Abstract: An apparatus for sonic excitation of a surface has a housing defining an open cavity facing the surface. At least one speaker is positioned to introduce sound to the cavity. The housing comprises a gasket for sealing with the surface. A valve is coupled to the cavity to allow the cavity to be maintained at a pressure below an external pressure.

Abstract: A calibrator includes a moving element having a structural member having a mounting feature for mounting the device to be calibrated. The moving element includes first and second coils at first and second ends. A fixed element supports the moving element and includes at least one magnet magnetically cooperating with the first and second coils. In at least one mode of operation, an amplifier is coupled to the first and second coils in parallel.

Abstract: An apparatus for sonic excitation of a surface includes a transparent pane. A sidewall structure cooperates with the pane to define an open cavity facing the surface. At least one speaker is positioned to introduce sound to the cavity. Sound cancellation may be provided for at least partially canceling transmission of the sound outside the cavity.