Make up your mind Google AI. Is sound faster in air that is less dense or more dense?
Honestly, there is so much wrong in the AI answers that it’s hard to know where to start, but the direct contradiction of itself seems like a good start.
Sound is usually mitigated not by choosing materials that absorb it when it travels through them, but by isolating parts of the building.
Also Eg. Resonances are a problem. Placing furniture and geometric shapes in rooms is so much easier than say putting it underwater ;) much more practical, too.
Sound usually carries quite far so increasing the speed of sound doesn’t do a whole lot. Might work decent for high frequency noise but that’s not really a thing that is done.
The other commenter provided the formula for the speed of sound in an ideal gas. Please refer to that.