This thing is doing some fancy stuff, and it is free! A similar app, FFT, costs $25.
Spectral Eye analyzes incoming audio signals to extract the underlying frequencies. Most sounds are built up from a variety of sine waves; a simple whistle might be a single wave, while a guitar, piano, or the human voice have many waves added together.
By using a Fast Fourier Transform, sound can be decomposed into each frequency. Normally, this information is displayed on a chart, and there are number of excellent apps that do exactly this. Spectral Eye rearranges the FFT into a spiral, so that frequencies that are an octave apart are lined up as rays from the center of the display. The strength of each frequency is represented by the size of a red circle.
If you're interested in understanding the nature of sound, use Spectral Eye to get a better view. The app was created as a utility used in the development in other Secret Base Design apps; we're making it freely available, because we found it to be useful, and thought others might like it too.
The app will remain free, and will not have ads. If you find it useful, we would very much appreciate a review in the app store, and you can get in touch with us through our support site, our Facebook page, or Twitter.