Sometimes when I play I get this certain whistle as if something is between the bowand the string and totally throws off the sound. It will either whistle, or dull the sound. Any suggestions as to what causes this and how to prevent it.
One reason may be my begginer violin, a Florea outfit.

Hi,

This whistle sound can sometimes be caused by a badly fitted bridge. If a string (often the "E" string is too close to the fret board it will squeek away. Chech the bridge. Do the strings touch the fingerboard near the nut when viewing the fingerboard from the side. If so a quick and easy remedy is to get a tiny piece of leather and place it on the brige for the offending string to sit on.
The other common whistle can be caused when we play the violin. If your hand (not bow hand) clips the strings when you play then the note dosent sound.

Hope this helps