Headphones are worn over or in your ears to listen privately. A pair of headphones, noise-cancelling headphones, put your headphones on.
It is a plural-only noun, like trousers, so it is a pair of headphones. The noise-cancelling kind work by playing the opposite of the incoming sound wave, which works well on steady noise like an engine and poorly on speech.
1nounheadphonesA device worn over or in the ears for private listening.
“He put his headphones on so he could listen to music without disturbing anyone.”
headphones is a device.
Also accepted in games: earphones, earbuds, headset
From head + phones.
Etymology from Wiktionary, CC BY-SA