Which bird is famous for mimicking human speech?

Parrots, and they do it without anything resembling our equipment. A parrot has no vocal cords. It shapes sound in the syrinx, a structure at the fork of the windpipe that birds have instead of a larynx, and uses its remarkably muscular tongue to form the result into something that lands on a human ear as words.

Whether it means anything was a serious research question rather than a rhetorical one. Alex, an African grey studied by Irene Pepperberg for thirty years, could identify colours, shapes, materials and quantities, answer questions about which of two objects was larger, and grasp the concept of none. He was not reciting; he was asked novel questions and got them right.

In the wild the ability is social. Parrots live in large flocks with dialects, and mimicry is how membership is signalled - wild parrots appear to give their chicks something like individual names. A bird kept alone treats its household as the flock, which is why it learns the phone ringing and the microwave as readily as speech, and why an isolated parrot is a welfare problem rather than a novelty.