In my experience, I can still hear some weather when the Muse is registering neutral. I have to go all the way down into calm before the weather disappears entirely.
I think it’s wrong to try to relax and be calm while the Muse is calibrating. This will set the bar too high. While calibrating, the user should have an active mind. This was what the Muse company advised for previous versions of the Muse headband. But now the instructions seem to advise a more relaxed or at least neutral mind for calibrating.
What I do during calibrating is count to ten (in my mind) in English, then in French, then in Spanish, in Russian and finish up with German if I have time. I thought this would keep my mind very active jumping from language to language! But anything that needs an active mind should work well, such as going through the multiplication tables.
Keeping the mind active during calibration seems to give a better range of results when I meditate during Muse. Yes, I do hear the birds more easily - sometimes within 10 seconds of starting meditation - and can stay in the calm zone longer. If you set the bar too high during calibration, it can give frustrating results. You’ll have to try too hard, which in itself can have a negative effect on the results.
I guess if you get really good at the Muse and want more of a challenge, you can start focusing on your breath and calming yourself during calibration, or even before it.