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Tag archives: acoustics

Can a concert hall have a perfect acoustic?

Photo of Lesley Garrett

Sound engineer Paul Waton and soprano Lesley Garrett discussing theatre acoustics at the Royal Opera House. (Courtesy: Brian Slater)

 

By James Dacey

Concert hall acoustics was the theme of a fascinating panel debate last night at the Royal Opera House (ROH) in London. Among the speakers was British soprano and presenter Lesley Garrett who shared her views on the acoustics of some of the great concert halls in which she has performed. She was joined by acoustics engineer Trevor Cox, acoustics consultant Helen Butcher and sound engineer Paul Waton, who has recorded a range of classical concerts for the BBC. Insight: the Art and Science of Acoustics was co-hosted by the Institute of Physics, which publishes Physics World.

Cox – who featured in our 2014 podcast about sonic wonders – set the scene by describing some of the fundamental acoustic considerations in designing a concert hall. We heard clips of Cox playing a saxophone in an “anechoic” chamber, followed by the same sax lick performed in an oil tanker – the place with officially the longest echo in the world. Cox’s point was to show the difference between high clarity at the one extreme and intense reverberation at the other. The sound wasn’t quite “right” in both cases. “Concert hall design is about finding a pleasing balance between these two extremes,” he said.

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Sounding off about valleytronics

Photograph of a valley in Glacier National Park in the US

Valley state: real-life landscapes can be as beautiful as their condensed-matter counterparts. (CC BY-SA BorisFromStockdale)

By Hamish Johnston

Condensed matter is a physicist’s paradise because of the seemingly endless number of ways that atoms can be rearranged to create systems with new and exciting behaviours. A great example of this is the emerging field of “valleytronics”, which is concerned with a property of electrons that emerges in some semiconductors and 2D materials such as graphene.

The eponymous valley is a local minimum in the conduction band of a solid that “traps” electrons into a specific momentum state. Things get interesting when a material has two valleys that result in two distinct momentum states. In some materials these states resemble the quantum-mechanical property of spin: an electron can be in one of two spin states (up or down) and it can also be in one of two momentum states. As a result, this property is sometimes referred to as valley pseudospin.

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How the banjo got its twang, love in the time of science, award-winning astro images and more

Five string banjo showing the position of the bridge on the head. (Courtesy: Wikipedia/CC BY-SA 3.0)

Five string banjo showing the position of the bridge on the round head. (CC BY-SA 3.0 / DMacks)

By Tushna Commissariat and Hamish Johnston

Folk and country music often blends the sharp twang of a banjo with the mellow and sustained tone of a guitar.  While the two instruments appear to be very similar – at least at first glance – they have very different sounds. This has long puzzled some physicists, including Nobel laureate David Politzer, who may have just solved this acoustical mystery.

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Stretching and spinning droplets using sound

Mirror made from tiny polystyrene spheres (Courtesy: Grzegorczyk et al Phys Rev Lett 112) 023902

Mirror made from tiny polystyrene spheres. (Courtesy: Grzegorczyk et al., Phys. Rev. Lett. 112 023902)

By Hamish Johnston

There are two fantastic papers in Physical Review Letters this week that made me smile. Both of them are about controlling macroscopic objects using waves. While there are practical applications for both techniques, I can’t help thinking that the authors did the work for the sheer joy of it.

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Why do beer bottles foam when struck on top?

A foamy mess in the making (Courtesy: Javier Rodríguez-Rodríguez)

A foamy mess in the making. (Courtesy: Javier Rodríguez-Rodríguez)

By Hamish Johnston

We’ve all had a friend who does it – you’re deep in conversation at a party, beer bottle in hand, when someone sneaks up and taps the top of your bottle with theirs, causing a foamy mess to erupt from your bottle. And to add insult to injury, their bottle doesn’t foam.

Now, physicists in Spain and France have studied this curious effect and gained a better understanding of how it occurs. While their work won’t prevent wet shoes and slippery floors at university social gatherings, the researchers believe their work could provide insights into geological features such as oil reservoirs, mud volcanoes and “exploding lakes”.

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Meet the engineers who talk to aeroplanes

Fancy a chat with this Boeing 787 Dreamliner? (Courtesy: Boeing)

Fancy a chat with this Boeing 787 Dreamliner? (Courtesy: Boeing)

By Ian Randall

For most people, it’s considered rather eccentric to talk to inanimate objects – and if the objects seem to be talking back, then it’s probably time to seek medical advice! Not, however, for Alex Ng and his colleagues at the University of Adelaide in Australia, who are working on a way to “chat” to buildings, bridges, aeroplanes and other structures, so they can report back on their structural health.

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Surround no sound?

By Tushna Commissariat

Image of the 3D acoustic cloak

A picture of the 3D acoustic cloak (left) and the cloak being tested in an anechoic chamber (right). (Courtesy: Physical Review Letters)

Invisibility cloaks seem to fascinate scientists and the public in equal measure, and every few months a novel design for some sort of metamaterial that cloaks either light or sound catches our eye, if you excuse the pun.

This week, we came across a group of researchers in Spain that claims to have designed, fabricated and tested the first “directional 3D acoustic cloak” that works for airborne sound. Previous designs of acoustic cloak work in water and air, but only if the sound propagates in 2D. Also, many cloaks only work within a narrow band of frequencies, limiting their uses.

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