Wow! That's so stupid! Every thing: elevators, cars dashboards, computers, home appliances (conditioners, stoves, everything else), alarm clocks, electronic locks are using beep as a warning/attention signal. But really dangerous things got switched to a sound indistinguishable from harmless pneumatic system sound.,(reply>), @TalesOfWar 1. leaking air doesn't require attention. Any big pneumatic system is dumping air from time to time (because of compressor inertion). <br>2. As a professional sound designer I must point out, that city environments are essentially generating white noise and our brain is extremely good at white noise cancellation. Physically, white noise is difficult to mask by any frequency. But human brains historically are doing very well at cancelling it out, because white noise is generated by wind in trees, fast rivers, etc, it's an environment factor. On the other hand, human speech, animal sounds automatically triggers attention. You might sleep near roaring waterfall, but will wake up because of nearly indistinguishable human speech or predator howling. ,(reply>), +Nobody Quite I think this is mostly for construction sites. As someone else in this comment thread mentioned a lot of tools and equipment used on building sites use compressed air to operate, so hearing something that sounds like compressed air quickly escaping would alert workers as it could indicate that some piece of gear is malfunctioning and could cause harm. Also as said in the video, it's audible even in busy environments which construction sites most certainly are, not to mention many are in the middle of a crowded, loud city which makes matters worse. You think it's stupid, I'm sure the data proves otherwise.