An Acoustic Mirror
Inside the Kok-Gumbaz Mosque in Shahrisabz, an unamplified human voice can fill the vast space. The building is a functional public address system constructed from brick and tile. The scientific principle at work is acoustic reflection, manipulated by the building's precise geometry. The main component is the enormous sphero-conical dome, which has a diameter of 46 meters. Its smooth, curved interior surface is like a parabolic mirror, but for sound waves instead of light.
Sound waves originating from a specific point near the floor—the focal point where an imam would stand to lead prayers—radiate upwards and strike the dome's surface. Instead of scattering, the waves are reflected and redirected downwards to a second focal point in the main prayer hall where the congregation gathers. This effect concentrates the sound energy, allowing speech to be heard clearly without electronic amplification. The hard, reflective interior plaster, known as ganch, minimizes sound absorption and increases the reflection. The building's square main hall and deep wall niches also influence the room's acoustic response, preventing disruptive echoes while preserving clarity.