One neat idea from Neal Stephenson's Anathem (with likely analogues elsewhere) is essentially a chatterbox that records people speaking in a conversation, chops

One neat idea from Neal Stephenson's Anathem (with likely analogues elsewhere) is essentially a chatterbox that records people speaking in a conversation, chops up the audio into syllables, and plays those back at random to foil eavesdroppers. This might work better than white noise, assuming you trust the computer that's doing the scrambling!