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.
A spherical room that allows you to whisper sweet nothings in your ear!
The Mapparium is a giant hollow globe of the world, with the seas and continents vividly drawn on stained glass. It was built in 1935 following a suggestion by architect Chester Lindsay Churchill. It took eight months to paint and bake all 608 glass panels, which are mounted on a spherical bronze frame.
You traverse a walkway cutting through the center of the Earth linking up two opposite points on the equator. Three hundred lightbulbs illuminate the globe from the outside. Looking at the world from the inside out is an odd experience, but what also strikes visitors are the strange acoustics, which were an accidental by-product of the geometry.
One of the effects you’ll hear is false localisation:
“Suppose you are on the Mapparium bridge facing South America. There is a source of noise to your right, but you discover that you hear the noise coming from your left!”
William Hartmann, Michigan State University
This happens because the reflections from the globe are focussed and very loud. Your brain thinks the sound is coming from the reflection direction and not direct from the source. This focussing also allows you to do things like whisper in your own ear!
As you approach the exact center of the Mapparium sphere you suddenly become aware of strong reflections of your own voice . . . If you sway to the left, you hear yourself in your right ear. If you sway to the right, you hear yourself in your left ear.
Looking like a cluster of igloos, this sound sculpture is ideal for traditional Icelandic singing.
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“It is great fun visiting this work of art, trying to sing in all the domes teaches one a lot about acoustics. This area is quiet and tranquil and one doesn’t have to feel embarrassed about raising one’s voice to sing out loud”
Constructed from smooth thick concrete, each of these reverberant chambers has been tuned to a different frequency corresponding to a tone in traditional Icelandic five-part harmony. It’s by German artist Lukas Kühne and is called Tvísöngur or The Duet. You can hear the resonances either by singing, or through the wind whistling through the openings.
Here is a short snippet of singing without (anechoic) and then with the sculpture.
Richard Serra’s giant concave artworks can produce an astonishing diversity of sounds.
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I stumbled across this Richard Serra sculpture when flying back from Tononto Airport. Clapping is one way of exploring the space, it’s like having a giant sound-effects unit to play with. Get the right place, and the focused reflections from the arcs follow repetative patterns creating Gatling gun echoes.
It’s also fun to listen out for people with noisy roller suitcases walking down the middle. What’s nice about this sculpture is being outside a gallery means the public can play with the sound. Here is a spot of impromptu singing exploiting the acoustic.
Pearson Airport. Terminal 1, after security, International departures, hammerhead F.
This large sculpture plays with the sound of the wind and waves.
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If you stand in the center of the structure, the sound of the wind and the waves at the bottom of the cliff are intensified. The experience makes you feel as though the elements are swirling around your head.
Expedia travel guide
Created by Basque artist Eduardo Chillida, this curved concrete sculpture creates a clear and strong amplification of the sounds of the sea crashing at the bottom of the cliff. You have to stand in the center of the sculpture. Close your eyes, you will hear the noise of the waves breaking against the rocks, but the sound comes from the upper area of the sculpture. Apparently it is an accidental sound scuplture, with the artist being surprised when he first heard it.
Thanks to J.Oscar for providing some first hand experience of what is going on (see first comment). It’s a reflection from the underneath of the upper ring. But the other key acoustic element is the lack of any sound straight from the breaking waves to your ear because the edge of the cliff is in the way. This lack of direct sound is what causes the image to falsely appear to come from above, and also why you’re surprised to suddenly hear the sea as you walk into the focus point.
Does anyone have recordings?
The scultpute can be found in the grassy Parque del Cerro de Santa Catalina, at the top of Cimavilla, Gijón.
An accidental sound sculpture created by a wierd flutter echo.
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This doesn’t appear in travel guides to Oslo, but every sound tourist should look it out if they’re in town. Here is me describing the strange acoustic, and as I walk into the middle of the ticket hall you can hear how my voice takes on a strange warbling. (The end of the audio when I walk out from the centre is the most dramatic).
Flutter echos are caused by repeated reflections arriving at regular intervals. In the graph below, you can see them as a set of clearly spaced spikes in the response to the room to a balloon burst. A warble is heard when the reflection pattern has some subtle irregularity about it. There also has to be a delay of more than about twenty-milliseconds for the brain to sense a temporal fluttering.
The architect Arne Eggen kindly sent me an article about the station that includes a plan for the ticket hall. The red lines are added by me to show that the inside space isn’t a simple cylinder but two half cylinders of different radii joined together. This means focussed reflections from the top half-cylinder arrive quicker than those from the bottom half-cylinder. But it is actually more complicated than that, because the domed roof also plays a role in breaking up the regular reflections.
The other thing I learnt from the architect was it wasn’t deliberate. And the railway company didn’t like the effect when it was first built. However, once musicians and others started visiting the remarkable acoustic as a tourist attraction, the train company grew to love it and put a plaque on the floor that says ‘Akustik Skulptur.’
This railway tunnel creates an extraordinary metallic flutter.
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This old railway tunnel near Sheffield creates an extraordinary metallic flutter when you shout or clap your hands. I was alerted to this strange acoustic when I was interviewed for the Channel 5 programme Walking Britain’s Lost Railways. While many tunnels have lots of reverb, it’s unusual to have such a warbling effect.
The warble is a type of flutter echo, caused by repetitive reflection paths. The animation shows sound being modelled as a simple bouncing ball. At each wall the ball follows the law of reflection (angle of incidence = angle of reflection). The source is the black circle and the red circle is where the listener is. You can see that the sound keeps returning to the receiver, but it takes a few reflections before it returns. There is a pattern of regular reflection arrivals, but the bowed shape of the tunnel creates paths that traverse the width more than once before returning to the receiver. There’s a slightly longer explanation on my acoustical engineering blog.
If you want to experience it yourself, it’s open as part of the National Cycle Network. The tunnel is here.
A beautiful reverb surrounded by vivid and explicit frescos.
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This doesn’t appear very high on lists of tourist attractions in Oslo, but it deserves to be much better known. It was built in 1926 by the artist Emanuel Vigeland as a gallery. Luckily, for sound tourists the windows were later filled in when it was turned into the artist’s mausoleum. Every surface in the room is now concrete or stone, and this means the sound bounces and rings around the room for an extraordinary long time. Norwegian acoustician and composer Tor Halmrast describes it as the most reverberant place for its size that he had ever experienced. When I sang a few notes, the notes hung in the air for 10-15 seconds. I can see why musicians like to perform there, because the reverb is very rich and seems to gradually cascade down from the ceiling.
Here is a simple balloon burst I recorded:
An acoustic analysis of the balloon burst and the acoustics can be found here.
The room is more dimly lit than the photo above shows, but after a while once your eyes have adapted to the dark you start to pick out the frescos covering the walls and ceiling that depict conception, life and death in very explicitly. One of the most famous mural is above the door just above the urn holding the artist’s ashes. A plume of babies rise above a pair of skeletons reclining in the missionary position.
A claustraphobic silence that some find unpleasant and others love.
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When someone talks in a full anechoic chamber, their voice sounds muffled, like your ears need to pop while in an aircraft. Some visitors find the disjoint between the visual and aural unsettling. This is a room where you can see but not hear walls. One scientific study showed that if you turn the lights out, after a while some visitors will start to have hallucinations in the chamber.
Anechoic chambers are incredibly quiet and the walls of the room don’t reflect sound. This enables acousticians to test products and sound phenomena without interference from outside noises or reflections from the walls. A well designed anechoic chamber is so quiet that no sound enters your ear canals, the only sounds you hear are generated by your own body. You might hear blood moving through your head and/or a high pitched hissing originating in the auditory nerve. But the extraordinary quiet isn’t the main reason why some visitors ask to leave the chamber. The walls, floor and ceiling are covered in absorbent wedges that mean no sound reflects back to you when you talk and this sounds impressive.
This video is the best illustration I know for how quiet the space is:
There are many anechoic chambers in the world, but you need to find a high quality one with an absorbing floor and very low background noise level to get the full aural experience. At Salford University, our anechoic chamber opens up during open days for public tours.
A disused listening station from the Cold War that has powerful echoes from the near-spherical radome and you can whisper into your own ears.
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The abandoned spy station at Teufelsberg, Berlin is on top of Devil’s Mountain rising up from the Grünewald forest. This man-made hill was constructed from millions of cubic metres of rubble created by bombing raids and artillery bombardments during World War II. The remarkable acoustics is in the almost spherical radome on top of the highest derelict tower. These domes used to cover listening equipment used by the British and Americans to spy on the East. There are a number of different sounds effects you can play with in the dome. Climb on top of the concrete plinth and get into the middle of the sphere and the strong focus creates richocheting sounds when you clap your hands.
Alternatively, you can try whispering just off-centre, and see if you can find the right spot for whispering into one of your own ears. If you go to the side of the dome and a friend goes to the opposite side, you can use the walls as a whispering gallery. Whisper into the wall and your voice will skim the inside of the walls and your friend will hear your words apparently emerging from the graffitied walls. If instead of whispering quietly you make a loud bang near a wall, then you can hear the bang pass you several times as it does complete circuits of the dome walls. This sound example has three balloon bursts:
Being reverberant, the dome also attracts musicians to play music.
Mimics the sounds of the rainforest, from Kookaburra to chain saw.
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The male superb lyrebird attracts females by probably the most extravagant animal call in the world. The male mimics all the sounds from the forest, includeing the calls of other birds. Ones brought up around manmade sounds impersonate the roar of a chainsaw, the screech of a car alarm and the click of camera shutters. Lyrebirds display this vocal virtuosity not just during the breeding season, implying the calls are not just about finding a mate but also used to defend territory. During the breeding season they use a display mound to sing from for hours, with the calls travelling up to a kilometre through the forest. The BBC video of the Lyrebird is very funny and was voted by viewers as their favourite Attenborough moment.
The map shows the location of Healesville Sanctuary but the Lyrebird can be seen elsewhere in south-eastern Australia.