System and methods for characterizing and/or detecting structural characteristics of syringes (e.g., bare syringes or syringes included in automatic injection devices) using acoustic vibrations. A transducer is positioned proximate to a syringe so that the transducer vibrates at one or more frequencies and a response of the syringe to the vibrations can be received via the receiver. The response of syringe can be processed to determine a structural characteristic of the syringe.