One rumor that persisted throughout the 2016 presidential election was that Democratic presidential nominee Hillary Clinton was being fed lines via a secret earpiece worn during one or more of the presidential debates. While there are many variations of this claim, none of them has proved true.
A new wrinkle appeared on 19 October 2016, when a video was circulated online that purported to capture the sound of an anonymous person whispering the word "dozens" through Clinton's earpiece during the third presidential debate:
The audio featured here is real, and can be heard at the 1:52:55 mark in the video embedded below:
The claim that the audio came from Clinton's earpiece (much less that it definitively features a mysterious person saying the word "dozens") is problematic. The noise is indecipherable, even when the video is slowed down, and if Clinton were being helped via a third party, that point in the debate would be an inopportune time to risk detection; — Clinton was not stumbling on a major talking point at the time, nor did she appear to be searching her memory for a key piece of information.
Determining the source of this noise may be as simple as watching the video. Clinton's mouth moves at the same time the indecipherable noise can be heard, so it's much more plausible that the microphone picked up a sound Clinton made with her lips.
At any rate, the entire theory rests on the notion that Clinton wears a secret earpiece during the debates, a rumor that we have repeatedly debunked.