In one implementation, a storage system comprises host computers, a management terminal and a storage system having block interface to communicate with the host computersclients. The transducer structure includes a flexible membrane supported between a first volume and a second volume, and at least one variable vent structure in communication with at least one of the first and second volumes. The cross-sectional area of which exit gap changes in according to the position of the piston. Upon receiving the speech command from the user that is described within the recognition grammar, a network interface system accesses the information source and retrieves the information requested by the user.