My first instinct would have been something like that, but on second thought, I'd start with a example of a boat moving in water and the waves it makes, maybe drawing a picture and ask them to visualize it. This is admittedly very crude and inaccurate, but gives a good overview of the phenomenon. After that I'd elaborate on the differences of surface waves vs. pressure waves, wavelength & frequency and anatomy of hearing etc.
Generally speaking (and not directed against anything anyone has said): give the explainee an intuitive framework to hang details...
Heikki, 30, Finnish student of computer engineering. Found Less Wrong by via the IRC-channel of the Finnish Transhumanist Association, which was found by random surfing ("Oh, there's a name for what I am?")
As for becoming a rationalist, I'd say the recipe was no friends and a good encyclopedia... Interest in ideas, unhindered by the baggage of standard social activities. One of the most influential single things was probably finding evolution quite early on. I remember (might be a false memory) having thought it would sure make sense if a horse'... (read more)