Spectrograms can be useful to visualize the frequency content of sounds, and to give a rough-and-ready approximation of the activation pattern a sound is likely to generate across the auditory nerve array. For classroom demonstrations, or just to explore sounds, it's nice to have a piece of software which will record sounds from the microphone of your computer and will display the spectrogram online on the computer screen. One nice freeware program for that purpose was created by a company called Visualization Software, but their website seems to have gone off air (perhaps the company ceased to exist). This screenshot shows the program in action, visualizing the spectrogram of me pronouncing the vowels /a/-/e/-/a/-/e/-/a/ . The change in formants as well as the harmonic of the vowels are showing up clearly.
As it is a very nice and useful little freeware program I am making the installation file available here. It's a Window's program. It comes with absolutely no warranties! My virus checker thinks it's kosher, and when I've used it for lectures and classroom use it has always performed beautifully (kudos to the folks from Visualization Software!), but use it at your own risk (and since I am not the author, please don't send me any bug reports - I would not know what to do with them).