I've noticed a new noise today, one I haven't noticed before whilst driving and it's bugging me as to what it may be.

Basically I have a 2.0tdi (140) that as per when you drive it under load you can hear the turbo. And so when you let off the accelerator you hear the turbo noise drop off which is normal. BUT today I've noticed what I can only describe as an echo of the turbo sound as you let off the throttle. You hear the turbo sound drop then a split second later it's like you hear it again even though my foot is still off the accelerator pedal.

Can anyone shed any light on this for me please? I've definitely never noticed anything like it before.