Rodolfo Venegas

CREDENTIALS

  1. R. Venegas, “Microstructure Influence on acoustical properties of multi-scale porous materials,” PhD Thesis, University of Salford, UK, 2011.
  2. R. Venegas and O. Umnova, “Acoustical properties of double porosity granular materials,” J. Acoust. Soc. Am. 130 (5), pp. 2765-2776 (2011).
  3. R. Venegas and O. Umnova, “Acoustical properties of packings of porous grains,” 3rd Symposium on the Acoustics of Poro-Elastic Materials SAPEM 2011, Dec. 14-16, Ferrara, Italy, 2011(Invited paper).
  4. S. Floody and R. Venegas, “Differential evolution applied to room acoustic optimisation,” IX Congreso de la Sociedad Chilena de Investigación Operativa OPTIMA 2011, Oct. 26-29, Pucon, Chile, 2011.
  5. S. Floody, R. Venegas and F. Leighton, “Optimal design of slit resonators for acoustic normal mode control in rectangular rooms,” COMSOL Conference, Nov. 17-19, Paris, France, 2010.
  6. S. Floody and R. Venegas, “Shape optimization of polygonal rooms based on spatially homogeneous sound field distribution and psychoacoustic criteria at low frequencies,” Euronoise 2009, October 26-28, 2009, Edinburgh, UK.
  7. S. Floody and R. Venegas, “Room shape optimization for the correct normal modes distribution at low frequencies based on psychoacoustic criteria,” Revista de Sonido y Acústica, 3 (3) pp.28-34 (2008).
  8. S. Floody and R. Venegas, “Shape optimization of polygonal rooms for a correct modal distribution at low frequencies based on psychoacoustic criterion, Acoustics’08, June 29 - July 04, 2008, Paris, France.
  9. S. Floody and R. Venegas, “Shape optimization in rectangular rooms for a correct modal distribution at low frecuencies based on psychoacoustical model,” XVI Congress on Numerical Method and their Applications ENIEF 2007 and I Congress on Computational, Industrial and Applied mathematics MACI 2007, Cordoba, Argentine, October 02-05, 2007.
  10. R. Venegas and J. Undurraga, “In situ evaluation of sound insulation using transfer function measurements,” 19th International Congress on Acoustics ICA Madrid 2007, 2-7 September, 2007, Madrid, Spain. (Invited paper)
  11. J. Undurraga and R. Venegas, “Continuous reverberation time estimation applied to obtain normalized sound level differences,” 19th International Congress on Acoustics ICA Madrid 2007, 2-7 September, 2007, Madrid, Spain.
  12. R. Venegas, M. Nabuco, P. Massarani, “Sound insulation evaluation using transfer function measurements,” Building Acoustics, 13 (1),pp. 23-31(2006).
  13. P. Massarani, M. Nabuco and R. Venegas, “Level adjustment for multi-channel impulse response measurements in building acoustics,” 34th Internoise, International Congress and Exposition on Noise Control Engineering, 7-10 August 2005, Rio de Janeiro, Brazil.
  14. R. Venegas, M. Nabuco, P.Massarani, Sound Insulation evaluation using Transfer Function Measurements,” 34th Internoise, International Congress and Exposition on Noise Control Engineering, 7-10 August 2005, Rio de Janeiro, Brazil.
  15. A. Boardman, O. Umnova, A. Elliot, and R. Venegas, "Membrane acoustic metamaterials for ear defenders with low frequency capability," Research report for DSTL, 2013 (in preparation).
  16. O. Umnova, A. Elliot, J. Coakley, and R. Venegas, "A graded-index omnidirectional acoustic absorber," Research report for DSTL (Contract No DSTLX1000063985), 2012.
  17. R. Venegas and O. Umnova, "Numerical modelling of sound absorptive properties of double porosity granular materials," COMSOL Conference, Nov. 17-19, Paris, France, 2010.
  18. R. Venegas and O. Umnova, "Acoustics of porous media: A tortuous history," XIII Encuentro Internacional de Acustica SEMACUS 2010,Oct 1-2, Santiago, Chile, 2010 (Plenary Lecture).
  19. R. Venegas and O. Umnova, "Sound propagation in multi-scale porous materials," XIII Encuentro Internacional de Acustica SEMACUS 2010,Oct 1-2, Santiago, Chile, 2010 (Plenary Lecture).
  20. O.Umnova, R. Venegas and A. Krynkin, "Effective medium models for acoustic materials," Tyndall medal lecture, IoA conference: Noise in the built environment, April 29-30, 2010, Ghent, Belgium.
  21. R.Venegas and O. Umnova, "Effective acoustical properties of random microfibrous materials," Euronoise 2009, October 26-28, 2009, Edinburgh, UK.
  22. O. Umnova, R.Venegas and F. Bechwati, "Acoustical properties of microporous granular materials," Euronoise 2009, October 26-28, 2009, Edinburgh, UK.
  23. R.Venegas and O. Umnova, "Acoustical properties of random arrays of micro cylinders," 1st International Conference on challenges of porous media, March 11-14, 2009, Kaiserslautern, Germany.
  24. O. Umnova, D. Tsiklauri and R. Venegas, "Effect of boundary slip on the acoustical properties of microfibrous materials," Journal of the Acoustical Society of America, 126(4), pp.1850-1861 (2009)
  25. R.Venegas and O. Umnova, "Acoustical properties of disordered arrays of circular cylinders," SAPEM 2008, December, 17-18-19, Braford, UK.
  26. R. Venegas and O. Umnova, "On the influence of the micro-geometry on sound propagation through periodic array of cylinders," Acoustics’08, June 29 - July 04, 2008, Paris, France.
  27. O. Umnova, D. Tsiklauri and R. Venegas, "Influence of boundary slip on the acoustical properties of microfibrous absorbents," Acoustics’08, June 29 - July 04, 2008, Paris, France.

John Coakley

CREDENTIALS

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THE INNOVATION FORUM
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Research and Development in Acoustic Materials, Noise Control, Audio and Air Suspension

including

Noise absorbers and barriers, acoustic panels and sound deadening materials for vehicles and buildings, exhaust silencers, mufflers, membrane metamaterials and hearing defenders

Audio design for loudspeakers, subwoofers and headphones, acoustic room treatments and design for recording studios and home theatres

Lower spring rate air springs, gas struts, tyres and components for air suspension.

ways of working with us

Collaboration

We’re always on the look-out for collaborative partnerships with industry and academia and have developed a range of models for engagement to suit each client, from revenue sharing agreements, licensing, sector-specific exclusive collaborative agreements to full venture partnering.

So what makes Carbon Air technologies special?

It’s all about porosity. And one amazing material in particular.

Consultancy

Carbon Air is a certified consultant for Comsol Multiphysics software with access to the University of Salford’s acoustic laboratories.

Find out more about our work in t.he acoustics of porous materials, noise control, audio design and acoustic metamaterials

A Guide to
ACTIVATED CARBON

Activated Carbon is a wonder material

Each granule is riddled with thousands of channels and millions of chambers of differing shapes and sizes.

These chambers can “breathe in” extraordinary quantities of air

In fact the surfaces of all materials will do this to some small extent – but those inside activated carbon act like glue to air molecules.

This section will explain why.

When the atoms in a solid bond they tend to do so in an electrically balanced way. But on the surface, the bonds on the open sides are missing, leaving an electrical charge that gas molecules will want to react with.

sorbtion

This bonding is called “Chemisorption”, and naturally the higher a material’s surface area, the more chemisorption will take place. But this is only a small part of the story.

sorbtion1

Things get weirder.

“Physisorption” accounts for most of the effects seen in Carbon Air technologies and is much more significant in terms of the number of gas molecules captured, more reversible through changes in pressure and is much stranger.

The same open bonds that caused some of the gas molecules to stick to the surface of the solid will cause powerful short range repulsion to all the others. This results in a zone of near-emptiness immediately above the chemisorped gas molecule layer

Then a new phenomenon
comes in to play.

Very weak “Van der Waals” forces extend from the solid to attract gas molecules toward the surface. These longer-range attractive forces oppose the stronger but shorter-range electrical forces pushing them away. The result is a densely populated “comfort zone” for molecules hovering above the surface.

THE PACKING OF MOLECULES
INTO THIS COMFORT ZONE IS
CALLED “PHYSISORPTION”

These “herding” forces- the electric pushing one way, the van der Waals pulling the other- are actually quite weak against a flat surface.

But when the surface turns a corner and becomes two surfaces at right angles, these forces conspire to cause a more powerful packing effect at the junction.

As more planes intersect the gathering effect becomes more powerful.

If an enclosing chamber of the right dimensions is formed then the gathering effect can be spectacular. The space within can hold many times more gas molecules than if the walls weren’t there.

 

Why is activated carbon
so good ?

Activated carbon is made by baking organic materials (wood, coconut shell, peat, coal and others) until all matter is converted to carbon. It is then “activated”, usually by driving water vapour through the material at high temperature and pressure to excavate the former cell cavities, revealing a delicate and highly porous carbon skeleton featuring millions of microscopic pores.

The functional origin of these pores means they fall into an organised hierarchy with broad (mesoscopic) transport channels feeding smaller (microscopic) chambers which themselves feed into millions of miniscule (nanoscopic) ones.

This system, which evolved in the organic matter to supply nutrient to the plant cells, becomes a highly effective way of transporting gas molecules to the adsoptive micropore and nanopore chambers that take their place after activation.

 

THE END RESULT

A vessel filled with activated carbon will contain much more air than if the granules weren’t there.

But the excess molecules have been “captured” by the carbon so they don’t contribute to pressure.

As more air molecules are introduced into the vessel, some of these will also become captured by the carbon.

Pressure in the vessel wont rise as it should.

 

The air in the vessel behaves mechanically and acoustically as if it has a

far greater volume

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