High capacity PoE switches inherently need substantial airflow due to power density. The fans are thermostatically monitored. Speed (and thus noise) will vary depending on internal temperature and load. The fans should come on very strong on power-up and then slow down after the switch fully boots up, but in warm environments or if there is high PoE usage the fans will increase speed to allow proper cooling.
Have you flashed the switch to the latest firmware? Some early switches had an issue with the fan speed being always at maximum and a firmware upgrade fixed it.
I would strongly discourage exchanging the fans for a lower speed or lower CFM version. This could result in the switch overheating and failing which wouldn't be covered under warranty. The long-term solution may require relocating the switch to a server room or data closet (with proper ventilation and A/C) and out of an office environment.
