When fog blankets Puget Sound, it sounds like a concert on and near the water. Sirens sing from piers, bells chime on rocking buoys and horns bellow from ships and bridges. The more traffic, the louder the band. And, like any concert, whether this sounds like beautiful music or just a bunch of noise depends on who’s listening.

Timothy Westcott of the U.S. Coast Guard describes the baritone blasts of a ship’s foghorn as “soothing and reassuring.”

“It’s a ship saying, ‘I’m here,’” Westcott said. “It’s important to the safety of mariners and the protection of life and property.”

Capt. Eric vonBrandenfels, president of Puget Sound Pilots, says foghorns, are a booming reminder that ships are vigilant about safety. He’s seen them save lives. VonBrandenfels once had to radio a personal watercraft that unknowingly had drifted into the shipping lanes near Port Angeles. It was the horn that alerted the small boat to maneuver away. VonBrandenfels said he could hear his own foghorn and a scream over the radio as he passed. “We use the foghorn regularly to alert boats that don’t see us,” he said.

Lou Paulsen, the Port of Tacoma’s director of strategic operations projects and risk management, hears a universal language. “It doesn’t matter what language a mariner speaks; they understand these sounds.”

Phil Morrell, vice president of marine operations for TOTE Services, also hears safety and a healthy heartbeat of industry. TOTE Maritime Alaska has operated in the Pacific Northwest for 45 years and is no stranger to extreme weather. “Foghorns are an indication that our state’s domestic maritime industry is functioning safely to reliably deliver cargo to help sustain our state’s consumers, businesses and economy,” Morrell said.

FileContainer ship fog horn

Do we really need foghorns if ships have radar?

For some, the foghorn is nothing more than noise. Just ask the Port of Tacoma’s Public Relations Manager Leslie Barstow. On mornings after foggy nights, she expects to have a few messages from people annoyed by the sounds. One morning in 2016, she received 32 messages. One of the most frequent questions: Do we really need foghorns if all the ships have radar?

The short answer: Yes. Not only are sound signals such as foghorns required by federal and international laws, but they are an important navigational and safety tool. Horns can warn boats away from ships, structures and areas where they might run aground. And mariners can use the sounds along with their charts to navigate when their view is impaired by fog, smoke and heavy rain.

Westcott isn’t surprised that people are sometimes bothered by the noises. Foghorns are intentionally loud. Foghorns on a 200-meter-long (nearly 656 feet) ship must be loud enough to be heard two nautical miles away. Fog can reduce the range of the horns, he said. But he says the annoyance usually fades once people learn the importance of the sound signals.

“It’s like when a train blows its horn when it goes through a busy town,” Westcott said. “We understand this is to keep people safe. That’s what ships are doing.”

Source: U.S. Coast Guard

Sound Signal Intensity

Vessel length in meters Audibility range in nautical miles
200 or more 2
75-200 1.5
20-75 1
Less than 70 0.5

What else are those horns saying?

There is a lot of information packaged into the blast of a foghorn, which blows every two minutes when vision is impaired by fog, smoke or heavy rain. Even to the untrained ear, the message is clear: “Get out of the way.” But a mariner hears more.

The type of sound signal can indicate if a ship is underway, stopped, has restricted maneuverability, is being towed or is aground or at anchor. And the unique blasts of horns and sirens on fixed points can help mariners navigate.

For example, a boat approaching the Tacoma Narrows Bridge in the fog might not see the massive spans, but it will hear the horns. Both bridges have foghorns at each end and all four emit a unique blast sequence. Mariners can determine their location in relation to the bridges by using their charts and a Coast Guard-published reference manual called the Light List, which includes the blast sequence of every fixed-location foghorn.

Source: U.S. Coast Guard

What do the Sound Signals Mean?

Sound signal The vessel is…
1 prolonged blast at intervals of no more than 2 minutes A power-driven vessel making its way through the water.
2 prolonged blasts (2 seconds in between) at intervals of no more than 2 minutes A power-driven vessel underway but stopped.
1 prolonged blast followed by two short blasts at intervals of no more than 2 minutes

Not under command, is restricted in her ability to maneuver, constrained by her draft, sailing, engaged in fishing or towing or pushing another vessel.

At anchor and either engaged in fishing or restricted in her ability to maneuver.

1 prolonged blast followed by three short blasts at intervals of no more than 2 minutes Manned but being towed.
Bell ringing for 5 seconds in intervals of no more than 1 minute (Sometimes followed by a 5 second gong) At anchor. If the vessel is 100 meters or longer, the bell will ring at the forward end of the ship and it will be followed by a gong sounding for five seconds in the aft.
3 separate bell strokes, 5 seconds of bell ringing, 3 separate bells strokes in intervals of no more than 1 minute (Sometimes followed by a 5-second gong and a whistle) Aground. If the vessel is 100 meters or longer, the bell will ring at forward end and it will be followed by a gong sounding for five seconds in the aft of the ship. The vessel may also sound a whistle.
4 short blasts following one of the previous sound signals A pilot vessel engaged in pilotage duty.

Could Tacoma Narrows foghorns turn down the volume?

The foghorns on the Tacoma Narrows Bridge are required to cast sound that can be heard for 0.5 mile, but the sound can echo off the steep shoreline slopes. The Washington State Department of Transportation (WSDOT) has heard complaints from the community and is working with the Coast Guard to reduce the sound.

“It’s a balance between getting them so they are not so annoying, but still audible enough because they are an important safety measure,” said WSDOT spokesperson Cara Mitchell.

That, essentially, is the other unwritten message carried across the water by those deep foghorn tones. Not only do these sound signals keep people safe, but they are helping avoid the environmental devastation of a shipwreck.

“We recognize there is an inconvenience of noise, but it is an important layer of protection,” Paulsen said. “It is prudent to have redundancy.”