Thats an interesting thing to bring up and I guess my follow up to that would be how do you know you have the "right" brace height? I read somewhere that you keep tuning until your bow is as quiet as possible but that's difficult to judge quantitatively without an instrument.
Also, does changing the brace height by say a quarter of an inch really affect how your bow shoots? I mean it only really affects your idle weight and maybe your draw weight by a teeeeny amount. At what level archer and distance would you be able to really tell that your brace height is "off"?
Google brace height tuning, or search in AT.
But essentially sound, vibration, and if you are consistent height of impact. Your bow will likely be most efficient at the right brace height so the most energy will be transferred into launching the arrow. Thus the first two will be minimized, and the last should be optimized. Shoot a bunch of groups at say 30 or 50m. Chart the center of each group. Adjust brace height, keep going. You will likely find, if you start out low, your group centers should slowly move up, and at some point they will peak. That should be your optimum. That takes a lot longer than going by sound, and is likely to only be marginally more accurate.
Cheers
