hello...i have a 2006 a4 2.0T...sweet ride

i noticed today when i stop on a hill facing DOWN with the car in REVERSE and my foot on the brake (and engine running), there is a faint high pitched tone...the tone stops when i take my foot off the brake and hit the gas...

same tone when i stop on a hill facing UP with the car in DRIVE and my foot on the brake...the tone also stops when i take my foot off the brake and hit the gas...

the hill does not have to be steep for this sound to start...there is no sound when i'm stopped on flat road...

is this a safety feature?

thanks...

 

is it the auto hill stop, i kno the passat has it

 

what is auto hill stop?

 

edit:
Hill hold Assist
and u need to push a botton to activate and i dont kno is the A4 has it so im so off