Earphones

Earphones, also known as earbuds, (COMIC: Fear Buds) were a portable form of headphones fitted to the outer ear. Like headphones, earphones were primarily used for listening to audio privately.

History
While working for Harold Saxon, Miss Dexter used earphones to listen in on phone calls between Martha Jones and her mother Francine Jones. (TV: 42, The Sound of Drums)

Lucy Skinner listened to indie music with her earphones. She downloaded music from the bands Women of War, Rain Green, Giddy Nuisance and The Motorboats onto the computer at the Tycho Project. Her father told her off, and Lucy promptly took out her earphones and apologised. (TV: The Last Sontaran)

In 2007, C'rizz once attacked bystanders in King's Cross station. Luke Tillyard, discovering that Charley Pollard was running from C'rizz, used the earphones from his MP3 player on C'rizz which rendered him unconscious. (PROSE: Salva Mea)

After Prisoner Zero escaped from an Atraxi extra-dimensional prison, the Atraxi hijacked the electronics of Earth to broadcast a warning ordering Prisoner Zero to vacate or "the human residence will be incinerated". A Leadworth woman was confused when she heard the Atraxi warning through her music player's earphones. (TV: The Eleventh Hour)

When a plate-sized Virtual ship crashed in London in 2011, the Virtuals escaped by uploading themselves onto the internet via a music track called "Alien Infiltration". This caused several people who listened to it through earphones to enter into a trance and walk out into the streets until the Eleventh Doctor deleted the Virtuals from the internet server and sent them back to their own dimension. (COMIC: Sound Bytes)

After being caught listening to music on earbuds at school, Ralph used Mkali technology to send out a jamming signal to all other earbud devices. This interfered with the brain waves of his classmates, allowing Ralph to control them through their earbuds until the Twelfth Doctor intervened. (COMIC: Fear Buds)

The C-Fish was a portable music player developed in the 2020s which had tiny earphones. Jack Harkness stored a C-Fish X20 in a locker at King's Cross as a Time Agent. He retrieved it in 1967 when he was working for Torchwood Three, just because he wanted to listen to some music. (PROSE: Trace Memory)

Other realities
On Pete's World, the EarPods produced by Cybus Industries served as that universe's equivalent of the earphones of the Doctor's universe, with similar functions such as allowing their wearer to listen to audio and communicate. Like earphones, the EarPods were also fitted to the wearer's ears. However, the EarPods were much more technologically advanced, also allowing their wearers to download information into their brains as well as serving as covert mind control devices. (TV: Rise of the Cybermen, The Age of Steel, PROSE: EarPod)

In the Shadow World, the Twelfth Doctor used earphones to listen to an audio transcription of the Veritas text via a laptop, which he could not read due to his blindness sustained at Chasm Forge. (TV: Extremis)