A fuel vapor control system has a controller that carries out a leak check processing after the engine is stopped. The speakers receive audio input from a subject audio source and generate corresponding sound vibrations. Each of the Stage 1 integration circuits is configured to concurrently integrate an input signal, and to send out a Stage 1 positive signal and a Stage 1 negative signal that is reverse to the Stage 1 positive signal. The block scanning circuit sequentially selects the first to z-th blocks one by one, and alternately selects the odd-numbered line scanning circuits and the even-numbered line scanning circuits. Additionally, ridges may be formed about the periphery of each plug to facilitate its anchoring to surrounding cartilage, bone andor adjacent plugs. The prosthetic valves are particularly adapted for use in percutaneous aortic valve replacement procedures.