As you decrease the area of the opening, the velocity of the air flow increases and usually results in more sound/noise. As you increase the area of the opening, velocity decreases and usually results in less sound/noise. In theory, there will be an opening large enough to negate any suction but also in theory, there should be some optimal size opening that will give you acceptable suction with acceptable sound/noise. I think we all know that 3/4" is not that optimal size so please report back to use as you increase your nozzle size.