Step 1: Stuff You Need
1. Computer (with Audacity and Visual Analyser)
5. Water bottle (and water)
Step 2: Range of Human Hearing
In Visual Analyser you simply click the "Wave" button above the scope window. Set the desired frequency, click apply, then click "ON". Notice the right and left channels are controlled independently unless you click the "Interlock" check box. You can also generate a sweep that will move through a whole range of frequencies. You can change the options for this in the "Sweep" tab.
Then go back to the main window, turn the scope on, and change the input in Visual Analyser from "Microphone" to your output (note, on my computer it is "Stereo Mix", but this depends on your computer). Then you can watch the Sweep in the FFT window, while listening.
The normal range of human hearing is 20 Hz to 20,000 Hz. Your sound card may not really be able to reach these limits however. As you vary the frequency you will find that the sounds in the middle seem louder. We tend to hear better in the middle of our range and not as well at the extremes. How high up can you hear? If you can't hear it (and it's still less than 20,00 Hz) ask a teenager before you blame your sound card.
When you get to the really high frequencies you'll find teenagers tend to wince while adults will hardly hear anything. Just crank the frequency up to around 17,000 or 18,000 Hz and you'll have the teen repeller. As we age our hearing deteriorates. We loose the extremes of our range first.