Poorly designed auditoriums can have dead spots. Dead spots are places where destructive interference occurs from the interaction of two or more sound waves. For example, a soloist on stage sends sound waves into the audience. Some of the waves hit the walls of the auditorium, while other waves travel directly to the listeners. In some situations, a direct wave can destructively interfere with a reflected wave so they cancel each other out at that particular location. As a result, the listeners seated in those particular seats would hear nothing from that soloist. Someone sitting a few seats over from the dead spot, however, might not experience the destructive interference and would hear the soloist just fine. (Refer to the chapter on Sound for handy answers dealing with acoustical engineering.)