We had an office with a backdoor out into a tiny parking lot (~5-6 vehicles). There were guys with weed whackers. The sound kept going forever and ever and ever. Turned out that my coworker had subtly tuned the stereo (hooked up to a computer for streaming) to a YouTube video that was four hours of weed whacker noise. It took like 45m for someone to complain and he just started laughing uncontrollably and was found out. He’s a good friend and I’m still mad at him for that when I remember it. Ace job pranking us, though. The workers had been long gone.