Patent ID: 7388487

Claim:
A method for detecting a breaking event of a contact-sensitive surface, comprising: (a) providing an acoustic transducer and a support for the transducer; (b) providing a detector circuit responsive to the transducer for detecting an acoustic wave resulting from a contact force applied to the surface and generating a signal representing said acoustic wave, said signal having a plurality of consecutive amplitude peaks of the same or opposite phases including first and second sequential amplitude peaks; (c) scaling the amplitude of the first amplitude peak by a scaling factor less than one to establish a threshold level; (d) comparing the amplitude of the second amplitude peak to the threshold level; (e) disqualifying the contact force as a breakage event if the amplitude of the second amplitude peak is greater than the threshold level and the second amplitude peak occurs within a time window initiated by detection of the contact force; and (f) disqualifying a contact force to said support as a breakage event that relies on differentiation of the speed with which a shock wave travels through a solid material versus the speed with which an acoustic wave travels through air.