"<a href=""https://www.youtube.com/watch?v=fa28lIGuxq8&amp;t=1m14s"">1:14</a> exactly. It's distinct and reserved for reversing heavy equipment. Meanwhile the "white noise" stuff could be mistaken for air release from a compressor", radio static (engineers use sim card walkie talkies, those make weird noises sometimes) etc.,(reply>), Have you heard the sound IRL? It's very loud and distinctive.