I have never heard of the term 'Noise short' I would go for option 'b' It could refer to a noise transmission path through the solid body of a material, that is unintended because 2 items of equipment have come into contact with each other, when they are usually physically separated.

Fox, As an ex Submariner the term "Noise Short" fits exactly with answer B. However, I don't see it's connection to H&S noise. To me a noise short is a "defect" whereby an isolated piece of machinery, such as the main engine raft is accidentally connected directly to the hull by either a non flexible section of pipe or by for example a spanner wedged between the hull and the raft. Main engines and other loud machinery are mounted so as to acoustically isolate the source of the noise from the hull. The time and effort that goes into identifying and eliminating noise shorts is huge as it gives the boat a massive advantage in combat as the primary source of information for tracking / targetting other submarines and ships is the noise signature, which is unique to each hull..... In the "Silent Service" Silence is Golden Jim

Thanks to Fox for posing the question and also to ExDeeps for his helpful and interesting answer because it's likely that most forum users had, like me, never heard of 'noise short' before seeing this thread. As noise and vibration are often interlinked, there might even be related expressions like 'vibration-short' or even 'noise-vibration short'. Even so, it remains a bit of a mystery as to why the question was posed in the examination paper described. ExDeeps' comments about submarine noise and signatures might 'ring a bell' (in keeping with this thread’s accoustic theme) with those who watched the TV programme last night on the ‘Yesterday’ channel about submarine warfare during WW2. They’re also a reminder about the scene from the film “The Cruel Sea” (1953) when the Royal Navy ship had to stop at sea for noisy but crucial repairs to its engines and the captain asked the engineers to try to keep the hammering to a minimum. As he put it, he was concerned that U-boats would appear from everywhere to complain about the noise!

I contacted my son - Senior Design Engineer on the next generation submarines. He confirms its a common term in his line of work and that 'Deeps nailed it.