# gst: intentional defects to trap confined acoustic modes that are protected from perturbation

AA << has discovered how to exploit certain defects to protect confined energy in acoustics systems. Their experimental approach provides a versatile platform to create at-will defects for further theoretical validation and to improve control of waves in other systems, such as light >>

<< We set to understand whether topological defects, such as disclinations, can be created to trap highly confined acoustic modes that are protected from perturbation, (..) Our core insight was that, if we consider the point group symmetry of the disclination, a pair of disclinations modes are prevented from pairing away from zero frequency. This protection mechanism results from the interplay of the symmetry-protected topological phase of the crystalline lattice and the topological charge and symmetry of the disclination. >> Wladimir A. Benalcazar.

<< This is the first work experimentally validating that such protected states exist in the disclination core, >> Yun Jing. 

️

Ashley J. Wennersherron. Researchers find imperfections provide protection for system symmetry. Penn State College of Engineering. May 20, 2022.

https://phys.org/news/2022-05-imperfections-symmetry.html

Sarah Wells. Symmetrical Binding for Topological States. Physics 15, s56. Apr 26, 2022. 

https://physics.aps.org/articles/v15/s56

Yuanchen Deng, Wladimir A. Benalcazar, et al. Observation of Degenerate Zero-Energy Topological States at Disclinations in an Acoustic Lattice. Phys. Rev. Lett. 128, 174301. Apr 26, 2022. 

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.128.174301

Also

keyword 'acoustic' in FonT

https://flashontrack.blogspot.com/search?q=acoustic

Keywords: gst, acoustics, acoustic metamaterials, symmetry, system symmetry, imperfection, defect, topological defects, disclination

# astro: going beyond a performance by Frank Zappa (or a speech by – for example – a political entity), two speeds of sound found on Mars

AA << find that atmospheric sounds extend measurements of pressure variations down to 1,000 times smaller scales than ever observed before, revealing a dissipative regime extending over 5 orders of magnitude in energy. Using point sources of sound (Ingenuity rotorcraft, laser-induced sparks), (AA) highlight two distinct values for the speed of sound that are ~10 m/s apart below and above 240 Hz, a unique characteristic of low-pressure CO2-dominated atmosphere. (They) also provide the acoustic attenuation with distance above 2 kHz, allowing to elucidate the large contribution of the CO2 vibrational relaxation in the audible range. >>

Maurice, S., Chide, B., Murdoch, N. et al. In situ recording of Mars soundscape. Nature. doi: 10.1038/ s41586-022-04679-0. Apr 1, 2022. 

https://www.nature.com/articles/s41586-022-04679-0

<< All of these factors would make it difficult for two people to have a conversation only five meters (16 feet) apart >> Sylvestre Maurice.

Juliette Collen and Daniel Lawler. First audio recorded on Mars reveals two speeds of sound. Phys.org. Apr 1, 2022. 

https://phys.org/news/2022-04-audio-mars-reveals.html

NASA Perseverance Rover Captures 

Puff, Whir, Zap Sounds from Mars 

https://youtu.be/lX5iVyfF3N0

Also

Frank Zappa 

https://www.zappa.com/

image from  

https://www.zappa.com/sites/g/files/aaj776/f/styles/suzuki_breakpoints_image_tablet_16x9/public/news/202104/Zappa88-Home-banner-03.jpg

keywords: astro, mars, acoustics, sound, speed of sound, dissipative regimes, music, jazz, freejazz