What are some cheap hacks for noise reduction and/or improving acoustics in rooms?

Cork is the old-school, original way of sound-proofing a room. It's not perfect, but it does do an amazing job. An easy way to use cork for soundproofing is to buy it in rolls or tiles, and then adhering them to the walls. Cork comes in varying thicknesses so just make sure you don't get a cork roll or tiles that are too thin. This is basically the cheap version of something more professional, like this cross-section of a specially built "sandwich panel" comprised of plywood and cork.

The egg packages does not really works, the better is to isolate Sound by using absorbent materials, like floor carpet. Ir you're going to use fiberglass i highly recomend to call a professional as fiberglass is considered to produce cancer if breathed. For the walls You might use some paintings and curtains and loose fabric. Hope This helps someone in the future .

As a longtime music player, we used to insulate our 'studios' (aka house cellars) with egg packages. You know the large ones you find in stores to hold fresh eggs. That was the ultimate do-it-yourself solution. For a business ambient, try to use padding: when possible, cover the surfaces with fabric: felt is best. So, hang felt surfaces on walls, and use rugs and carpets. To separate spaces, use screens: a wooden plate, covered with felt on both sides (you can use also moquette) works miracles.