A voice prosthesis was developed that allows verbal communication of laryngectomised patients. The prosthesis requires a superiorly directed tracheoesophageal puncture in which the periscope mounted on the tracheal stoma vent is introduced. The prosthesis is operated by air injection through the periscope. Air injection is achieved by pulmonary pressure after the occlusion of the stoma vent. Stoma vent occlusion can be achieved either by the patient's finger or by the designed cover valve mounted on the prosthesis. The cover valve allows free breathing, hand-free prosthesis use, and it can release excess pressure during coughing. Periscope valve air resistance tests have been performed. The side valve used in the designed voice prosthesis demonstrates lower resistance compared to the duckbill valve in both bench and in vivo tests within the range of flows required for ordinary speech. In addition, tests have been developed that allow objective in vivo resistance measurement for other types of voice prosthesis.