Why does an empty room echo?

Related questions

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2. What exactly is reverb?
3. What is the difference between delay and echo?
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5. What causes reverberation?
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7. Why we Cannot hear echo in a small room?
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10. Is echo and reverb the same thing?

Tags

1. #furnished
2. #echoes
3. #waves
4. #absorb
5. #reflect
6. #level
7. #louder
8. #hence
9. #empty
10. #furnishings
11. #there
12. #sound
13. #better
14. #convert
15. #unable
16. #because
17. #while
18. #therefore
19. #space
20. #control
21. #filled