Metamaterials: Soundproofing The Future

Noisy neighbours, deafening air conditioning units, those disconcerting aeroplane creaks and whirs. These are all noisy nuisances that we think of as part and parcel of our day to day lives.

Until now.

It turns out some smart people in the worlds of science and engineering have been busy exploiting new discoveries made in metamaterials to develop new mediums that could effectively mute everyday objects and mechanisms.

Metamaterials are artificially created materials, often down to individual cell units. By exploiting the theories of negative indexing and negative refraction, these new materials can form the building blocks of new objects with novel acoustic properties. They effectively allow the manipulation and control of the behaviour of sound in objects by scattering, diverting and attenuating soundwaves.

Devices that cloak objects from sound, the control of soundwave vibrations in consumer appliances, domestic windows that let in air, but not sound; these are all future possibilities in a quieter world, thanks to metamaterials.

Acoustic-metamaterials-infographic

The creation of ‘metamaterials’ – materials with properties found nowhere in nature – means scientists and engineers are now able to manipulate the acoustic properties of everyday objects – making aeroplanes, washing machines and domestic walls immune to soundwaves.

Metamaterials are artificially created materials, often down to individual cell units. By exploiting the theories of negative indexing and negative refraction, these new materials can form the building blocks of new objects with novel acoustic properties. They effectively allow the manipulation and control of the behaviour of sound in objects by scattering, diverting and attenuating soundwaves.

Aeroplanes:

Diagram of metamaterial in plane structure

Depiction of how metamaterials could replace traditional honeycomb structures.

Aeroplanes use a honeycomb structure to support the floor and ceiling of their cabins. Unfortunately, for the flight-phobic of us, this structure is an effective transmitter of soundwaves – resulting in those off-putting mechanical noises you hear while in your seat.

Scientists from North Carolina have created a negative density insulator made from latex, which when wrapped around the honeycomb directs noise away from the structure – keeping those whirrs and creaks out of the cabin.

Consumer Appliances:

Realisation of adaptive structures. Credit: IDMF

Realisation of adaptive structures.

Swiss scientists have developed a metamaterial that combines phononic crystals with tiny electrically charged disks that make the material adaptive. The composition of the material is able to be changed on demand thanks to the adaptive crystal structure.

This would allow materials to be manipulated to remove physical connections and prevent vibrations in objects. In short – quieter washing machines.

Block Party Bass:

Soundproofing foam

New ultra-thin metamaterial panels could replace traditional soundproofing methods.

Hong Kong researches have developed a metamaterial no thicker than a ceramic tile, which can block noise across a wide frequency spectrum.

By combining latex and small plastic buttons tuned to resonate at different frequencies and then stacking these alternating membranes on top of each other – researchers have been able to create a broad-spectrum thin panel that could block out pesky noise from your neighbour’s man cave parties.

Soundproof Windows For a Good Night’s Sleep:

Korean scientists have developed a window that can separate air from sound, and then effectively block soundwaves.

By combining negative density materials and resonance chambers that counteract the movement of sound – researchers have created a window that allows the passage of air while effectively blocking sound. Fresh air for those hot nights, without bothersome traffic noise.

Acoustic Cloaking:

3D-printed acoustic cloak prototype

The prototype of the 3D-printed acoustic cloak. Credit: Duke University

Engineers from Duke University have developed a 3D acoustic cloak that can reroute soundwaves around an object, effectively making that object invisible to soundwaves.

Made from carefully constructed perforated plastic sheets, the cloak alters the trajectory of soundwaves so it is as if the object being cloaked was not there.

The system could provide defensive measure for military applications – such as masking underwater vessels from sonar detection.

References:

  • Zigoneanu, Lucian, Bogdan-Ioan Popa, and Steven A. Cummer. ‘Three-Dimensional Broadband Omnidirectional Acoustic Ground Cloak’. Nature Materials 13.4 (2014): 352-355. Web. 30 Oct. 2015.
  • Rathi, Akshat. ‘This New Man-Made Material Could Get Rid Of That Horrible Airplane Noise’. Quartz. N.p., 2015. Web. 30 Oct. 2015.
  • New Scientist,. ‘Latex Could Silence Noisy Neighbours’. N.p., 2015. Web. 30 Oct. 2015.
  • MIT Technology Review,. ‘Redesigned Window Stops Sound But Not Air, Say Materials Scientists | MIT Technology Review’. N.p., 2013. Web. 30 Oct. 2015.
By |2018-09-27T09:50:22+00:00October 30th, 2015|Sustainability, Sound Proofing|