SAN FRANCISCO (KCBS) - After 75 years, it's easy to take for granted the foghorns booming from the Golden Gate Bridge as the legendary fog rolls in. Some in San Francisco's Marina District even consider them a nuisance.
The man behind the signature moans that steer ships to safety and that's come to define the Bay Area is Jim McKnight, chief electrician at the Golden Gate Bridge.
McKnight has been blasting the 104 decibel horns - about the same loudness of a mower or power saw - for the last 15 years.
"If you can't see the bridge down below, then we need to have them on to let them know where the bridge is," said McKnight.
KCBS' Doug Sovern Reports:
Two lower pitched foghorns at the South Tower and 4 higher-pitched ones halfway across the span advise cruise ships and cargo vessels where to set course. Ships are told to steer between the 2 different tones to avoid hitting the bridge.
Nothing says San Francisco like the clang of the cable cars or the cracking of the crab at Fisherman's Wharf. But just having the fog sweep through does not guarantee McKnight will activate the bridge's mournful wail.
It all comes down to how low the marine layer is as it enters the Bay.
"A lot of time, you can't see the bridge, and we don't have the fog horns on because," McKnight said, "the channel is clear below."
Once upon a time, the foghorns were switched on manually. Now they are triggered electronically from a computer in the control room.
April may be the cruelest month, unless you find the foghorn cloying. Last August was one of the foggiest ever. For 28 days, gray poured in from the sea.
"We had periods of time where they were on 3 days straight," McKnight said. "It just didn't clear."
And unless it's necessary, they do turn them off at night. Otherwise, "we get complaints from the Marina," McKnight said.
March has the least fog. When ship captains can see clear across the channel, McKnight said he gets wistful for that lonesome moan.
"Oh, I love that sound."
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