Step 1: Stuff You Need
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
Note, you want your hand above the microphone to get the most precise answer.
Step 3: Zoom In
Step 4: 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.