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.

Bearded Seals

The extraordinary long drawn out glissandos make this a strange animal calls.

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Photo by kerryinlondon CC BY-ND 2.0

The bearded seal (Erignathus barbatus) is named after the whiskers on its face, but that’s not the most remarkable thing about this animal. The seal produces incredibly complex vocalisations, with the long drawn out glissandos that trill and spiral down in frequency. As the seal creates this call, they spiral downwards releasing bubbles, before surfacing in the centre of the circle.[1] Vocal athleticism in animals is thought to arise because females judge the fitness of a singing male by the quality of the song. Evolutionary pressure therefore drives the males to sing with ever more outlandish effects. For the bearded seal this means producing spiralling glissandos of extraordinary length. The recording above is from Point Barrow, Alaska using an underwater microphone (hydrophone).

Location

The sounds are only heard in the breeding season that lasts from about late March through mid July.[1] The bearded seal can be found in the Arctic waters of both the Atlantic and Pacific Oceans.

Credits and sources

Echo Bridge

Bridge arches can have great echoes, this one is meant to repeat a human voice up to 15 times

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Built in the 1870s, this large arched bridge spans the Charles River. There are steps down to a specially built listening platform so you can hear the sound effect. In September 1948, Arthur Taber Jones wrote to the Journal of the Acoustical Society of America, detailing a small study. ‘A handlcapp [sic] is returned in a series of about a dozen echoes of decreasing loudness, and at a rate of about four echoes per second.’ [1]

By Daderot – Own work, CC0

The question Jones posed in his article was whether the sound was skimming around the inside of the curved arch, like a whispering gallery or propagating horizontally just above the water. The video below, created with a modern acoustic prediction model shows how sound moves under the bridge. No wonder Jones struggled to work out what was going on, because it seems that the sound both skims around the arch and bounces back and forth horizontally just above the water.

While Echo Bridge is unique in having been a subject of scientific study, I’ve found that other arched railway and canal bridges have the same sound effect once you know the general shape to look out for.

Location

A Walking Tour of Hemlock Gorge (including a visit to the echo platform). The bridge spans the Charles River between Needham and Newton.

Sources

Thanks to Jonathan Sheaffer for modelling the sound propagation.
[1] A. T. Jones, “The echoes at Echo Bridge,” J. Acoust. Soc. Am. 20, 706-707 (1948).

Hamilton Mausoleum

This mausoleum once held the World record for the room with the ‘longest echo’

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During the World record attempt, it took 15s for the booming reverberation caused by slamming one of the grand doors shut, to die to silence. When I visited the first floor chapel it was certainly very reverberant. It’s like being in a large church or cathedral, impressive but there are more reverberant spaces in the World. The reverberation time at frequencies imporant for speech has been measured at about 9 seconds. A guided tour around the chapel is worth taking because you can then enjoy some of the tales about the colourful Duke and his descendents. The very reverberant space attracts musicians from around the world to perform and record.

Cupola and test loudspeaker
Looking up at cupola with test loudspeaker in foreground

A less well known acoustic phenomenon in the chapel is the whispering walls in the cylindrical alcoves. If you and a friend stand at opposite sides, you can whisper to each other by talking into the wall.

Location

Close to Glasgow, book a tour organised by Low Parks Museum and Hamilton Mausoleum.

Echo, Château de Chinon

A strange local rhyme exploits this distinctive echo.

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This way to the echo

How can a Sound Tourist resist a road sign pointing towards an echo? Despite having no decent sound recording equipment, no aptitude at speaking French and ignoring the fact I was wearing a cycle jersey of dubious taste, I attempted to capture the event on my mobile. You might need to turn up the volume to hear the echo.

A description of the echo appears in the Rough Guide to the Loire which describes a traditional local rhyme which exploits the timing of the echo:

Me: Les femmes de Chinon sont-elles fidѐles

Echo: Elles?

Me: Oui, Les femmes de Chinon

Echo: Non!

Which translates into English as:

Me: Are the women of Chinon faithful?

Echo: Them?

Me: Yes, the women of Chinon

Echo: No!

And I can confirm the description is correct –  by that I mean the echo rhyme really works, I know nothing about the faithfulness of Chinon women! The echo is a reflection from the side of the chateaux and is beautifully clear (if a little quiet for recording on a mobile).

Location

If you exit the Château visitors’ centre northwards away from the town (it seems like the back entrance) you’ll pass L’Echo de Rabelais. Across the road you’ll see a big sign to the echo vineyard close to the smaller sign for the echo. Follow the small Rue de l’Echo for 200m and you’ll find a small raised vantage point. A

Stonehenge Replica

Experience a impression of the ancient acoustics of Stonehenge.

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What was the acoustic like within Stonehenge thousands of years ago? It’s difficult to get an impression at the real Stonehenge because too many stones are missing or displaced. However, a trip to this complete replica in the USA gives an impression of the old site. The replica was built as a monument to those who died in World War 1. Although made from concrete rather than stone, the acoustic within the circle is similar to the original.

Rupert Till explores how a drum beat is changed by the stonecircle.

The effect of the stones can be heard by comparing these two recordings. The first is a recording of clapping away from the standing stones out in the open and the second a recording of clapping within the stone circle. The sound can be heard to ring and reverberate within the stone circle – it is surprising how long each clap rings for, considering there is no ceiling on the stone circle to stop the sound disappearing into the sky.

Clapping away from the standing stones out in the open
Clapping within the stone circle

Location

The Maryhill Stonehenge is part of the Maryhill Museum of Art three miles east of the museum just off Highway 14.

Credits

Sounds from Bruno Fazenda University of Salford and Rupert Till University of Huddersfield

Coloured Canyon

A place to hear nothing. Although you might be surprised to find out when you get there, that your body isn’t as quiet as you think.

We’re not used to hearing complete silence. Normally there’s sound around us: the distant drone of traffic noise, leaves rustling in the wind, the hum of insects, etc. To find complete silence in nature, you need to travel to places which have little vegetation (so there are no other animals about) and you need to find a spot which is sheltered from the wind, or travel on a windless day. A good spot to hear absolutely nothing is the depths of the Coloured Canyon in Sinai. And according to Adam Lawrence who suggested this place “Oh, it looks pretty good too.”

Location

Tours are available from hotels on the nearby red sea coast (Gulf of Aqaba side of Sinai). Getting there involves a long jeep ride and a hike. Leave early in the morning to avoid the heat and to get there before too many people ruin the quiet.

Credits

Photo by Tanya Dedyukhina, CC BY 3.0

Whistled language

Use to communicate over large distances.

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How do you communicate over large distances on a mountainous island full of deep ravines? On La Gomera in the Canaries, inhabitants developed a whistling language to save themselves long and arduous treks. Maybe we should all use it when the network coverage is poor.

The whistling mimics the sounds of the local language, using variations in the notes to represent words. Indeed, brain scans show that listeners are exploiting the same parts of the brain used in normal language processing when interpretting the whistling.

Although other places in the world have whistling languages, this one is unusual because it’s so sophisticated and practised by thousands of inhabitants. Indeed, the island habitants learn the language at school. It’s importance has been recognized by Unesco.

Waiter demonstrates language for tourists

Location

La Gomera in the Canaries

Credits

  1. Sound extracted from BBC interview
  2. vilb (c) some rights reserved
  3. Suggested by Bernard Berry

Way of Silence

This tiny beautiful island has a Way of Silence – a waymarked soundwalk.

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“‘If you can be yourself, you are everything,’ says one sign. ‘Listen to the water, the wind, your steps,’ urges another.” [1]

On the small Isola San Giulio (St Julius’s Island) in Italy, there’s a Sound Walk. The ‘Way of Silence’ is a flagged alleyway that goes around the island, with plaques that instruct you to listen out for particular sounds. Such a process of walking and structured listening was pioneered by acoustic ecologists as a way of better understanding soundscapes.

When you tire of the sound walk, turn around and follow the back of the plaques which have different messages, forming the ‘Way of Meditation’.

Location

Lonely planet page on the island

Credits

  1. http://www.orta.net/eng1/indipendent.html
  2. Photo by oliver hiltbrunner (c) some rights reserved
  3. Suggested by Gianluca Memoli

Great Stalacpipe Organ, USA

Ringing stalactites create strange ethereal sounds from this huge musical instrument.

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This is a bizarre musical instrument. It was dreamt up and painstakingly constructed by Leland Sprinkle, a mathematician and electronic engineer in the 1950s. Rocks that ring have been used as musical instruments for thousands of years. But this is the only lithophone I know of based on stalactites.

It’s claimed to be the largest natural musical instrument in the world, generating a beautiful, ghostly and disorientating sound. The cave acoustics make it difficult to locate where the sounds are coming from. 37 stalactites produce the different notes of a musical scale. But the tuning isn’t entirely natural, as some sanding of the natural formations was needed to get the notes exactly in tune. Small rubber hammers strike the stalactites; these are electronically controlled by an organ keyboard.

Locations and logistics

Luray Cavern’s website with opening hours etc.

Credits and sources

  1. Sound released by Luray Caverns into public domain
  2. Photo: KristopherM (c) some rights reserved
  3. Photo:lossanjose (c) some rights reserved

Bell Caves

What makes the echoing sound of these caves unusual, is the way the different chambers are connected together.

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The Bell Caves have a unique sound. What makes the Bell Caves unusual and worth a visit is the acoustic effect created by the connections between the chambers. As the sound moves between the large chambers along the passageways, a very distinctive reverberance is heard, as sound sloshes about from one chamber to another.

The caves were quarries which were excavated at different times in history, but it is claimed some date back to the 4th century B.C. The walls are made of beige coloured limestone.

Location

The Bell Caves are in the Beit Guvrin National Park. The park also contains a Roman amphitheatre.

Credits and sources