speaker (audio), n.Trivia

All speakers can work as microphones and vice-versa; if you plug your headphones into a mic input, you can speak into them and use them as a microphone. The inverse is true as well.

New cars often play fake engine noise through their speakers for car enthusiasts since modern engines are so quiet.

Audiophiles were, when tested, unable to tell the difference between music transmitted over monster cables vs a coat hanger.