That's why you can hear the ship's whistle in the fog

That's why you can hear the ship's whistle in the fog

Several residents contacted the Port of Kristiansand last night after hearing loud signals from ships at sea. The sounds come from ships' signal horns – often called ship's hooters or "tyfoons" – and are used to ensure safety when visibility is poor.

The area has been experiencing advection fog for the past few days. This occurs when warm air moves over a colder surface, causing fog to form. Combined with low winds, this can cause very poor visibility at sea. In some places last night, visibility was down to around 25 meters.

When visibility is this poor, ships are required to use sound signals to alert other vessels in the area.

Mandated by the Maritime Regulations

At sea, a separate set of traffic rules applies, called the Maritime Rules. These regulate, among other things, how ships should navigate in difficult conditions.

Rule 35 of the Norwegian Sea Rules of the Seas stipulates which sound signals ships must use when visibility is reduced, for example in fog. The rules state, among other things, that:

"A power-driven vessel moving through the water shall give a long thrust at least every two minutes."

This means that ships moving in fog must sound their horn regularly to warn other vessels.

Important for safe navigation

Large ships use a powerful signal horn – a so-called typhoon – that can be heard several nautical miles away. The signal is an important part of safe navigation and allows other vessels to detect the ship even when visibility is very limited.

Last night, Color Line used a sound signal upon arrival from Hirtshals around midnight, and in the morning hours, the cruise ship AIDAnova did the same while sailing into Kristiansand.

– When the fog lies thick over the fjord, such signals are absolutely necessary to ensure the safety of both the ships and others traveling at sea, says Isabelle-Louise Aabel, communications manager at the Port of Kristiansand.

Although the sound can be perceived as loud on land, this is a legally required safety measure when visibility is poor.