wierd sound from front end

[jimpomm]

I have a friend with a 2000 legacy that dropped by today to ask about a noise in the front end.when going straight ahead no noise,when turning at about 15 miles per hr or more to right or left there is a whoop ,whoop noise that kind of sound like something rubbing on the backing plate for the brakes .There is no change in the noise when brakes are applyied when turning so I dont think it is brake related.Any ideas on what this is and what to do about it .?Thanks Jim