If you have a fairly recent iPhone or iPad that supports Apple's Spatial Audio feature – there's a full list of supported models here – or a Mac running macOS Monterey there's a semi-secret system setting that can make your voice sound much clearer in voice and video calls.
The FaceTime feature is called Voice Isolation and you can access it by opening Control Centre during a FaceTime call. If you tap on Mic Mode you should then see the image above, which has three options: Standard, Voice Isolation and Wide Spectrum. Standard is the default.
If you select Voice Isolation, your iPhone or iPad will start to process the audio to remove sounds that aren't your voice. It can reduce or even silence ambient noise in much the same way that noise cancelling earbuds do, making your voice much easier to hear. If you want the opposite and would like people to hear all the sounds around you as well as your voice, tap on Wide Spectrum instead.
FaceTime voice isolation: the pros and the cons
The benefit of voice isolation is pretty clear: you're easier to hear, and there's much less echo too. But there's a downside to that, which is that your voice sounds more processed than it would otherwise be. That's not going to be a big deal for making calls but if you're using FaceTime for podcast recording or other applications where sound quality matters then the processing might be a little too much. We're hardly talking T-Pain-style AutoTune here, but it is noticeable.
For me, I think the benefits outweigh the downsides: it's really nice to hear people without also hearing them tapping away on keyboards. But while it's a useful feature it could be implemented better: it's available in some other apps such as WhatsApp and Snapchat but not TikTok, it's on Zoom mobile but not on Zoom for the Mac, and it isn't available for normal phone calls. And if you find the feature useful, you'll probably be irritated that you can't set it as the default: you'll need to enable it manually in every single conversation. Hopefully Apple has noticed the amount of attention this feature is getting and will improve it in future versions of iOS.