Raven

Raven is a software application for the acquisition, visualization, measurement, and analysis of acoustic signals.

Raven has been developed by the Cornell Bioacoustics Research Program, with the support of the National Science Foundation, to provide a powerful, user-friendly research and teaching tool tailored to the needs of biologists working with acoustic signals.
The Raven download is a demo version (it lacks the ability to save files, and runs for only ten minutes at a time) of the full Raven product. To enable all features of Raven, you must purchase a license. However, this is a free Requirements
PPC, Mac OS X 10.2.3 or later, Apple Java 1.4.1 or later Recommended: 400 MHz G4 processor or faster
Related Links
Also available, Raven Lite, for hobbyists. $45 (USD)