How do curved walls and domes create unwanted echoes in auditoriums?

In architectural acoustics, smooth, curved surfaces such as domes and curved walls act as focusing elements for sound waves. Because sound follows the same law of reflection as light, these shapes can concentrate sound energy into specific areas rather than diffusing it evenly throughout the space.12

When sound is focused in this manner, it creates large, undesirable echoes and poor sound texture. This effect is particularly problematic when sound from one part of a performance is concentrated onto a single section of the audience, leading to an improper blend of sound. In extreme cases, such as in elliptical domes, the geometry can create focal points that function like a whispering chamber, where sound is intensely focused from one point to another.12

To prevent these issues, designers typically avoid smooth, curved shapes in auditoriums or cover them with sound-absorbent materials to minimize reflections.13