In 1.2.5 My IC2 devices made noise by default (macerators running out of power drove me nuts). If I remember, at some point since then sounds were disabled by default until the bug could get fixed.
1.109 changelog says "fixed sounds"
DW20/MC packs both have had at least this version if my numbers aren't public school derived, but the sounds are disabled still. Was this a config default by FTB?