I would say it could still go either way. I had one this year that I swear was making a quack sound but still turned out to be a male. I think they do have a sort of different transition sound for a few days before they get their man voices.Also... do we think boy or girl? Doesn't sound like the beginnings of girly honks to me, at least not how I remember. But I don't remember the boys' voices cracking like that... seemed like they just subtly transitioned from peeping to their raspy quiet quack, and later on, I thought - like around 7-8 weeks old. Where the girls started honking anywhere from 3-6 weeks... baby duck was 5 weeks old yesterday. It's been 4+ years since I had baby ducks around though, so my memory might be off.
P. S. This was our first try at letting baby duck spend some time outside safely. He/she was not amused at all at first, but eventually nibbled on some grass and sat down and enjoyed it. I may try it again out back with the big ducks in the next day or two.