This project is fascinating:

“while moving through the installation - built-in microphones pick up the sound of the visitors and a computer sound system filters 

and remixes the recorded pitch and sends it to built-in electrodynamic resonators. here, the project becomes an instrument and plays 
a constantly changing soundtrack. the work acts as an archive of noise while the users’ understanding of space and presence is amplified.”

http://www.designboom.com/weblog/cat/30/view/24305/thilo-frank-ekko-spatial-installation.html