When a "vented" bladed head whistles or makes any noticable "pitchy" sound, it is often due the broadhead being misaligned on the shaft or a blade(s) being slightly bent.
Yep. Getting the head aligned properly is the only cure I know for a whistling broadhead. I don't know anything about a filing trick. Haven't seen anything at all in the forums about it. At least, not that I recall.