FFTExplorer

FFTExplorer is a lightweight and interesting piece of software designed to help you perform real-time spectral analysis with the help of its internal synthesizer. In addition, the utility makes it possible for you to analyze spectra for various sound file types.
Provided you already have Java installed on your computer, the application requires you to go through a stress-free and common installation process. Subsequent to its installation, you can start using the application right off the bat, without requiring any special configuration processes.

Scientific tool with a user-friendly and intuitive interface

The tool enables you to choose the parameters within its Synthesizer tab, such as Time span, Vertical Gain, Frequency span, the Line Width and the display mode, as well as the display modes namely Time, Frequency, Horizontal and Antialias.
It is the exact same story when it comes to is external sources, with the only difference being that you can choose the data rate for your sound card source and the audio file source's location.

A few simple clicks and this app displays animated real-time graphs

Plainly speaking, according to your added values, FFTExplorer basically displays animated frequency-domain and time-domain graphs with a single click on the “Start” button. Furthermore, the application can perform fast and efficient Fourier transformation.
While not so modern-looking, the interface is fairly intuitive and provides you access to most of its functions. We recommend you also take a short look at the FFTExplorer's Help section that offers a number of step-by-step tutorials to better understand its functionalities.

Its ease of use recommends it as being a good educational tool

As far as customization options are concerned, FFTExplorer does not offer you much to hope for, as it only makes it possible for you to choose the values for the Sample Rate and FFT Array Size, and select their line colors.
All in all, considering its set of capabilities, its straightforward workflow and all the provided documentation, all these factors recommend FFTExplorer as being a comprehensive app. The application manages to strike a suitable balance between ease of use and efficiency.