Why do empty rooms sound hollow

Every empty room has echo, it's material does that. The object in the room take away that echo.

Explanation:

An empty room has nothing but hard walls. We know that hard substances reflects the sound . If the distance between you and walls is 17 meter than the sound will echo but if the distance is less than 17 meter than the sound will reverberate . So the empty room sounds hollow.

scientific laws are the result of testing theories and proving them to be facts.

energy can be converted from one form to another, but it cannot be created or destroyed in ordinary chemical or physical means. do not understand what you are asking but hope this