A whistle shall be placed as high as practicable on a vessel in order to reduce interception of the emitted sound by obstructions and also to minimize hearing damage risks to personnel. The sound level of the vessel’s own signal at listening posts shall not exceed 110 dB(A) and as far as practicable should not exceed 100 dB(A).
(f) A vessel at anchor shall at intervals of not more than one minute ring the bell rapidly for about 5 seconds. In a vessel of 100 metres or more in length the bell shall be sounded in the forepart of the vessel and immediately after the ringing of the bell the gong shall be sounded rapidly for about 5 seconds in the after part of the vessel. A vessel at anchor may in addition sound three blasts in succession, namely one short, one prolonged and one short blast, to give warning of her position and of the possibility of collision to an approaching vessel.
(g) A vessel aground shall give the bell signal and if required the gong signal prescribed in paragraph
(f) of this Rule and shall, in addition, give three separate and distinct strokes on the bell immediately before and after the rapid ringing of the bell. A vessel aground may in addition sound an appropriate whistle signal.
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