I know that there can be a lot of things that can factor in such as wind and terrain, but in general does anybody know how far a gobble can be heard from or is it even possible to determine this?

On a calm lake with a slight breeze coming from the bird to you I'm sure you could hear it from miles away. Last year I had a nice tom at 50yrds gobbling and I thought he was way off in the distance because of a strong wind at my back, I didn't know he was so close till I saw the fan cresting the ridge.
You said it yourself, the conditions control how loud they will be at distance.

like you said it all depends. later in the season when the vegitation is thick it gets tough. i'll hunt an hour and a half north where theres less/no growth and go home and think they are farther than they are...it can vary that much.

terrain, weather, cover etc etc all play into that. sometimes its 500yds..others its 200. all depends..

It really depends on three factors: barometric pressure/humidity (density of the air), elevation, and vegetation.

Hence, that's about 9 different scenarios, and hence 9 different answers

For extremes:

1) on a ridgetop, on a clear morning, before the woods green up---miles.

2) in a valley, slightly misting, late spring with thick vegetation---50 to 100 yards.

Of course, the other problem that is often encountered, is scenario (1) typically is the result of a high pressure system and the birds usually gobble their fool heads off, whereas in (2) the low pressure system really shuts down the birds, so there is also fewer gobbles to be heard. Wind can also be a factor, but usually only affects the ability to hear gobblers in extreme cases (30+ mph), which also has a huge impact on bird behavior anyway...

flat ground, calm conditions, turkey in tree, I say about 500 yds

well, gobbles can sound farther or closer depending on where you are. in the woods the will soundfarther away than they are cause the foliage and trees will muffle the sound. in an open field they can sound closer than they are. i watched 6 toms gobble at 400 yards away on a hay field and i could hear them fine. later that day i was int he woods and heard what i thought was a distant tom , then when i saw him 3 minutes later he was 45 yards away, then i shut him up and thats how i got my opening day bird this year.

I don't know how far away I can hear a bird gobble........but I do know that when one comes in behind me quiet in the wet grass or leaves, and decides to let one loose 10 yards behind me, you'll probably hear me swear in the next county from being startled out of my skin...

..don't ask how I learned this...[:@]