Wa Wa sound?

[oldsub86]

My truck has had a problem for quite a while and I occasionally think about it but have not done anything much about it to date. At slow speeds there is a wa wa sound. I think it comes from the front wheels and it sounds like increases with the speed of the wheels. I suspect that it is probably still there at higher speeds but no longer discernable because the truck is noisy. The truck is bone stock in the sense of wheels, brakes etc so still drums.
I know I haven't given you much to go on but I wondered if anyone else has encountered a similar sound and tracked down the source of the noise.