This paper reviews the transmission of high frequency broadband ultrasound via a thin layer in contact with a solid. A large part of this article deals with the physics of the acoustic resonance in a material system comprising water, a thin layer and a solid. Generally, it is very difficult to maintain the continuity between the layer and the solid during transmission of the ultrasound. The dry-contact ultrasonic technique, where the air at the layer/solid interface has been evacuated, enables the transmission of high frequency broadband ultrasound via the interface and allows us to realize acoustic imaging without the sample getting wet. In this case, to realize high-resolution acoustic imaging of a solid sample, selection of the layer to be inserted is important, and the acoustic resonance phenomenon is used for this purpose. The dry-contact and conventional ultrasonic techniques and their respective inspection capabilities are compared in this article. Moreover, the acoustic resonance phenomenon is used to characterize layered media. The acoustic properties of a thin polymer film, i.e., the acoustic impedance, ultrasonic velocity and density, can be accurately determined, and any scattering sources, e.g., voids, etc., can be detected with high sensitivity using this technique. The thicknesses of coatings on both surfaces of a steel plate can also be precisely measured by observing the acoustic resonance phenomenon occurring in the ultrasonic transmission system.