“Use ambient noise reduction”.

It will depend of what Mac model you are using and the Audio Input:

Capture less background noise when using your computer’s built-in microphone:

Select “Use ambient noise reduction.” This option does not appear if a 4-channel built-in microphone format is selected in Audio MIDI Setup or on Mac models with an Apple T2 chip.

Change the sound input settings on Mac - Apple Support

Hope this helps and solves your question. Do not hesitate to ask if you need more information.

I can't be sure but most people is complaining about "Use ambient noise reduction" it's gone since MacOS Catalina, but because they want to have it turned off ) saying it's permanently on.

Regarding plugins I'm not using any to give you a good recommendation.

Head to Menu » About this Mac » System Report » Controller

Should show the T2 model name if you Mac have it.

Mac models with the Apple T2 Security Chip - Apple Support

I don't have a T2 chip and the built in mic has 1 channel, but I still don't see the option. (Big Sur 11.2.3 (20D91))