I thought the noise, a scraping, sighing sound might have been disc run out

but it is not cyclic i.e it does not happen every wheel rotation.

It does not sound serious, just curious, it may be there all the time and I have

only just noticed it. Short run, aircon on.

Stone stuck in the disc?

Llanigraham, thanks but no, I had grit in a disc before

and as I said it is not cyclic, as in a wheel turning.

Running low on aircon gas?

Undertray hanging off ?

Undertray hanging off ?

No I just went out and looked

 

Running low on aircon gas?

Its cooling ok, gives me freeze head

It seems to be a car speed related thing, with the aircon fan hardly turning then as engine revs rise

the noise goes and the fan turns quietly as normal.

The wife?

Could be, as she drags my small change across the table (scraping) and realises just how little money I have (sighing)

at low speed (to avoid waking me)

Edited 21 August, 201411 yr by gumdrop

My old 110 TDi made this noise intermittently from new. I took it in to the supplying dealer and the tech who took a listen told me it was either an "induction noise" or possibly related to the EGR system, and of no consequence. He said it was especially common on the CR and mentioned his vRS Octavia did it also. At the time I did wonder if it related to either the clutch or fly wheel, but as you have noted it doesn't seem to relate directly to engine revs. The car ran to 40k miles with no engine related issues (just rusty doors) and made the noise intermittently throughout. I've now moved on to a 140 TDi manual and have yet to hear the noise.

Thanks pinkpanther, the most likely reason yet.

I just remembered that I posted a sound clip of the noise my old car made - here: http://www.briskoda.net/forums/topic/268757-new-strange-noise-from-diesel-yeti/