Noise at 2k rpm

[S3_quattro]

I was driving and noticed a strange noise at 2000 rpm. it was like a small rattle noise from the front of the car. it all so happen when u stop accelerating and decrease rpm to 2000 rpm . can someone help.

 

[AlexStanley]

Something exhaust related, perhaps?

 

[tvr1]

you sure it wasnt pinking as this sounds like a high pitched rattle, low grade fuel ?