As a surfer, let me volunteer that it's a bit like a highway onramp: you want to match speed exactly when the front arrives. Tiny adjustments in speed, pitch, yaw, roll, and center of gravity make the difference between making it, falling off the back, and getting eaten.
Mistiming your drop leads to bad outcomes that are directly proportional to the kinetic energy of the wave and are inversely proportional to the depth of the water. This is huge kinetic energy with a distance to the wall of, probably, microns. I want to see how this thing works, but oh, Nelly, what a wipe-out!
I'm somewhat new to surfing but am thinking this is slightly different than what you are imagining. I also know next to nothing about acoustics and wave forms.
Wouldn't the wave be the height of the tube, and the vehicle be near that same height? That way you can't "miss" the wave. Unlike surfing their is no room below the wave for the vehicle do dive and throw the surfer off, and unlike surfing , a soundwave (to my knowledge) doesn't break, so there is no tumble. If you enter at the point where you're off the back of the wave, you're positioned to be picked up by the next wave, which because your vehicle height is near equal to the height of the wave, your vehicle automatically gets pushed along.
That's how I'm visualizing it, but I could be wrong.
(experienced body boarder/body surfer, novice actual surfer ;-)
I think the point is that, regardless of which wave you decide to catch, whether it be the first or second one, at some point to need to sync-up. If you miss the first one, then you still have to speed up or you're going to miss the second one too.
There's definitely an optimal timing that takes the minimum amount of energy to accelerate and synchronize with the "sweet spot" of the wave; beginners need to paddle early and paddle hard, whereas an expert has a better feel for it and will exploit his or her experience with the timing to expend less effort catching a wave.
When you surf, paddling up to speed and the timing will make or break catching a particular wave - which is very important is the "good waves" are rarer. With an acoustic loop, it's may be more predictable, but you still probably want to get it right the first time, while you're still in the main accelerator section of the tube.
The difference between sound and water waves is that sound waves are longitudinal, ie the local displacement of the medium is parallel to the wave travel direction, while in water it is perpendicular. The wave thus does not really have a 'height', it would just fill the entire tube, and there wouldn't really be a way to miss it.
Mistiming your drop leads to bad outcomes that are directly proportional to the kinetic energy of the wave and are inversely proportional to the depth of the water. This is huge kinetic energy with a distance to the wall of, probably, microns. I want to see how this thing works, but oh, Nelly, what a wipe-out!