Does the noise sound like a growl? Hens can growl when upset. It looks like a hen from the picture. But, that is just a guess. Still, I would think that at almost 3 months it would have started to crow.
Cockerel feathers are longer than a hens and can be curly and are usually more colorful. Roosters tend to feather out tail feathers first, hens back and wing feathers.
My missexed rooster started crowing at about 7 weeks and was so much bigger than our hen. His tail feathers were curly and bright and came in way before the rest of his feathers. Also, his comb grew in fast and it was much bigger. Yet, large combs don't always mean rooster. I had a hen with a large comb that came in about 12 weeks.
Perhaps, some of the more experienced members would have an idea.
DB