Foghorn

A foghorn was a sound signal used to alert boats to the presence of danger. The Fang Rock lighthouse was equipped with one. Reuben asked the Fourth Doctor to keep it sounding when the island was engulfed in fog, but he delegated the task to Leela, who found pleasure in its use. (TV: Horror of Fang Rock)

Leela enjoys playing with a foghorn. (TV: Horror of Fang Rock)