Au'Ra: Earrings?

[x754]

Anything that actually touches an Au'ra's horn is probably selectively silenced. You can imagine all the sound generated by long hair or hoods as they rub against the horns, or sounds generated by touching other objects with the horns. Most sufficiently evolved animals have selective hearing systems in the brain, which process sound volume according to context. (This is how animals are able to deal with loud noise during the day, but use significantly improved hearing to avoid quiet predators during the night. This is also the reason why people can sometimes have difficulty falling asleep because they think there are loud noise: the brain is improperly changing the volume control before they fall asleep all the way.)

[Megad00mer]

Same way our weapons magically adhere to our backs/thighs with no visible straps or sheaths.

[Kaiser-Ace]

Same way our weapons magically adhere to our backs/thighs with no visible straps or sheaths.

Telekinesis?

[CGMidlander]

If I remember correctly, Auri horns are connected directly to the brain and are how Auri hear. The horns, which are not the solid bone that most people think (they are actually hard flesh), pick up vibrations and transfer them to the eardrums directly.

Sounds like a pain to sleep with (no pun intended)