You're not the only one Ron, I do exactly the same too.In lieu of an official clapper, I usually clap my hands together 3 times to get a good visual cue and spike. Why 3 times, I haven't a clue.
As to why three times, I think its a visual thing. Its easier to sync 3 audio spikes together than one, if you make an error with one, it will show on the other two.
...and now back to the Monty Python sketch..
this topic kicks...ass
Joe