>>11441868The more engineers try to advance robots, the more they end up just mimicking the human body. Walking for example, is humans using momentum and swinging to move their legs rather than using all the legs muscles to lift the leg up, move it forward, then set it down. It is more natural looking and efficient to do it that way and now engineers are designing robot walking with that in mind. So if you are looking a more natural voice, how about making a voice box with valves that you can control in order to make the air that passes through the voice box produce a sound? You will need a tongue and mouth as well to shape the sound, and all of it needs to fit in a small space. This is harder than it sounds, probably harder than getting a robot to walk and that took 40 years to do. I think one of the main hurdles is we lack the materials. We are still using hydraulics and servos for much of robotics, we something with much more flexibility and elasticity to move the mouth and tongue. Until then, you are just going to have to use improved speakers.