During construction of all our new homes we install Panasonic Whisper Green Bath Fans. Panasonic bath fans are extremely quiet, so much that people don't notice the fans running.
Panasonic bath fans automatically adjust the fan speed to the control the moisture levels in the bathroom. Panasonic Whisper Green Bath Fans will start operating at low speeds and increase speeds when necessary reducing energy usage unlike bath fans which only operate at one speed.
In each bathroom we set the bath fans starting operating speed based on the size of the room, and how much moisture will be produced in the room. If the bath fan would ever need to adjusted for higher or lower starting operating speeds that can be easily accomplished by adjusting the fans settings.