Most parishes I have been to today, play Gregorian chant or have a fan or something going outside the confessional door. Many years ago I remember being at different parishes where people tended to congregate to closely in a line outside the door waiting for confession (jockeying to hold their position, I suppose). Some of the confessionals only had a curtain.
We had one visiting elderly priest who couldn’t hear very well, and would encourage people to speak louder, which is the last thing I would want to do in a confession with others outside the door.
If you can hear what is being said the polite thing to do would be to move back further.