Ultrasound device, impedance matching layer, and electrostatic drive device

An impedance matching layer, comprising:

• a matching membrane
• having a resonance loss equal to or less than transmitted acoustic power, and
• being disposed with tension applied at a position facing a vibration surface of a vibration device;
• and
• gas sealed between the matching membrane and the vibration surface;
• wherein
• a distance between a surface of the matching membrane facing the vibration surface and the vibration surface is a value according to an amplitude amplification factor which is a ratio of an amplitude of the vibration surface to an amplitude of the matching membrane.

An electrostatic drive device, comprising:

• a first electrode that is a drive membrane and is disposed with tension applied at a position facing a second electrode;
• and
• the second electrode having a through hole, wherein
• at least one of the first electrode and the second electrode is a laminated membrane in which a plurality of materials with different conductivities are laminated,
• the laminated membrane is laminated with a first layer, a second layer, and a third layer in sequence, and the third layer is disposed at a position facing the other of the first electrode and the second electrode,
• conductivity of the second layer is less than conductivity of the first layer,
• conductivity of the third layer is equal to or less than conductivity of the first layer and greater than conductivity of the second layer, and
• the first layer and the third layer are electrically connected.