Rackspace did a similar thing in San Antonio. There are many photos of the transition here: https://www.mysanantonio.com/lifestyle/slideshow/Photos-show...
The noise was crazy. Even after taking steps to address the noise it was still an issue. Not much you can do with all the concrete a mall is typically made of.
And the 2nd floor shook and moved around a lot after folks moved in. It was actually nauseating.
IME, the effort needed to reduce unwanted noise depends a lot on the frequency range.
Very roughly speaking, dampening high-frequency sounds can be done with relatively thin and light sound-absorbing materials. Lower-frequency noise, including vibrations that shake the building's superstructure, require more extensive modifications.
It would be awesome if an actual acoustic engineer or architect could weigh in on this.