mavracer is correct, the port noise on an AR that's actually cycling is going to be at least mid-130s dBs, higher as the gas system gets shorter.
As such, for AR hosts, we generally recommend our 6.2-7" Valkyrie 36 or Aquilae 375. Bolt guns, on the other hand, there is a real benefit to running the 8-9" versions. Subsonic out of manual actions suppresses very well, supersonic loads do have a decent crack to them, more than high velocity rounds like .308 due to the wider & more blunt projectile at lower velocity.
We sold the last Valkyrie 36 we had on hand last week, but I do have stainless .375 cal Aquilae in 6.5" and 7", and 8 & 9" Accipiter 375 on hand. I am out of all titanium .375 cal models at the moment.
These are rated up to and including the .375 RUM & .378 Weatherby mag, can handle full power .350 Legend at any barrel length.
Black Friday sale starts tomorrow & runs though noon on Tues, 11/28. Friday will be the biggest discounts.