I can hear my montecs in flight, but they are no worse than some of the other fixed blade heads I have used in the past.

Depending on what year montecs you were shooting, some may be louder than others.
At least that I am aware of, there are 3 versions of the Montec heads

Ver 1) Non tapered blade vents and non tapered rear on the blades
Ver 2) Tapered blade vents and non tapered rear on the blades
Ver 3) Tapered blade vents and tapered rear on the blades

I have some of all 3 and the Ver 1 heads are the loudest, with Ver 3 being the quietest.

In any case, other than a spooky Texas whitetail, I have never had a deer that seemed to react to the hiss of the arrow, just the sound of the bow going off.