Fan Speed Control

The one I had did make noise, and I have heard others mention the ringing noise from the pulses, so might not be a bedtime item...

I'll touch on this: All PWM controllers have a fixed operating, or switching frequency. Let's say it's operating frequency is 1000 Hz. At that speed it will turn on and off every millisecond. The time period it is on during that millisecond is called duty cycle. At half speed (50% duty cycle) the fan has current flowing through it (turned on) for.5 milliseconds and no current flowing through it (turned off) for .5 milliseconds. At 3/4 speed (75% duty cycle) the fan has current flowing through it (turned on) for.75 milliseconds and no current flowing through it (turned off) for .25 milliseconds.

The noise you hear often comes from the fan turning on at a too low switching frequency. The human ear can normally hear from about 20hz-15khz. I can't hear anything above 8kHz because I'm old. Some controllers will have a switching frequency from 500Hz to 10kHz. You can hear that. A better controller for a fan or motor will have a switching frequency of 20kHz or higher, above the human hearing range. That's why I said the one you found on EBay SHOULD not be noisy because it operates at 25kHz.

However, we are dealing with a mechanical device, the fan. Its blades may not be balanced, bearings may be loose, may not be aligned, etc...
When you change its speed you may fall into a resonant frequency to where it just starts vibrating to the point of making noise. This is not a result of the controller, it's the fan not operating smoothly at a certain speed. It would be hard to overcome that.

Sorry for carrying on but again, I hope this helps you understand what's under the PWM controllers hood.