True variable speed settings allow for precise airflow control
I don’t know about you, but I think most fans run too fast, even on their low-speed setting. I generally like to have a little air moving around, but your standard desk or floor fan moves around too much air and makes too much noise for many situations. If you are getting a new fan, then one with infinitely variable speed control built-in might be the ticket. I have a Vornado fan
with that feature that I like quite a bit.
When on low speeds, it is very quiet, and at high speeds, it moves a lot of air. However, it is pretty pricey compared to most fans, especially one you already own.
For existing fans, you may be able to use a speed controller to get more common fans to run slower. I got a KB Electronics Solid State Variable Speed AC Electric Motor Control
and with that, plus an electrical box, an extension cord, and a couple of wire nuts, made a fan speed controller that works great with a small desk fan. I can turn it down low enough to where it is essentially silent, and still get enough air to keep cool. Please only try this if you know what you are doing. If you use this speed controller with the wrong kind of motor, or if you use an underrated speed controller, bad things could happen. From what I’ve read, this controller will work with the motors typically found in inexpensive box fans, oscillating fans, etc. But please research it for yourself.