My Science School

            Forests are often cherished for the peaceful, natural sounds they offer. Imagine how beautiful it would be if these sounds are heard louder! That is exactly what a few students did in a deep forest of Estonia. The giant timber megaphones that they built amplify the natural sounds of the Estonian Voru forest.

            Created by the students of interior architecture at the Estonian Academy of Arts, the three wooden structures or ‘ruup’, as they are called in the local language, are installed in the Pahni Nature Centre near the Latvian border.

            The main purpose of these installations is to act as amplifiers of the natural sound of the forest, like the chirping of birds, resulting of leaves etc. but the megaphones are so huge that they also serve as lounging spots for travellers inside the forest. Each structure, conical in shape, has a diameter of three metres.

 

            Sound mirrors or acoustic mirrors are huge concrete structures that were designed as an early warning system for Britain. The purpose behind this magnificent creation was to detect enemy aircraft. Three designs of 6 metres, 9 metres, and 60 metres were made and all of them can be seen in Great stone, located in the north east side of the Dungeness Nature Reserve. They were developed by Dr. William Sansome Tucker.

            Also called the ‘listening ears’, the mirrors were helpful during wars. Built during the late 1920s, the sound mirrors were part of the British national defence strategy. They did work well, and detected slow moving enemy aircraft before they came into sight. In fact, they were able to give a fifteen-minute warning of an approaching aircraft.

            However, sound mirrors were outdated with faster flights coming into use. Later, radars were developed. Today, they remain as preserved monuments with many visitors throughout the year.

            The Ekko is a man-made work that exploits the possibilities of sound to produce a magnificent experience. At first glance, it is a circle of concrete pathway with wooden frames of incrementally different dimensions surrounding it.

            We could call it a snaking tunnel made of wood. As you walk on the pathway that is inside the work, you experience a unique sound. This is caused by the footsteps and voices in the corridor which are collected by the microphones hidden within the wooden beams. These sounds are remixed by a computer and played back as distorted echoes through tiny speakers.

            The brilliant work is installed in hjallerup, Denmark. Created by Thilo Frank, Ekko offers a special walking tour and sound experience. There were around 200 wooden frames used for the work. Each of them is angled slightly, so the construction turns in on itself along a 60-metre corridor.

            The Prenzlauer Berg tower is the oldest water tower in Berlin, built in 1877. It is a tall, round building in which water was stored in a tank on top. It supplied water to the city until 1952 and since then, has become a major landmark.

            During the World War II, the machining building adjacent to the tower was used as a concentration camp site. But what is equally interesting about the tower, are its acoustics.

            In fact, dark and concealed places as water tanks and tunnels can heighten the intensity of sound experience. Taking advantage of this, two artists had placed their installations in the water reservoir of Prenzlauer Berg.

            One is the site-specific installation ‘Eternal Darkness’ created by German composer Robert Henke. The reservoir’s round corridors provided the backdrop for this sound installation. Another work was an installation by Canadian artist Gordon Monahan. It featured resonating metal records that hung beneath the vaulted ceiling.

            The Brunel Museum is a museum in the Brunel Engine House of London, designed by Sir Marc Isambard Brunel. It was developed as part of the infrastructure of the Thames Tunnel, which runs from Wapping to Rotherhithe at a depth of 22.8 metres below the surface of the River Thames.

            For years, the tunnel was used as a shopping arcade and entertainment centre. The entire length of 396 metres was illuminated with lights, and people would walk down for shopping. By 1869, it was converted into a railway tunnel for the East London underground line up, until 2007.

            In 2016, the museum opened the Engine House as an exhibition space with a café and a rooftop garden. The inaugural ceremony witnessed performances by many musicians. One of them said that the acoustics was challenging and there was an amusing ‘whispering gallery effect’.

            Gol Gumbaz is a popular heritage structure in the Bijapur district of Karnataka. It was built by the Adil Shahi dynasty as the tomb of the Adil Shahi ruler Mohammad Adil Shah under the expertise of architect Yaqut of Dabul.

            The literal meaning of Gol Gumbaz is ‘circular dome’. With the dome, minarets and other features, the structure is a visual delight and stands as a perfect example for the Deccan style of architecture.

            What makes the dome unique is its Whispering Gallery. It is a circular gallery below the tomb where even the slightest whisper gets amplified and travels a distance of more than 40 metres! That means, even sounds produced in low strengths from one end of the gallery can be heard at the other end, very clearly. Besides, there is an incredible echo effect within the place. It enables a clap to be echoed for more than 10 times!

            The Sydney Opera House is a famous performing arts centre in Australia, functioning since 1973. Designed by Danish architect Jorn Utzon, the building comprises multiple performance venues, and hosts more than 1500 performances annually. The Concert Hall, Joan Sutherland Theatre, Utzon Room, the Drama theatre and the Playhouse are a few of the venues.

            However, in spite of its repute, the Opera House has been severely criticized for its bad sound system. One of the major complaints is that the acoustics absorb sound and drain performances of their energy. This is particularly true in the case of the Concert Hall which has a 25-metre ceiling that causes sound to get lost. At the same time, the proportion of a few other rooms and their ceilings are so problematic that they create unwanted reverberation.

 

            The contributions made by the Ancient Greeks to the world of acoustics are unparalleled.

            One of them is the amphitheatre of Epidaurus, designed by Polykleitos the Younger, around the 4th century BC. The theatre had a tripartite structure, that is, an orchestra, auditorium, and stage building. There were also 34 rows of limestone seats that could accommodate 14,000 people.

            The acoustics of the place was such that a performer standing on the open-air stage could be heard in the back rows, almost 60 metres away.

            Experts attribute this rare feature to the arrangement of seats. According to them, the stepped row of seat structure was perfectly shaped so as to act as an acoustic filter. The seats suppressed low-frequency sounds that formed the major component background noise like the murmur of a crowd. This in turn, reflected high-frequency noises of the performers off the seats, and back toward the seated audience.

            We have read that most humans can hear sounds between 20 and 20,000 hertz. Ultrasounds are those above this limit or specifically, above 20,000 hertz. They are not different from the normal sound in terms of physical properties. But the only difference is that they can be heard and produced by only a few animals like bats, moths, dolphins etc. and not by humans. In other words, the range of ultrasound begins where our sonic range ends.

            The uses of ultrasound can be seen in electronic, navigational, industrial, medicinal and security applications. Let’s look at a few examples in brief.

            In some cases, ultrasound is used to detect objects or to measure distances. They are also helpful in testing products and structures.

            In addition to these, ultrasound is used in the field of medicine to view the internal organs of our body.