Acoustic transducer

An active acoustic transducer comprising:

• a) a one-piece mandrel in the form of a modified cylinder substantially symmetric about a central axis and having:
• a first mandrel region including an outer surface substantially parallel to the central axis and at a first substantially constant radial distance from the central axis, and
• a second mandrel region including an outer surface substantially parallel to the central axis and at a second substantially constant radial distance from the central axis, the second substantially constant radial distance being less than the first substantially constant radial distance,
• whereby the first region includes a shoulder member extending from the outer surface of the first region to the outer surface of the second region,
• b) an anvil in the form of a cylinder substantially symmetric about the central axis and having:
• first and second ends,
• an outer anvil surface substantially parallel to the central axis and at a third substantially constant radial distance from the central axis, and
• a central aperture bound by an inner anvil surface that is substantially parallel to the central axis, the inner anvil surface being at a fourth substantially constant radial. distance from the central axis, the fourth substantially constant radial distance being less than the third substantially constant radial distance,
• whereby the anvil includes a base member in the region of the first end extending from the outer anvil surface to the inner anvil surface,
• the anvil being positioned so that part of the second region of the mandrel passes through the central aperture bound by the inner surface of the anvil, and
• c) a plurality of washer-shaped discs comprising piezoelectric material and having an outer radius and an inner radius, the inner radius being slightly larger than the substantially constant radial distance associated with the outer surface of the second region of the mandrel, and the outer radius being larger than the inner radius,
• the plurality of discs being captured between the shoulder member of the first region of the mandrel and the base of the anvil in a pre-stressed interference fit.