The point where the volume from any given audible source (i.e. music, movie, television show, etc.) reaches and/or exceeds an acceptable level for enjoyment and is indeed no longer enjoyable by anyone.
Yeah, it was real relaxed upstairs at 20th last night until the movie reached Garrison Level.

Dude, turn that music down, we're approaching Garrison Level here, I like having eardrums.
by slickwillypie May 5, 2010
Get the Garrison Level mug.