Author: Trevor Cox

I am a Professor of Acoustic Engineering at the University of Salford where I carry out research and teaching focussing on architectural acoustics, signal processing and audio perception. I am also an author and radio broadcaster having presented many documentaries on BBC radio and written books for academics and the general public.

Singing roads

A road which plays tunes using rumble strips.

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Want to listen to a poor quality, out-of-tune rendition of a famous melody when driving your car? No need for an expensive car stereo, a singing road can do this using wheel vibrations.

If you drift off the side of a road and hit a rumble strip, you’ll get a distinctive sound intended to alert you and prevent an accident. The pitch of the sound you get depends on the spacing between the bumps or ridges. So if you make lots of ridges like a rumble strip and vary the spacing between the ridges correctly, then different musical notes can be made. Close together ridges (say 6mm apart) give high notes, and far apart ridges (say 12mm apart) give low notes. Make the right pattern of ridges then as a car drives over them, a tune is played. Mind you, in most cases the sound quality is pretty poor, and if the car is at the wrong speed it sounds even worse. Rather amusingly, when Honda tried to create such a road for an advert, they got the spacing wrong and so their version of the William Tell Over­ture was very out of tune. Here is my acoustic analysis of the road.

Videos of musical roads in USA, South Korea, Japan and Denmark

Location

In City of Lancaster, USA, the road is found along the westbound stretch of Avenue G between 30th and 40th Streets West. It was moved from its original site following concerns about noise disturbing nearby houses.

Alternatively, the Japanese have the most melody roads: twelve listed here. Suggested optimum driving speed is 28mph (45km/h). Those shown on the map are:

  • Hokkaido: drive west
  • Route 370, Wakayama prefecture, plays Miagetegoran Yorunohoshiwo
  • Numata-shi, Gunma prefecture, plays “Natsuno Omoide (Summer Memories)”

The road in Anyang, Gyeonggi, South Korea is meant to play Mary Had a Little Lamb when driving at 100 Km/h and was designed to help motorists stay alert. However, the videos I have heard all sound pretty terrible and the tune is unrecognizable.

Credits and sources

  1. Map photo: shidax (c) some rights reserved

Singing Ringing Tree

High on the Pennine Moorsthis sculpture uses wind to generate discordant and haunting sounds.

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This piece of public art is high above Burnley on the Pennine moors. It uses the prevailing westerly winds to generate discordant and haunting sounds to accompany the view from Crown Point. It was designed by architects Mike Tonkin and Anna Liu in 2006 and won a Royal Institute of British Architects award. Not all the pipes create sound – some are just there to create the dramatic shape. The pipes that ‘sing’ create an unearthly choral sound, which is only audible at relatively close range on a windy day.

Location

Local tourist information

Credits

Norias of Hama

The groaning and creaking from these ancient water wheels is remarkable and unexpected.

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Damaged by the on-going war in Syria, I decided to leave this page here as a record of this sound.

The sounds these water wheels make aren’t very pleasant, but maybe sound tourists shouldn’t restrict themselves to pleasant listening experiences.

These gigantic ancient water wheels were used to raise water from the river and drop it into canals to irrigate fields. Although I’ve heard many water wheels, these ancient noria have a really unique and distinctive sound: creaking and splashing as the wood is distorted by the weight of the water and the endless rotation. Given that these are some of the oldest water wheels in the world, maybe they can be forgiven for their groaning and moaning.

Location

On the Orontes River in Syria

Credits and sources

Sea organ

The organ buried in the promenade makes a haunting but harmonious sound through the motion of the sea.

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Driven by waves this organ creates notes at random. Despite the unpredictability of the sounds, overall what is heard is surprisingly harmonious. This happens because the different organ pipes have been carefully tuned to only produce certain musical notes that sound good together [1].

The sculpture is seventy meters long and has thirty-five organ pipes built under the concrete; as you move along the promenade the sounds and harmonies change. The movement of the waves push air in and out of the organ pipes to create the notes. It was designed by architect Nikola Bašić.

Location

Visit Zadar website.

There is a wave organ in San Francisco and also a high tide organ in Blackpool. But the Zadar organ is the most tuneful and effective.

Credits

Ear of Dionysius, Sicily

Legend has it that the funnel shape of this cavern allowed the whispers of prisioners be overheard.

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This large limestone cave has a great sound legend attached to it. The story goes that the tyrant Dionysius (ca. 432–367 BC) used this place as a prison. The wedge shape of the cavern caused peoples’ conversations to be focussed and amplified at the roof of the cave, 22m above the floor. Supposedly this enabled guards to spy on prisoners by listening to the amplified sound through a small hidden opening at the top of the cave: even when the prisoners spoke in whispers.

“The tearing of a piece of paper makes a noise not unlike that occasioned by knocking a heavy stick against a stone” Conrad Malte-Brun, 1829.

Unfortunately, it’s no longer possible to hear the effect because of safety fears; in the past travellers were hosted up by rope and pulley to the opening. Consequently, a modern listener is just left to enjoy the reverberance at ground level, marvel at the legend and take in the cavern’s ear-like shape.

Gino Iannace and collaborators [1] have made measurements and test whether the spying myth is true. Rather disappointing, they found that any whispered conversations were unintelligible and lost in a blur of reverberation. The sound sample at the top of the page was reconstructed from their measurements. Even with carefully enunciated speech, it is hard to understand what is being said.

This video has good sound, but for some reason has been shot on its side.

Logistics

The Parco Archeologico della Neapolis, which includes the cavern, also has a Greek amphitheatre which sound tourists can admire.

Credits

  • Site suggested by Nick Antonio
  • [1] G. Iannace, L. Marletta, F. Sicurella and E. Ianniello, “Acoustic measurements in the Ear of Dionysius at Syracuse (Italy)” Internoise 2010.
  • Photo: Michael Wilson (c) some rights reserved

Tikal pyramids

Echoes off this pyramid create an unexpected chirping sound. But did the ancient Mayan’s deliberately design this sound effect?

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Tikal was the largest city of the ancient Mayan civilization and is probably Guatemala’s most famous tourist destination. If you stand at the bottom of the pyramid’s steps and clap your hands you get this incredible chirping sound. Echoes off buildings are common, but not ones that distort sound like this. Whether the pyramid was constructed to deliberately make this chirp is still a matter of debate. Reflections from the treads of the staircase are responsible for the echo. It’s down to geometry, later reflections are spaced further apart – all staircases have potential to chirp.

Location

Website. BTW The wildlife calls in this overgrown, runied city are also stunning: parrots, toucans and even howler monkeys.

Sources and credits

  1. Photo: Raymond Ostertag (c) some rights reserved
  2. Sound (c) sagejock

Booming Sand Dunes

Singing sand dunes can create loud drones during avalanches.

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(Your tablet ot computer loudspeakers may fail to reproduce this low frequency sound).

Some sand dunes make a strange low frequency humming sound a bit like the drone of a distant propeller aircraft. The sound can be surprisingly loud: in some cases it can be heard many kilometres away. This is something that has been known about for centuries: Marco Polo, the Emporer Baber and Charles Darwin all wrote about it [1]. For instance, Marco Polo wrote about his encounter in the Gobi Desert “[the singing sands] at times fill the air with the sounds of all kinds of musical instruments, and also of drums and the clash of arms.”

The sound is rather unusual and eerie – reminiscent of a bass musical instrument. The drone is caused by a synchronised avalanche of the sand grains. The pitch of the note produced depends on the size of the grains – and so each singing sand dune has its own distinctive voice pitch. But the exact reason for the grain synchronisation is still being argued about among scientists.

Logistics

Consider safety as you’ll be visiting a desert in the height of summer. About thirty dunes around the World boom. The large dunes most reliably sing in the summer when the grains are dry. Small dunes tend not to sing. As the videos show, you can start the avalanche yourself: once the sound has started it can continue for sometime after you stop pushing the sand. Do this on the leeward face of the dune (the side sheltered from the wind). The dune needs to be steeper than about 30 degrees.

Below is a list of locations gleaned from the Internet – it would be wise to check with locals about the exact locations.

  • Atlantic Sahara desert around Laayoune, Ghord Lahmar dune near Foum Agoutir, Morocco [2]. (Also Erg Ezzahar or screaming dunes)
  • Kelso Dunes near California’s Mojave Desert, off the Kelbaker Rd, north of Highway 40 between Barstow and Needles, Ca, USA [3]
  • Kelso, Sand Mountain (20-21 miles east of Fallon, Nevada on Highway 50, USA [3]
  • Crescent Dunes (about 15 miles west of Tonopah, Nevada, USA [3]
  • Dumont Dunes (60 miles north of Kelso, Ca, USA [3]
  • Big Dune (Amaragosa Valley, south of Beatty, Nevada, USA [3]
  • Eureka Dunes (Hanging Rock Rd, out of Bishop, Ca, USA [3]
  • 40 km southwest of Doha, Qatar
  • La Mar de Dunas and El Cerro Bramador, Copiapo, Chile
  • The Dune of Altynemel (“The Singing Dune”) in the valley of Ili River near Kapchagay, Kazakhstan
  • Near Liwa, South of the United Arab Emirates. In area known as the Empty Quarter
  • Dunes of Badain Jarin, Inner Mongolia, China
  • Dune Ming Sha Shan, The Mount of Singing Sand, DunHuang, Gansu, China

Credits

  1. http://www.its.caltech.edu/~nmvriend/research/
  2. http://www.pmmh.espci.fr/fr/morphodynamique/SongOfDunes.html
  3. Wild soundscapes: discovering the voice of the natural world, Bernard L. Krause, Wilderness Press
  4. Sound (c) Nathalie Vriend

Golkonda, India

Guides will demonstrate the clapping telephone, which was used to signal over long distances in this ancient city.

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This is the ruined city of the Kingdom of Golkonda (c. 1364–1512) which has several curious acoustic features including what has been described as an “amazing clapping telephone”. Clap near the entrance, and sound is reflected by a nearby building so that it can be heard a kilometer away at the highest point of the city, at the Bala Hisar pavilion. Some other quirk of this “magical acoustic system” means that close to the person clapping, the sound can only be heard within a few metres.

Demonstrating the clapping telephone. Lynn Robert Carter commented that the sound is more remarkable than appears on this video.
There’s also an interesting flutter echo as well

Logistics

11 km west of the city of Hyderabad, Andhra Pradesh state, south-central India. Suggested website for more information.

Credits

  1. Photo: mikecogh (c) some rights reserved

Gol Gumbaz Mausoleum

There’s crazy acoustics in this mausoleum: a whispering gallery and also an echo chamber..

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This vast 17th century mausoleum includes the second largest dome of its type in the World, but the acoustics are even more impressive. Getting to the whispering gallery underneath the dome involves climbing a hundred or so steep, crumbly steps. If you go early enough in the day when it’s not too busy, then you can test the whispering gallery. Sound hugs the inside of the dome so a whisper can be heard nearly 40m away on the other side of the gallery.

However, if you get to this place after the crowds have arrived then the soundscape isn’t so serene. Indeed downstairs, it’s more like a municipal swimming pool during a kids’ float session. They’ll be endless whooping and shouting as visitors test out the echo. The repeating echo in this building is unusual and well worth seeking out by sound tourists. Sound keeps bouncing around the dome, so that every 3 or 4 times seconds the sound whizzes past your ear. At quiet times, this repeating echo can be heard 7-10 times before it becomes inaudible.

Location

In Vijayapura, you need to arrive early if you don’t want to be deafened by a cacophony of mass acoustic-induced hysteria.

Credits

  1. Photo: Ashwatham
  2. Sound © Audio Ease. Thanks to Arjen from Audio Ease.

Pisa Baptistry

The rich reverberant sound in the Baptistry of Pisa lasts an astonishingly long time, to the delight of all tourists, not just sound-ones.

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Under the dome of the Baptistry in Pisa a stunning acoustic effect can be heard. Notes sung here last so long, it’s actually possible to accompany yourself: new notes will harmonize with old ones still reverberating around. The Baptistry Guards will often demonstrate this beautiful effect.

The key to the remarkable acoustic is that there’s very little soft material about to absorb the sound. Consequently, notes rattles around the space for a long time, some suggest for over 12 seconds, before the sound dies away and becomes inaudible.

Logistics

To enjoy the wonderful acoustic arrive early before it gets too busy. Website with opening hours.

Credits

  1. Sound (c) jnbcarvalho
  2. Photo: gaspa (c) some rights reserved