AudioXplorer is a powerful sound analyzer software designed specifically for MacOS X.
Real-time analysis: AudioXplorer provides real-time analysis window where user can visualize the amplitude and the FFT.
Static analysis: AudioXplorer provides static analysis window: user can record or generate any sound and performs operation on it (FFT and Sonogram).
Easy-to-use: AudioXplorer is very easy to use with it Aqua interface (several windows can be opened at a time, drag-and-drop support, view appearance can be customized)
AudioXplorer is discontinued and is now available for free.