You could have downloaded 1D Fast Fourier Transform 6.0 from our software library for free. The most popular version among the software users is 6.0. The software lies within System Utilities, more precisely Fonts. This free software was originally produced by Brown University.
From the developer:
The Fourier Transform is a powerful tool allowing us to move back and forth between the spatial and frequency domains. This applet helps students feel comfortable, helping to build a strong intuitive grasp of how signals in one domain correspond to signals in the other.
Students can load scanlines from common image patterns and see that scanline's Fourier Transform in real-time.
You may want to check out more software, such as Fast Sound Recorder, Fast Rabbit Typing or Fast Email Sender, which might be related to 1D Fast Fourier Transform.