Loud MacBook fan ruining my audio in meetings. Help?

I'm assuming that you're using the internal microphone on your laptop, which is relatively close to the fan.

You need a microphone that is closer to your mouth than the fan.

To prevent microphone feedback, you'll probably also need headphones.

Many people use headsets with microphones for exactly these reasons. There are plenty of great bluetooth and wired options out there.

What model?

How long's it been happening?

What apps are running?

Have you blown it out recently?

How is it positioned?

Clean out any dust then kill the app that's hogging your CPU.

What software do you use for meetings?

If you have a newer macOS version on an entry Intel machine, ordinary tasks can cause a lot of fan noise. You can activate Low Power Mode [1] to reduce clock speed and therefore the fan will not be as loud. See if the reduced clock speed does not interfere with your daily tasks.

[1] https://www.howtogeek.com/771767/how-to-enable-low-power-mod...