I'm not sure whether you're talking about "whistle" or "hiss". To me, you whistle when you call your dog. A broadhead should not whistle. I have had some 4 blades of various makes whistle, and putting a little chap stick or string wax in the bleeder slot in front of the bleeder made it disappear.
Hiss on the other hand is normal for some heads (like Snuffers) and should not be any cause for concern IMO. Perfect alignment and a little practice shooting, which can help to clean up any rough edges will help to minimize hiss.