Rumbling sound

[trisager]

Currently flying the turbocharged version. In the cruise, there is a persistent low-frequency rumbling sound. It is most noticeable with headphone noise cancellation active, but it is still there when I turn noise cancellation off.

I'm assuming it is intentional, but where is it coming from? The airframe itself?

[Black Square]

I think I would need a video to know exactly what you're asking about. Unless it's something really unusual, then I suspect it's just part of the wind or engine noise.

EDIT: Or it could be the tip-tank transfer pumps, if you had those running.

[trisager]

After a bit of experimentation, I think it's the engine noise. I suppose the noise cancelling headphone simulation works by reducing the higher frequency components, making the rumble more noticeable.