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Whispering gallery, no shouting here

Having set out on yet another local road-trip with old buddies during my visit home this year, we had decided to deviate from the usual routes which were all designed to make Gokarna as the primary destination while the rest of the trip shaped up around it. Instead, we planned to adopt a more northerly bearing considering our long-yearning-and-yet-unsatisfied desires to see historical architectural marvels. This new route promised quite a few prominent tourist attractions on our itinerary – the 1500 years-old majestic cave temples of Badami & Aihole, the stone temples of Pattadakal brimming with Dravidian style architecture and the Deccan style architecture visible in the numerous pre-British-rule era monuments in Bijapur. You may seek details of most of the other places mentioned with the links provided. My focus here is on the apparently simple looking yet enticing 400 year old Gol Gumbaz in Bijapur. The focus of my research, although not entirely relevant, enables me to appreciate the impressive acoustic properties of this mega-structure.

Gol Gumbaz

Gol Gumbaz, viewed from Southwest

The mausoleum of Muhammad Adil Shah, a 17th century ruler, is called by different (but similar-sounding) names in different languages with the most widely used name being Gol Gumbaz. It is a monumental architectural feat given that the modern engineering processes and machinery were unavailable at the time of its construction. Specifics of the structure along with a brief historical perspective can be found on the Archaeological Survey of India’s (ASI) website (here). My intention is not to reproduce the data available on the ASI website or on wikipedia. Instead, I provide information which may not be available elsewhere and which would be handy when you plan your next trip to Bijapur.

Monument details

Description posted at the site

We went to the site early-ish on a weekday hoping to avoid any crowd. Footwear is not allowed inside the mausoleum and there is a convenient facility right beside the entrance for the purpose. Be sure to notice the delicate artwork on the exterior walls while you are at it. When we entered the massive building, I wasn’t surprised to not find any rooms or chambers. Its simply a gigantic hall on the inside with dummy tombs of the ruler, his family members, and of Rambhavati who was a dancer in the ruler’s court. The actual tombs are placed straight below (~16ft) the dummies in a cellar chamber below the hall. Once in the hall, you will be tempted to immediately test one of its acoustic properties. Clap or whistle aloud and try to count up to ten or more echoes. It is said that several decades ago, one could hear a lot more echoes of any sound. The maintenance work carried out over the years in attempts to protect the monument’s surfaces are to be blamed for the attenuation. The monument does not have any electrical lighting. The only light available inside is the dull ambient illumination resulting from inner-surface reflections of sunlight seeping through the entrances and a handful of small windows. Access to the whispering gallery, which is ~50m above the ground and lies along the inner circumference at the bottom of the dome, is available via highly inclined narrow stairs running through the seven-storeyed octagonal towers at the corners of the cubic base. Visitors with low fitness levels must be prepared to sweat it out at the stairs.

Whispering Gallery. Red arrow overlay pointing to my friend on the other side.

Whispering Gallery. Red arrow overlay pointing to my friend on the other side.

To me, the whispering gallery turned out to be the prime attraction. There is not much clear-cut information available on what one could do and/or expect to experience there. Luckily for us, one of the guards on duty jumped in to explain things to us. He made us all stand together in one place and then walked away along the circumference to get to a point approximately diametrically opposite to us. By that time of the day, a horde of tourists were already inside the mausoleum trying to produce varieties of sounds and attempting to follow the ensuing echoes. A listener in the whispering gallery is somehow exposed to higher acoustic energy than one standing at ground level. We could hear a lot more noise while in the whispering gallery than when we stood next to the dummy tombs. In the midst of the prevalent cacophony, we recognised a faint and somewhat familiar voice say “can you hear me”? My friends and I looked at one another in shock. We realised that it was the guard speaking to us from the opposite side. Breaking through the short moment of disbelief, we all responded positively. Then he went ahead to recite a small portion of a song and we earnestly applauded spontaneously. Then, he said “let’s try this.” The dearth of available light and the gaping distance provided just enough visibility to be able to notice what he was up to on the other end of the diameter. Fortunately for us, the intense ambiance from incessant yelling, clapping and whistles had toned down for a couple of seconds and the sound of rubbing palms from ~40m away hit us at clearly discernible levels. Not to be taken literally, but we were indeed blown away by that experience. Earlier, my friends and I had tried yelling to communicate with each other while standing ~10ft apart along the circumference and we couldn’t hear each other at all. On the contrary, a very low intensity sound could be heard very well with roughly 10 times the separation. That is the power of the amazing acoustic property of the structure.

I had a very strong feeling that the sounds travelling diametrically across were not only propagated un-attenuated but were somehow amplified as well. Repeated tests of the palm-rubbing experiment continued to sound as though I was hearing the sounds played through a loudspeaker. The palm-rubbing sounds from the opposite side seemed louder than that of my own palms rubbing. Later, the guard said that if one were to visit the site very early in the morning before the deluge of tourists, he could clearly hear the sound of a wristwatch ticking.

Since I returned from the visit, several serious questions on technicalities have continued to haunt me – ‘what’, ‘why’ and ‘how’. What specifically in the architecture produces this acoustic behaviour? Why do sounds from only certain angles and distances get heard while others get heavily attenuated? If my suspicion were to be true, how does the architecture naturally amplify certain sounds? Detailed technical analysis would be much appreciated, but does not seem to be available anywhere yet. If one were to measure and study the perceived sound levels at both the producer and the receiver for different angle-distance combinations, we may be able to paint a picture answering some of the questions. Hope this article inspires someone to study, analyse and explain the science behind monument’s acoustic properties.

If you plan to visit the site, please play your role in reducing the ambient noise in consideration of others trying to appreciate the beauty of the whispering gallery. While at ground level, clap/whistle/shout once or twice only, do not overdo. And remember, the whispering gallery is called so for a reason, no shouting here.

Article Tags: 

Acoustics | Architecture | India
  • Bhavesh Patel

    I had been to Bijapur too and even I was astonished when I was able to hear the whisper of my fiend standing diagonally opposite. To add, guide mentioned that decades ago we could hear around 30 echoes. Hats of to the architectures !!

  • Lee

    Nice one Shyam.

    • http://www.shyamblast.com/ Shyam Madhusudhana

      Thanks Lee.