A very simple approximation of your voice as it’s heard if you’re facing someone when speaking would be using a unidirectional mic and recording yourself with the mic pointing the opposite direction as it normally would be (in other words— with the polarity reversed).

A slightly better approximation would be if you did the same thing but with two unidirectional mics pointed at slight angles (with the polarity still reversed) to simulate the placement of your ears.

Obviously the quality of the mic would factor in as well—you’d want mics with a flat frequency curve. To get even pickier you’d also want to use headphones or speakers with a flat frequency curve to listen to it. Once you had the recording you could even take impulse responses of certain rooms and process the audio to get an idea of how you sound to others in specific rooms!