Why do rooms echo when empty?

Related questions

1. Why echo test is required?
2. How does echo occur?
3. Is it rude to whisper in front of someone?
4. What causes an echo?
5. What does an echo mean?
6. What is a soundproof booth?
7. What is a whisper room?
8. What is echo method?
9. What causes echo in a room?
10. What is an echo study?

Tags

1. #control
2. #reflected
3. #nothing
4. #waves
5. #level
6. #space
7. #while
8. #energy
9. #echoes
10. #sound
11. #absorb
12. #empty
13. #better
14. #filled
15. #unable
16. #convert
17. #stands
18. #furnishings