it sounds like a front pump gear whine . if the oil levels are good and your not finding any metal in the samples then keep on driving unless you want to take it apart and try swapping in a new or different front pump
...PM me for advice or service questions.
1988 S4 Elfenbein Perlglanz/Pearl Gray leather , Auto, X pipe
1985 Euro Auto, Blue /Blue, Swiss Sleigh Trans
1985 Euro Auto, Brown, Black 5.0 block
1985 Euro 5 speed Blue/majestic , Samanthas
1986.5 Auto, Meteor /Tan 2.0
1982 Wessach #13 auto.
1985 Euro 5 speed Big brakes Black/Black 16V
1986 5 speed Mossgruen/Brown
1986.5 Auto Meteor met /Tan 1.0
1984 Euro Auto, Grand Prix white/ Tan