Another great comment! I think all of my .22 ammo, is the Thunderbolt by Remington, so knowing supersonic ammo is still so quiet is awesomeI have no opinion on the Obsidian 9, but I do have thoughts on the Sparrow.
The Sparrow is a good can that is really good for the size. Out of my RPR with subs, all you hear is "click..........thwack" when shooting it. With supers out of a Mk IV 22/45 Lite it is about as loud as a CO2 paintball marker, gassed to 300 fps. With supers out of a bolt gun, you hear the supersonic crack more than anything.
Cleaning the Sparrow is easy due to the monocore design. It also breaks down really easily when fouled.