How far away can you hear a helicopter?

[Mahatatain]

Thanks for all the replies people - very interesting and useful information/experiences.

Mahatatain.

[ArmySGT.]

A Huey doesn't fly, so much as it beats the air into submission.

[WallShadow]

Not sure how far, but Radar O'Reilly always had about a 30 second lead on the normal human ear when it came to the incoming wounded.

[bobcat]

drunk and dead tired on the sunday night of a four day weekend in korea i could still ID blackhawks, huey's, and shithooks 5 miles out so it would take an awareness fumble for anything in a helo to be sneaky.

[Graebarde]

A Huey doesn't fly, so much as it beats the air into submission.

I definately like that.. lol

[Adm.Lee]

Altitude may have something to do with volume, the lower to the ground, the louder it gets.

The house I grew up in was under the small-plane landing pattern for the city airport, and an Army Reserve Huey company was based there. If they were climbing away from a take-off, it was a sedate bup-bup-bup-bup. If they were descending for a landing, it boomed a lot louder, echoing off the houses. If they were really low (I can remember on at least one clear day in my side yard, being able to see the pilot's feet on the control bar through the nose glass), the windows rattled, the house shook, and the freestanding bookcases in the living room would rock back and forth. BAMABAMABAMABAMABAMABAM! It could drown out the lawnmower I was pushing.

We felt a small earthquake once and I saw the same bookcases rocking, but couldn't hear the chopper.

Strangely, I can remember once they landed one of the choppers at my elementary school for a special Bicentennial event (remember 1976), and I don't remember the bird landing in the same schoolyard being as loud as a few of the times they came over my house.

[ArmySGT.]

air temperature affects too

Cold dense air carries sound better.

[Sanjuro]

I get a lot of helo traffic over my house; mostly civilian, a good number of Chinooks passing to the North, plus police, HEMS, etc: the surprisingly quiet visitor turned out to be an AH64D! I guess a lot of work has gone into that rotor to keep the noise down...