Final answer:
Dead spots in a concert hall are created by the interference of sound waves, which can lead to areas with dull sound or excessively loud sound, influenced by the hall's acoustics, geometry, and materials.
Step-by-step explanation:
Dead spots in a concert hall can occur due to the acoustics of the room. Sound waves can interfere with each other, leading to areas where they cancel each other out, causing dead spots where the sound seems dull. Similarly, constructive interference can result in areas where sound seems excessively loud. This is because of the complex way that sound waves can reflect off walls, ceilings, and other surfaces, and how they can interact with the specific geometry and materials of the concert hall.