Very likely if the noise is still there after you put Velcro on the limb, then the noise is coming from where the limbs attach to the riser, as Henry said. The primary place I have found this is in the alignment pin, because there is usually some movement of the limbs when the bow is drawn causing the pin to slide a little bit in the hole. You might try putting some Vaseline or something on the pin and see if this eliminates the noise. If it does, it won't be permanent, but at least you'll know where the noise is coming from. Hopefully, over time, the pin and the hole will wear in and the noise will go away permanently.
With the exception of Rick Welch Dakota bows, which come with Velcro on the limbs, most bowyers recommend not putting Velcro on the limbs. I don't know why, but I know they don't like it.