I recently completed sound testing with very sophisticated equipment and an engineering expert in the field. I plan to publish the results once all the data is analyzed, but I can give you my initial assessment. Some broadheads and vanes are louder than others and in general vents in the blades do increase the sound. However, at the location of the animal, the noise level was the nearly same for all broadheads, fletchings, and field points until about .01 seconds before impact. In other words, they don't hear the increased noise from blades or vanes until the arrow is about 1 yard away, so it's too late to react. For a 30 yard shot with a bow speed of 300 fps for instance, it takes the arrow 0.3 seconds to get to the animal. The sound of the bow gets to the animal in about 0.1 seconds, so they do have about 0.2 seconds to react to the sound of the bow. After hearing the sound of the bow, the arrow noise is quite low at the location of the animal until just before impact. I plan to show overlaid sound intensity plots to support this conclusion under the Iron Will Outfitter's thread once completed.
