, wherein the freely propagating signal has been allowed to freely propagate through the propagating medium in multiple directions to a plurality of receivers on multiple axes of the propagating medium;

receiving a received signal detected due to a touch input object contacting the touch input surface, wherein the received signal includes the freely propagating signal that has been disturbed by the touch input object;

using a processor to compare at least a portion of the received signal with one or more signatures of one or more touch input object types, wherein comparing at least the portion of the received signal with the one or more signatures of the one or more touch input object types includes comparing a portion of the freely propagating signal that has been disturbed by the touch input object with the one or more signatures of the one or more touch input object types; and

determining a type of the touch input object contacting the surface based at least in part on the comparison.

21. A computer program product for determining a touch contact object type, the computer program product being embodied in a non-transitory computer readable storage medium and comprising computer instructions for:

sending a sent signal to be used to propagate a freely propagating signal through a propagating medium with a touch input surface, wherein the freely propagating signal has been allowed to freely propagate through the propagating medium in multiple directions to a plurality of receivers on multiple axes of the propagating medium;

receiving a received signal detected due to a touch input object contacting the touch input surface, wherein the received signal includes the freely propagating signal that has been disturbed by the touch input object;

comparing at least a portion of the received signal with one or more signatures of one or more touch input object types, wherein comparing at least the portion of the received signal with the one or more signatures of the one or more touch input object types includes comparing a portion of the freely propagating signal that has been disturbed by the touch input object with the one or more signatures of the one or more touch input object types; and

determining a type of the touch input object contacting the surface based at least in part on the comparison.