Those living near to the port and perhaps on other parts of the island recognize the blasts of the Mirtidiotissa ship whistles. At 102 meters Mirtidiotissa is a “Class II” vessel according to regulations set by “ColRegs” – International Regulations for Preventing Collisions at Sea. “Class II” vessels are required to have a whistle (horn) whose fundamental frequency (pitch in music) is between 130 to 300 Hz. Larger ships have lower frequency requirements and smaller ships have horns pitched higher.
As the captain of the Mirtidiotissa seems to really like his whistle, we hear it a lot on summer afternoons in Skopelos. He is especially heavy handed when there are smaller vessels (the obstructive rental sailboat fleets) in potential danger from the arrival of the ferry into the port.
These particular horns are manufactured by Kokum Sonics in Sweden and are part of their “Tyfon” line of different pitched analogue whistles. Mirtidiotissa carries two SuperTyfons (link) which are pitched at 165 hz (a low “E” in music). Capable of 148 decibels (dB), the two horns seem seem to be pitched at slightly different frequencies (Hz) which, (I theorize) because of their dissonance, help to project the sounds further. My theory is of course open to debate.
To me the “received frequency” of the horns is a sound in between “E” and “F” on the musical scale. Pitch is affected by the position of the horns in relation to the listener as in the “Dopler Effect” where the steady frequency (pitch) of an emitted sound of police car seems to change as it passes the listener. There are also environmental and geographical factors affecting “received frequencies”.
The analogue horns, in which a physical “thing” vibrates to cause the sound, are for more satisfying than the “Doop” made by the electronic horns of the Flying Cats and Dolphins. Personal opinion.