The best way to spray an acoustic ceiling is by using a hopper. You should also use a ladder and wear a respirator. First, cut the hole in the ceiling, then attach the hopper to the opening. Next, fill the hopper with insulation and turn it on. Finally, use the ladder to reach the top of the ceiling and spray it with insulation.

You can't just go to the store and buy a can of acoustic ceiling spray. It's not that kind of product. You have to hire a professional to do the job for you. They'll use a commercial-grade sprayer to apply a thin layer of sound-deadening insulation material to the surface of your acoustic ceiling. The most common type of acoustic ceiling is made from fiberglass, so the insulation material will probably be some type of fiberglass too. It's important that the material is applied in a very thin layer, or it will just make the noise problem worse. That's why it's best to leave it up to the professionals.