Two simple experiments using FFT with digital devices in the introductory physics laboratory

We propose two experiments suited for high school and/or undergraduate physics laboratory which are aimed to the discovery of the practical meaning and usefulness of the FFT analysis as a mathematical and graphical instrument, intended to discriminate different periodic signals in various situations, ranging from basic, demonstrative measurements to very complex, real-research experiments. In our proposal, quite inexpensive digital instruments can be used, yet with accurate out-of-the-box results.