This headcanon was actually requested by my good friend, MasterClass60. She's proposed to me the notion that Techno Trolls purr when they're feeling extra-relaxed. This purring can become louder if the Techno Troll in question is in tune with their heart.

  Me? I think this headcanon is really cute, and I personally think that Techno Trolls could also express excitement by squeak-chirping like a dolphin.