Answer to Question #21702 in Acoustics for Anita Sharma

Question

Sound waves get reflected so that they superimpose each and resonance occur. Also sound waves are absorbed so that echo is not heard in crowded hall (although it is heard if hall is empty). And in open organ pipe resonance occur because it encounter with free air outside the tube and reflects back. My question is, if air can reflect the sound wave, how can we hear sound? And what are the conditions when sound waves get reflected or absorbed?