If you live near downtown Seattle, you may have recently heard a long, low horn reverberating through the soupy nighttime air.
It happens every once in a while and has some Seattleites mystified. Where does the sound come from? It is a train? A boat? Last call at a Capitol Hill bar?
None of the above. It’s a foghorn.
“It is definitely loud,” said Captain George Capacci, deputy chief of operations and construction at Washington State Ferries. “I mean, I’ve stood many lookout watches, plugging my ears every two minutes.”
Capacci said the foghorn, also known as the signal horn, is used to warn other vessels to slow down and pay close attention when there is restricted visibility. Restricted visibility could be due to fog, intense rainstorms, snow and even sand storms. “Nighttime is not restricted visibility,” Capacci said. “It’s just darkness.”
He said vessels use lights at night to indicate their position and direction of movement on the water.
Most of the time, the foghorn sounds from the ship, not land. The captain presses the requisite foghorn button, which then emits a prolonged blast for four to six seconds. That blast is followed by another every two minutes until the ferry finishes the crossing.
Smaller boats sound one long blast followed by two short ones. Vessels that are anchored are supposed to ring a brass bell at intervals not less than a minute. To the trained maritime ear, it’s a system of boats and ships talking to each other across the water.
In an age of radar and high-end navigation systems, a foghorn might seem old fashioned. In fact, the big ships are in radio contact with each other and know where the other ships are. The foghorn is used to warn smaller vessels, such as fishing and pleasure boats that might not have sophisticated navigational equipment.
Because the sound wave from a foghorn travels over water, through still, moist air, it can be heard from several miles away. From that distance, the sound softens into a low mournful wail. Close up, however, the foghorn sounds more urgent, or like a saw plunging through a tree trunk.
Capacci said that in the days before radar and GPS, ships used foghorns to help them navigate.
“They used to use foghorns to measure distance with a stop watch,” he said. “They would sound the signal and then measure the time it took to hit land and bounce back. They would navigate with sound signals.”
Capacci, who has worked for ferry systems in Alaska, British Columbia and Washington, said the sound of a foghorn across the water has a certain romance to it.
“I think it harkens back to an early day, despite all our sophistication and electronic equipment,” he said. “You have all these horns sounding, that lets you know that there’s people on watch, keeping the water safe.”