x1 is a headphone/earphone/earbud/hearing aid/hearing device for hearing x2 against background noise x3, the device being of form x4.
Refers to a device or portion of a device which covers/interacts with a single ear; for a headset (set of two such device possibly plus connective parts), use "tinytcici'e". Includes earhorns and other classical/passive devices; may also include ear-mufflers which diminish noise from entering that ear (such as, but not necessarily, for the sake of hearing something specific out of the other ear despite ambient background noise) - many modern earbuds serve this function to some extent anyway. Listening devices may be different from this (they listen and record/transmit sound elsewhere).