In Episode 1 after we hear "THE MONSTER" Rose recognizes the sound she says:

Rose
That sound that it made, I keep thinking that there was something really familiar about it.
Redshirt #2
Really? Where are you from?
Rose
The Bronx.

http://www.losthatch.com/sounds/show_sounds/S1E01_Rose_Monster.mp3

THE MONSTERS SOUND

http://www.losthatch.com/soundtrack/s1/LOST%20-%20S1E01%20-%20Island%20Monster.mp3

This got me to thinking, what is unique about the Bronx.
The Bromx has a Elevated Railway. But obviously there is no elevated railway on
the island, and the trees were shaking alot, then i stated thinking about
subway systems.

Steam Powered Train Link (5 sounds)

http://www.joelstrainroom.com/pg_six_steamenginesnd.htm

Electrical Powered Train Link (1 zip file)

http://www.brdw.co.uk/sounds/mp3_d2062d3232-01.zip

Modern subways use a Rotary converter for power, heres a description

http://en.wikipedia.org/wiki/Rotary_converter

possible source of the magnitisim in the hatch.

some pics
http://www.nycsubway.org/tech/power/index.html

http://www.nycsubway.org/tech/power/rotary.html

comments plz

There's a thread about this on this board too. It was started sometime in the summer but no one has posted since.