How do reflection, refraction, diffraction, and interference affect sound waves?

In the study of acoustics, sound waves are significantly affected by four fundamental physical phenomena:

• Reflection: Sound waves bounce off surfaces, which is essential for reverberation and the acoustics of enclosed spaces like auditoriums. Reflective surfaces can be used to direct sound toward listeners, though improper geometry can lead to echoes or uneven sound distribution.1
• Refraction: This is the change in a wave's direction caused by a change in its speed as it moves through different media or conditions. For example, sound waves travel faster in warm air than in cold air; at night, sound traveling upward can be refracted back toward the ground by warmer upper layers of air, allowing it to be heard over greater distances.2
• Diffraction: This is the ability of sound to bend around obstacles or spread out after passing through an aperture. Because sound wavelengths are often comparable to the size of everyday objects, they diffract readily. Lower frequencies diffract more easily than higher frequencies, which tend to travel in straighter paths.31
• Interference: Based on the principle of superposition, when multiple sound waves overlap, they combine to form a new wave. If they are in phase, they create constructive interference (reinforcement); if they are out of phase, they create destructive interference (cancellation).45