US Patent 11430249 Passive acoustic fingerprint sensor

An acoustic receiver system may be configured for receiving dynamic friction acoustic waves produced via relative motion between an outer surface of an apparatus and a target object in contact with the outer surface. A control system may be configured for receiving acoustic signals from the acoustic receiver system. The acoustic signals may correspond to a first instance of the dynamic friction acoustic waves. The control system may be configured for extracting target object features from the first acoustic signals and for performing an authentication process based, at least in part, on the target object features.