I enjoyed this recent article in the New York Times about the weird experience of being in an anechoic chamber—a special room that absorbs absolutely all the sound around you.
Legends tell of an echoless chamber in an old Minneapolis recording studio that drives visitors insane. I figured I'd give it a whirl.
I remember spending some time in one while I worked at Mattel Toys. They were the leading proponent and developer of mechanical voice toys. You know: pull the string and hear Chatty Cathy say 11 things! Although Edison invented the talking doll, it was Mattel in the 60's who really perfected the concept of spring powered, miniature record players with all mechanical (no electronics) playback. That relied on nylon records with "hill-and-dale" grooves, whose up-and-down shape provided the mechanical punch to make loud and clear sounds without an amplifier. For best sound quality they had to be EQ'ed just right and that included an advanced audio lab with an anechoic chamber.
As described in the article, being in one was a very weird experience, kind of like being in a sonic black hole. Without any echoes to sense locations, sounds or voices seemed to be inside your head. You'd hear your own heartbeat and breathing. Working on sound toys was fun but this was weird. Oddly both disconnected and claustrophobic!