Spanish to English Other Ships, Sailing, Maritime sonido

This is a deposition by a Mexican ship's mechanic related to a tourist vessel accident. He is describing all the systems and equipment he checked before telling the captain everything was OK. My question is, what does "sonido" refer to? Is he talking about a sound/communication system on the tourist boat, or is it possibly a sounding system that would tell them the distance to the bottom of the sea? Several times later on in the deposition, there are references to being "sin el sonido", but it still isn't clear whether they are talking about the ability to communicate with passengers and crew, or the ability to know they were about to run aground. Many thanks in advance!