I had the vented hood professionally installed. The HVAC guy followed the instructions, and used the recommended type of ductwork, and the vent was straight thru the wall to the outside.  The result is that the vented hood is really quiet even at high speed, and it works beautifully to vent all the cooking smells outside.  I like the lighting too.  I always wanted a hood that was vented to the outside, and I just love it.