Answer: Excessive reverberations take place
Notes: When we shout in an empty hall, we hear your own sound after a short time. This is because the empty room reflects the sound, so there is an echo. When a hall is full of people, the sound produced is reflected multiple times by the people. This causes the sound to overlap with the original sound, so the listener can't distinguish between the two. For an echo to be heard, the surfaces need to reflect the sound, or there needs to be more clarity. For example, big open spaces are good for hearing echoes.
