In the very extensive sound setting, there is no way to turn down the noise from certain Redstone machines like Droppers or Pistons without just turning all sound to its lowest setting. I wouldn't call this a bug but it very clearly is an oversight, maybe just add one more slider bar for "Redstone Machichinery" or attach it to the same slider bar as Jukebox/NoteBlocks. I was kind of confused that no slider would change that volume at all unless I just simply didn't want to hear anything.