# Under optimal conditions, how far could an emergency whistle be heard?

Whistles are often used for emergency signalling, it would be good to know how far that signal can travel and still be recognized.

There are plenty of factors that would affect the distance, so how far would it travel under optimal conditions and then one could figure that real world conditions would be less.

As starting point,

• I would refer to this answer from physics.stackexchange. physics.stackexchange.com/a/415426/9338
– user16724
Nov 9, 2018 at 19:12
• At first I thought your two facts contradicted each other, as it appears the sports referee whistling beat the world record, in which case the sport referee would be the record. But the first point probably implies "without a device to aid the whistler" - ie: which just the mouth as the whistle device. Nov 9, 2018 at 21:14
• I was going to provide an answer, however: I don't remember the formula for this, so I went to use an online calculator for it, and using the Storm Whistle (measured at 130 decibels, distance not provided in the source I read so I assumed 2 meters), the calculator I used provided an estimate of more than 2000 miles when I provided it the hearing threshold for the second point!!! Something is not right there (and it might be me), since I highly doubt it could be heard at more than 2000 miles. So no answer; but feel free to use this info in other answers. Nov 9, 2018 at 21:22
• Optimal conditions probably involve the right thermal layers resulting in a wave guide and could theoretically be 100s of miles. I think it makes more sense to look at typical comditions. Nov 12, 2018 at 1:28
• I used a whistle this summer and I can definitely say that the lower the pitch of the whistle, the better. We lost a hiker in a dense boreal forest bushwhack and started a search. The 'lost' hiker simply angled slightly to our left and was descending past a small ridge. When she arrived at the trailhead, we started trying to get the further guys back down. I could hear the furthest guy loudly calling with his deep voice. He and the guy below him never heard my Fox40 whistle even though I called for over 5 minutes. I ended up climbing and shouting at them. It was not even 500m away. Nov 14, 2018 at 15:15