Membrane tension measuring apparatus

A membrane tension measuring apparatus comprising:

• a rectangular frame adapted to be abuttable on a surface of a membrane to which tension is applied;
• an acoustic wave generator operable to emit an acoustic wave toward a part of the membrane surrounded by the frame;
• a vibration detector operable to detect vibration which is induced in the part of the membrane by the emitted acoustic wave;
• and
• a processor operable to calculate the tension based on vibration data detected by the vibration detector,
• wherein each of the acoustic wave generator, the vibration detector and the processor is mounted to the frame, and
• wherein the acoustic wave generator is a flat-panel speaker having a flat panel which is operable to emit the acoustic wave in accordance with an electrical signal, while being provided to be parallel to the part of the membrane.