Always wondered how to judge the distance of a rifle shot in the woods. On average that is. I understand different calibers generate different sound levels, and that the wind can play tricks, and if there are mountain peaks between you and the shot . . . But if you are hunting flat, pine covered forest, how far can you hear a gun shot. You know the direction . . . now how far away was it?
1/2 mile? Mile? Any research done on this?

Humidity plays a factor into that. You can hear gunshots for a couple of miles if there isn't much ambient noise.

Well I'm at 9000+ feet in Wyoming and humidity is generally what other states get. Mostly dry here.

There's just too many variables to determine how far sound will travel and be audible to different observers (or rather, "hearers" in this case?). Sound gets dissipated very differently according to terrain, density altitude (temp, pressure, humidity), wind condition, terra surface, etc. Gunshots also have different combinations of frequency and intensity depending upon caliber, pressure, barrel length, etc. For example, it could be quite possible for a 45acp to have the same pitch/frequency as a 12ga shotgun, but the 12ga could be considerably higher intensity, aka louder so the pistol would sound identical to the shotgun if it were fired closer. A 30-06 at a mile away might sound similar to a 9mm at a quarter mile.

There's a lot of science you can tie to this to locate a sound based on echoes or transmission time between multiple spread points, and the relative volumes perceived at those locations, but by and large that's going to require intelligent software and a lot of intricate hardware. Not something you can do by ear.

Has there been research into this? Yes, and there are lots of technologies out there that have databases of different gunshot profiles, correlated against disturbance patterns for wind, terrain, and surface effect distortions, etc etc - in other words, it's a known art. Is it something you can do 'by ear'? Nope.

Thank you Professor.

I'll just keep on guessing then.

Nomercy448 hit the nail on the head.

I wonder if the animals know which direction the shot comes from, and if they react.

You asked the question, I gave the best answer I know to give. Physics is a passion of mine, absolutely fascinating, especially the physics of wave motion like sound transmission. My profession has had be cross paths with certain auditory instrumentation, and my personal life has seen many instances where I've been riding horseback or hunting out off of the grid and heard a gunshot, with many instances where I've grossly misjudged the distance due to estimating the wrong cartridge/firearm type - hence my interest in this topic in particular. I guess I don't see the sense in getting butthurt because someone gives an answer to a question you've asked.

The best I can do is tell what direction it comes from.

My observation is that the animals do not know where it comes from. I've seen animals, at a shot, stand and look different directions, mill about, run in one direction for a bit and the turn and run another, etc... As suggested above, with terrain, the sound is traveling all over the place. They seem to know the shot is not a good thing and I've noticed if the shot is not really close that they fairly ignore it, suggesting they may have an idea of the differences and value of danger or safety based on how loud the shot is.