Great idea! I had thought about molds as potential earplugs but know that most of them are vented to some extent and didn’t know how that would work out. So plugging them is a great idea.
As I previously mentioned, though, for all the expense and technology, HA OEM’s, etc., could just as well rate the noise-attenuating potential of a dome or a mold if properly fitted and used. Just like a foam ear plug, it might not work as well as advertised and live up to its potential but at least if you knew the maximum potential, you know that you’re not going to get any better than that. Say at a Kiss concert then, you pull out your phone and it has a reliable sound meter app on it. The concert is 130 dBA average. Your molds or domes (even when plugged) are only officially rated by your HA OEM for 20 dBA avg reduction. So you know at best you’re still going to be getting 110 dBA exposure for x hours - and maybe if you use the NIOSH REL standard, you know you’re going to be suffering some hearing loss anyway. (Hearing loss is slowly cumulative and not reversible, as we all know, when you supposedly exceed the recommended limits and probably still happens to a lesser extent when you’re below the exposure limits, anyway. It just a matter of how your “bank” balance is going to grow over your lifetime. Higher exposure, you earn a higher “interest” rate and you get a bigger “payoff” in the end).
So I’d rather go with ear protection that’s officially rated and I’d be happy to rely in part on my HA equipment, the more so if it could be officially rated but perhaps HA OEM’s and providers don’t want to go there for liability issues, etc.
P.S. I would say the advantage of my noise-canceling over-the-ear MS Surface headphones versus plugging mold vents is that I can with two independent earcup dials dial up the exact amount of noise cancellation that I want and independently dial up the streaming volume - one is not coupled to the other. I can also switch to amplified environmental listening at the extreme noise cancelling limit - that’s not terribly good - Microsoft should improve the environmental listening. But it’s a lot of control along with very good CERTIFIED hearing protection. There is the bulkiness factor but then 1/2 the folks at Gold’s Gym seem to be wearing Apple AirPods (or whatever they’re called) or Beats Headphones. So if one could capture the Apple coolness factor in the right device, maybe everyone at a rock concert wouldn’t mind being seen wearing a device that certifies that they have Apple-like coolness but also certified hearing protection tuned to the level of the concert that they want to enjoy - and no ear pain, ringing, down payment on a hearing loss the next day.
Edit_Update: Discovered, though, that headphones are TERRIBLE to wear while running. Haven’t run in a long time due to a series of minor operations (cataract, gum graft surgery, etc) and took to stair-climbing and walking on treadmill on 7% incline @ 3.5 mph since then. Today went back to running and HA’s alone would definitely be better for that - headphones vibrate terribly and possibly add bad noise levels even when trying to run as smoothly and quietly as possible. Perhaps lighter weight gun muffs would be a suitable substitute just for blocking noise with streaming direct to HA’s or I’ll go with gr8dane604’s suggestion of getting molds & blocking vents.