NounNah, I'm with Rusty on this one. If it get's heard, it's a sound, otherwise it's just a vibration.
1. Vibrations that travel through the air or another medium and can be heard when they reach a person's or animal's ear.
Also +1 on the shoelace site! I think you (or someone else) posted about it a couple of weeks ago. My mind was blown then, too. Can't believe I'd been doing it wrong all those years. The whole website is great too. Reminds me of the early days of the web when all sites were like that - a little odd, about random things, where the author is clearly very passionate!