Try clapping inside the Golconda Fort and discover what happens.
Snap your fingers and you shall be heard a distance away. The first thing anyone entering the Golconda Fort in Hyderabad does is clap. No, they are not seeking the help of the king, they are testing the acoustics of the Golconda Fort from where the Qutb Shahi kings ruled for nearly 200 years. Clap inside the grand portico under the dome and it can be heard in the Bala Hisar pavilion more than a km away, on top of a mountain. Even today, as buses and vehicles roar around the inner fort, you can hear people clapping in the portico.This story is not about the acoustics of the Golconda fort but about exchange of technology much before broadband, Internet and computers made this possible with a click.
The fort that used to be a rock and mud structure was completed in 1582 under the supervision of architects, most of whom hailed from Isfahan in Iran. Mir Momin laid out the plan for Hyderabad with Charminar at the centrepiece. As you clap, try noticing the series of arches with diminishing sizes. The arches are one of the secrets of the stunning acoustics that could help an army commander listen to what the sentry was doing.A similar acoustic device can be found in Isfahan where it was created for religious purposes.
The Shahi Mosque (now called Imam Mosque) has twin echo chambers that ensure that the Moulvi in the tower can be sure of being heard by all the congregation when he gives the sermon. In the middle of the great prayer hall there are few black paving stones. Stamp on them and it creates seven clear echoes.
These ancient architects understood both the facets of sound echo as well as amplification that form part of sound physics. They used material known for their sound reflection properties like clay pots and pans and blended them into the building material. The next thing they did was use compression and amplification. The architects did not bring maps. They just understood sound. The clapping portico in Golconda Fort has on one side a series of arches, each smaller than the preceding one. So, a sound wave generated under the dome of the portico would get compressed and then bounce back amplified enough to reach a distance of more than a kilometre.