'99 Volvo V70 XC AWD making high pitched siren noise

I have a '99 Volvo V70 XC AWD that is making a high pitched whine that sounds kind of like a siren at times. Usually goes away if I’m driving at high speed on the highway. It’s more pronounced during in-town driving on acceleration/deceleration. Turbo?

Hope not the turbo. Hope for the best–maybe a belt or belt tensioner or pulley? Can you hear it at idle? If so, try to determine which part of the engine it is coming from.

Can’t hear it on idle. I’m wondering if I should change the transmission fluid.

Well, you should change it every 30,000 miles or so but it probably will not help at this point. How does the fluid look? (level, color, smell, etc.)