That year poor acoustics created such severe reverberations that the speakers couldn't help but hear their own echoes as they spoke. Of course Reagan, being the consummate performer, was able to adjust. To ensure speakers are not distracted at this year's convention, workers removed monitor speakers from the stage. Instead they installed smaller speakers on a shelf on the lectern. With this arrangement, on-stage sound will be focused directly at the speakers' faces and not toward the hard wall behind the podium.
Sound occurs when a body, such as a vocal chord, vibrates, or moves back and forth.
Movement in one direction pushes air molecules before it, crowding them together. When it moves back again past its original position and on to the other side, it leaves behind it a nearly empty space. The motion of the shifting air molecules is similar to the motion of a wave through water. That's essentially what would happen here when the sound waves reach the slate backdrop. Greek philosopher Chrysippus, who lived during the 200s B.C., was one of the first to suggest that sound moves through air in a similar way that energy travels through water.