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12th August at 11pm til midnight: the forecast was for a clear night, a good time to watch the Perseids shooting stars which come in August BUT it was very foggy instead and you may have heard the foghorns of 4 ships sounding with a mellifluous harmony in the night. My wife and I moved onto the balcony to appreciate the pleasure of hearing these sounds of our childhood when the lighthouses’ foghorns would lowly reverberate down the East Lothian coast (Bass Rock, St. Abbs, Isle of May for my wife) and the Ayrshire coast (Pladda & Ailsa Craig for me). There are no active foghorns remaining in the UK, however Sumburgh’s restored foghorn, last sounded in 1987, can be sounded on special occasions.

Photo 1: the ships offshore at the time they sounded their foghorns (credit https://marinetraffic.com).

Click <<READ MORE>> below to see photo 2: Ardnamurchan foghorn, credit https://uklighthousetour.com 

Now there may not be anything special about the Sumburgh Head Foghorn, but the people who restored it believe it to be the last working foghorn in Scotland. Sumburgh is in South Shetland. To sound the foghorn, the diesel engines are started  and air is compressed into large reservoir tanks at 25 PSI. Then a worker needs to go up a spiral stair case to the horn room and activate it from there. Every foghorn has it’s own unique sounding pattern, and it differs from other foghorn signals in the area, Sumburgh's horn blows for one 7-second blast every 90 seconds. This allowed ships’ captains in the area to know which horn is warning them. 

Listen and dream:  https://www.youtube.com/watch?v=WLlsRsUX78w

Question: Why are foghorns designed to emit their tones at such low frequencies?  Answer: Foghorns have very low pitches because sounds with low pitches have a long wavelength. This is important because a long wavelength means that the sound wave can easily pass around barriers, like rocks. This property of a wave is called diffraction. 

Question: What is the difference between frequency and pitch?  Answer: Frequency is the emission, pitch is your perception.

Question: How far away can you hear a foghorn?  Answer: about 20 miles


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