How to sound-proof large spaces?

We are organizing a conference and we want to cut off a section of a large room to create a separate room. However we want the partition to be sound proof. The ceiling is tall (over 20 feet) & exposed.

The length of the partition needs to be over 75 ft

How much sound deadening do you want?
One solution is to build a metal frame and Sheetrock wall all the way to the ceiling with insulation in the center. If you want more sound deadening then put 1/2" sound board on each side of the metal frame and then put the sheetrock over it.

You can also increase the insulation area and thickness inside the wall by using a 6" metal frame instead of a 3 5/8" frame or a 4" frame. A 6" wall with R30 insulation and 1/2" soundboard on each side with 5/8" sheetrock over that should be a very effective sound barrier.

The next option would be to build two parallel 3 5/8" walls with a layer of soundboard sandwiched in the middle and then a layer of soundboard on each side with insulation inside the walls and then the sheetrock over that.

Call a local commercial drywall company and give them my above recommendations. They will know what to do. Don't call a house builder for the job, because most will not have a clue.

PS: Install the soundboard horizontally and the sheetrock vertically.