Just in case someone else reads this and is confused, I'd like to clarify the matter of fan sizes and noises. As one of the previous posters has stated, and as the overwhelming majority of the posters here will confirm, smaller fans are louder for a given amount of airflow. Someone may have a loud large fan and a quiet small fan, but that's going to occur because the loud fan is older or just imperfectly manufactured (or just cheap), or because it's a normal large fan compared to a high quality small fan. As a former technician with over a decade of experience, I have seen it over and over again - larger fans, all things being equal, tend to push more air and, at the same time, produce less noise than smaller fans.
In the end, though, good design trumps everything else. A small fan placed well can be quieter and more effective than a large fan in a less optimal position