Are the dimmers rated for CFL bulbs? When you say "they both buzz", do you mean the switches buzz?

Yes both switches for the same light buzz, on is dimmer the other one is a rocker switch.

I can't really answer why the switches buzz, but I can make two comments: I would be most worried why regular incandescent lamps burn out regularly - overvoltge? If the dimmers are as old as the house, they are probably not meant for CFLs. I have had dimmers make the lights buzz, but not the dimmer.

1. Here's an article on the subject: https://www.thespruce.com/why-switches-make-buzzing-sounds-1152821
2. I'd replace the switch. Be sure to buy a 3-way switch.
3. Most CFLs are not dimmable. Check the label on the bulb.

• If you want to use a non-dimmable bulbs, replace the dimmer with a second 3-way switch.
• If you want dimmable lights, replace the CFLs with dimmable LEDs and replace the dimmer with a 3-way dimmer that supports LEDs.