From out of the black hole

It's very dependent upon terrain. Soft dirt and woods while the tree frogs are awake may make it difficult if the person even comes within 20 feet of the hole. Also it makes a difference if the rescuer is searching/ listening when the victim is yelling.

I'm guessing you'd have to have a very good set of lungs, and the rescuers would have to be very close (within a few feet) to the hole. 40 feet is a long way down. The dirt sides would absorb a lot of the sound rather than channel it.
If the well had steel sides, the walls would channel the sound and amplify it. It may help the situation, butthe rescuers would still have to be close.

Define "A few feet from the hole" - three feet? Yeah, no problem. I mean, you're standing three feet from a hole that someone fell down into, and you can obviously SEE the hole - so yeah, you could probably hear them.

Ten feet? Maybe not. Much will depend on the size, shape, texture and composition of the walls of the hole. The hole is essentially a 'megaphone' focussing the sound STRAIGHT UP out of the hole. Depending on the diameter of the hole, and what the walls are made of, you might get a 'cardioid' shaped sound pattern just out of the entrance, or you might not.

Hard, stone like walls would tend to create an echo, possibly even reinforcing it - soft, turf like walls would absorb the sound - muffling it.

WriteKnight said:

Define "A few feet from the hole" - three feet? Yeah, no problem. I mean, you're standing three feet from a hole that someone fell down into, and you can obviously SEE the hole - so yeah, you could probably hear them.
.

Click to expand...

Not really...Of course it depends upon terrain, in Kentucky the ferns in the spring and the poison ivy in the summer an fall would hide the opening unless you are right on top of it.

Okay, funnel shaped megaphone with stone walls... and what sort of top? I mean, is there a rim around the well... maybe four feet high - like a storybook picture of a well?

Basically, the stone walls and shape will act as a reinforcement - just like a megaphone does. But sound won't trave OUTWARD untill it passes the 'lip' of the well. And then, it might be cardioid (heart shapped) or more omni-directional (round shaped) in its pattern, depnding on EXACTLY the length of the well, and the diameter.

If the lip of the well is higher off the ground, then the patter of sound might not emerge untill higher in the air above it, and the farther away, the less likely a listener will be in the pattern.

If it were my scenario - based on what you've described - I'd say the person tweny feet away could 'hear' the echo, but not understand it - the person shouting down the well would hear it clearly. Make sense?