On a slightly different but related subject, I live on a boat with a diesel engine. Being able to hear the engine run and hear the change of tone is something I

On a slightly different but related subject, I live on a boat with a diesel engine. Being able to hear the engine run and hear the change of tone is something I couldn't live without. I often run the engine to heat my water and the very slightest change of tone has my ears pricking up, panicking with "I've not heard that sound before! What's up with it? Is it broken? Am I going to sink??" running through my head.