SD's 1/2" Valve Flow Control (Dump) ???

Running those filters, not sure what but they are like porcelin or something. They work really well too. They dont get very clogged and they protect your valves from getting dirty.

you should try some adjustable silencers used on phnumatic cilinders like smc or norgen . they use them all the time on industrial machinery . dont no where you would get them from coz i live in the united kingdom but its worth checking it out