Pew science is trying. Measures sound data in milliseconds and uses said data to extrapolate relative back pressure.
Otherwise its the age old convention that to quiet a rifle you have to slow and hold the gas coming out the end of the barrel. Cans that do this the best are usually quietest BUT holding that gas in means it's holding inside the barrel and gas system as well. Which means you're gonna have more gas in your face. To alleviate, some manufacturers have turned to stepped apertures in their stacks and monocores. This allows gas to escape faster BUT thats gas that makes noise out the business end. Louder can with less back pressure.
The new hotness is DMLS (direct metal laser sintering) or in layman's terms, 3D printed. These designs aren't subject to a lathe or mill and those limitations. Huxwurx and CGS have been doing this the longest. A can like the Hyperion meters as well as the nomad L or magnus but has better flow characteristics. Still restrictive but better.
At the end of the day you get sound reduction or backpressure, no free lunch.
After you decide how much you hate yourself and your friends, pick a use case. A hunting can that suppresses 20 rds a year, you want weight savings. Go titanium.
Hard use that will eat mag after mag out of your 5 inch AR? Get a wonder metal. C300, inconel or stellite. Weight is gonna be whatever since you need the heavier material and it's properties.
Need a generalist that isn't gonna see super hard use? Find a can that leverages hybrid materials so you get some weight savings but won't lose your titanium stack if you get it a little toasty. These designs (sico chimera/omega) can do a lot but short barrels and Uber magnums are a no no.
All this to say, you won't stop at 1 can. Pick a use case and buy a silencer that best fills that case
