This is a simple and relatively cheap solution that still look nice and meet the requirements. The main idea is to build the walls of square pillows, stacked on each other. The special made pillows are build of isolation material as foam rubber etc and than coated with clothing. This will reduce sound from outside effectively. Here is something similar:
http://nerdapproved.com/wp-content/uploads/2009/10/brick-wall-pillow.jpg?cb5e28

These are hold in place by a scaffold made of steel L-bars, either mounted with screws or to be welded together. An alternative material could be aluminium.

A sliding glass door should be available from suppliers in desired dimensions. Here is an example:
http://www.andersenwindows.com/servlet/Satellite/AW/AWProduct/awProductDetail/AWProduct/1137170164332/1102951372828?model=200+Series+Perma-Shield+Gliding+Patio+Doors&pc=Window&tab=1-1

An other concept with this solution could be to have all four walls with pillows but the amount of area space would be reduced though but small furniture's could be a solution.

For virtual effects these models where used:

Chair by: Jaydeep.C
table by: Zeljko Fabijanic
Bar chair by: Maragera
Round Table by: Tobias Mattsson

Sliding door:
http://www.3dcontentcentral.com/secure/download-model.aspx?catalogid=171&id=294213

by: Rob Winckel

With kind regards

Josef Snabb