The chirp you just played varies in amplitude over time. We started off looking at very simple waveforms that didn't vary in time. But sounds come in all different shapes and sizes and can change over time in some very interesting ways. Now let's look at some familiar waveforms and one new one using our trusty oscilloscope.

We have already seen the triangle wave that ramps linearly from the minimum value to the maximum and back again. Also familiar is our square wave, which jumps instantly from the maximum to the minimum. Here we also include a sample of white noise. White noise varies randomly throughout the interval from maximum to minimum. You should be able to hear a "pitch" from the triangle and square waves: as you increase the frequency, either sound will seem "higher," and the pitch should be about the same for both waveforms. But white noise has no pitch because it contains equal amounts of all frequencies.