Unfortunately, that is so vague it can be just about anything. Does it occur during accleleration? It could be the CV joints on the transmission or the transmission itself. Does it happen during braking then it could be something to do with the brakes. Does it happen while you are crusing with no acceleration? Then it might having something to do with the suspension.
With increasing speed does it get faster? If so, it might be something caught in the wheels or the brake pads are worn so the "whistle" warning may be telling you the pads are near worn out is exposed.
Your comment is so vague no one can even hazzard a guess on what it is . Either give more information or don't expect a useful answer.
Best of luck.