In fact, it was given only to junior-level employees, not to the biggest executives and top developers.

Huh, the vimeo one is weird. I'd think we wouldn't be able to hear them talk, let alone move boxes (at around the 1:00 mark).

Of course you can hear sounds: but you can only hear direct sounds. All reflected sounds are gone. And that's actually a high percentage of the sounds you normally hear.

An anechoic chamber is used to test acoustics in an environment with absolutely no reflection (reverb, echo, etc.).

Not to mention the ventilator, the HDD, and the rest of the electronic components.