Board Thread:Bug Reports/@comment-35166534-20180331210029/@comment-35699267-20180527002257

I think it's because Mojang removed the old sound files, as the older versions of the game are unsupported nowadays. When your Technic Launcher tries to get them for you they're just not there. This thread has a download link. Just drop them into your resource pack folder. Instructions are here: http://forums.technicpack.net/topic/321068-no-sounds-fix/