# 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

# brain: brain images of silence

<< When imagining music, the musicians' brain activity had the opposite electrical polarity to when they listened to it -- indicating different brain activations -- but the same type of activity as for imagery occurred in silent moments of the songs when people would have expected a note but there wasn't one. >>

<< There is no sensory input during silence and imagined music, so the neural activity we discovered is coming purely from the brain's predictions e.g., the brain's internal model of music. Even though the silent time-intervals do not have an input sound, we found consistent patterns of neural activity in those intervals, indicating that the brain reacts to both notes and silences of music. Ultimately, this underlines that music is more than a sensory experience for the brain as it engages the brain in a continuous attempt of predicting upcoming musical events. Our study has isolated the neural activity produced by that prediction process. And our results suggest that such prediction processes are at the foundation of both music listening and imagery. >> Giovanni Di Liberto. 

The music of silence: Imagining a song triggers similar brain activity to moments of mid-music silence. Trinity College Dublin. Aug 3, 2021. 

https://www.sciencedaily.com/releases/2021/08/210803105600.htm

Guilhem Marion, Giovanni M. Di Liberto,  Shihab A. Shamma. The Music of Silence. Part I: Responses to Musical Imagery Encode Melodic Expectations and Acoustics. Journal of Neuroscience  JN-RM-0183-21. doi: 10.1523/ JNEUROSCI.0183-21.2021. 2 Aug 2, 2021.

https://www.jneurosci.org/content/early/2021/07/23/JNEUROSCI.0183-21.2021.

Giovanni M. Di Liberto, Guilhem Marion,  Shihab A. Shamma. The music of silence. Part II: Music Listening Induces Imagery Responses. Journal of Neuroscience JN-RM-0184-21. doi: 10.1523/ JNEUROSCI.0184-21.2021. 

Aug 2, 2021.

https://www.jneurosci.org/content/early/2021/07/22/JNEUROSCI.0184-21.2021

Also

2123 - le dislocazioni pausali di Theo. 

(quasi-stochastic poetry). Notes. Feb 26, 2007.

https://inkpi.blogspot.com/2007/02/2123-le-dislocazioni-pausali-di-theo.html

A pause (acyclic pauses?)  approach to enhance and manage creativity. Mar 23, 2019.

https://flashontrack.blogspot.com/2019/03/brain-pause-acyclic-pauses-approach-to.html

We pronounce words more slowly compared with verbs and sometimes pause. May 20, 2018.

https://flashontrack.blogspot.com/2018/05/lang-we-pronounce-words-more-slowly.html

# 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

# gst: apropos of discomfort tolerances, maximize a sweet spot (of a sound zone)

AA << considered the sweet spot as the region where the a sound scene is psycho-acoustically close to a desired auditory scene. >>

They << developed a method (SWEET-ReLU algorithm) that generates a sound scene that maximizes this sweet spot while guaranteeing no discomfort over a spatial region of interest. (..) the sweet spot and the discomfort tolerance can be modeled within a flexible monaural psycho-acoustic framework. >>

Pedro Izquierdo Lehmann, Rodrigo F. Cadiz, Carlos A. Sing Long. Maximizing the Psycho-Acoustic Sweet Spot. arXiv: 2201.01461v1 [eess.AS]. Jan 5, 2022.

https://arxiv.org/abs/2201.01461

Keywords: sound, psycho-acoustics, discomfort tolerance