High-pitched frequencies, rhythmic thumping, or distorted mechanical sounds intended to cause discomfort or "brain fog" in the viewer.
While there is no single "official" version of the video—as it is largely a digital myth—the descriptions usually follow these tropes: LULU-181.mp4
Many versions of the video circulating today are actually edits of older avant-garde films, 1980s Japanese TV commercials, or "found footage" horror projects. 1980s Japanese TV commercials
A sound file said to cause psychological distress. LULU-181.mp4