baudline

baudline is a realtime audio signal analysis tool which runs under the Linux operating system. Baudline has many useful features, such as tone, sweep, and noise generators, spectrum and waveform displays, equalization, frequency shifting, time scaling, and everything but the kitchen sink.

Some neat uses I've found for baudline:

• Using the spectrum analysis (with the FFT size set to 32768 points, on a fast computer) to calibrate the CTCSS tone generator on an old radio
• Checking the frequency response of mp3 and ogg encoders
• Generating pink noise to mask atmospheric sounds (setting AM modulation on the tone generator at about 0.3 hz makes it sound like crashing waves!)
• Making tele-evangelists sound like chipmunks (okay, the practical side of this exists only when viewed from a Discordian standpoint, I suppose...)

baudline is available free as a binary-only release for i386 systems at http://www.baudline.com

baudline's website and documentation do not capitalize its name, so I'm preserving that lack of capitalization here.