I will go through a process that will allow you to determine the speed sound travels. This is a classic physics lab that in the past would have required lots of expensive equipment. The only expensive equipment involved here is a computer with a microphone input. Which by itself can be expensive, but most classrooms these days have at least one in the room.
Step 1: Stuff You Need
1. Computer with microphone input
2. Microphone you can plug into the computer
3. Long tube. I typically use discarded carpet tube (which is free), but you can use PVC pipe. 1.5 m to 2 m in length is best.
4. An audio recording program. I recommend Audacity. [http://audacity.sourceforge.net/]
Step 2: Record Your Sound
Stand the tube up on a hard surface or place against a wall. Hold the microphone right at the opening of the tube. Start recording in Audacity. Snap your fingers near the microphone. A weak, pathetic snap tends to work better than a strong one. Snap a few more times so that your odds of having a good one will increase.
Note, you want your hand above the microphone to get the most precise answer.
Step 3: Zoom In
Click and drag over one of the peaks and zoom in. The easiest way is to click the "Zoom to Fit" button.
Step 4: Zoom In Again
Now you should see two sets of peaks. If you still only see one, highlight a smaller area and zoom in again.
The first set of peaks is your snap. The second is the echo of your snap.
Highlight just the two sets of peaks and zoom again.