Here's an interesting question that verges a bit into "psychoacoustics"... ie., not only what is acoustically heard, but what is musically intended.
Take a look at my screencap: It's a picture of a wave, of course, expanded a bit wide for better view. Specifically it's the sound of me cracking two wooden rulers together on their edges, for maximum sharpness. You're looking at one "hit" of the rulers. My living room is not acoustically treated, but nor is it especially reverberant.
QUESTION: Now, assuming I want to use this sample as an indication on my Timeline of where a specific beat in a 4/4 measure occurs.... Where, in this "clap" of sound would you consider my "psychoacoustic" beat to be? Where the first squiggle arises from the midline? The highest peak above the midline? Or the lowest extreme below the midline? (I've turned off the "Snap To" function of the Now-Time Indicator, so it can be positioned anywhere along the sample I'd like it).
Sure, I know I am splitting hairs here... but I'm just damned curious is all. Are there established proper names for these different moments in a sample, BTW?