Defense Advanced Research Projects Agency (DARPA) is showing off a new system that can put out flames using only sound [1]. It’s part of the U.S. defense agency’s Instant Fire Suppression program. Using two speakers arranged on either side of a pool fire, an acoustic field was emitted and engulfed the flame. The sound increases air velocity, which thins the boundary layer of the flame, making it weak and much easier to douse. “We have shown that the physics of combustion still has surprises in store for us” commented DARPA manager Matthew Goodman in a statement. “Perhaps these results will spur new ideas and applications in combustion research”. Lest you think this is really surprising, here are a couple of earlier mentions of the concept.
First, a Google search leads quickly to the Wikipedia entry for Charles Kellog [2] which cites the following from a 1926 newspaper article: “In The Sydney Morning Herald, Thursday, February 4, année 1926: Sound vibration – Extinguishes Fire: New-York, Feb. 2. 1926: Mr Charles Kellogg, a Californian scientist, give firemen here a demonstration of extinguishing a gas flame two feet high by tonal vibration. Mr Kellogg passed a bow, like an enlarged violin bow, swiftly across an aluminium tuning fork, producing a screech like an intense radio static. Instantly the yellow flame subsided to six inches and became a sputtering blue flare. Another movement of the bow completely extinguished the flame. Mr Kellogg claimed that in future buildings would have a scientifically-determined pitch, with a screech for extinguishing fires tuned in from a central firehouse, where it would be produced by a much larger bow. He said that the General Electric Company was experimenting with the matter”.
Second, from a book The Theory of Sound published in 1896 by Lord Rayleigh, 1904 Nobel Prize winner for Physics [3]: “Singing flames may sometimes replace electrically maintained tuning-forks for the production of pure tones, when absolute constancy of pitch is not insisted upon. In order to avoid progressive deterioration of the air, it is advisable to use a resonator open above as well as below. A bulbous chimney, such as are often used with paraffin lamps, meets this requirement, and at the same time emits a pure tone. Or an otherwise cylindrical pipe may be blocked in the middle by a loosely fitting plug (Phil. Mag. vol. vii. p. 149, 1879).
Vibrations capable of being maintained are not always self-starting. The initial impulse may be given by a blow administered to the resonator, or by a gentle blast directed across the mouth. In the striking experiments of Schaff’gotsch and Tyndall (Sound, 3rd edition, p. 224, 1875) a flame, previously silent, responds to a sound in unison with its own. In some cases the vibrations thus initiated rise to such intensity as to extinguish the flame.”
by Jack Watts. Fire Safety Institute, USA, and Associate Editor of Fire Safety Science News REFERENCES 1. Video: Darpa’s ‘Wall-of-Sound’ Fire Extinguisher, Wired, July 13, 2012. http://www.wired.com/
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Bronwyn Forrest is a 3rd year PhD student at the University of Waterloo, conducting multi-disciplinary research investigating human physiological response to fire exposure. Bronwyn graduated in 2017 with a BSc. Honours Kinesiology and in 2020 with a MASc. Mechanical & Mechatronics Engineering (Heat Release Rate in Ventilation-Limited Furniture Fires) before merging her two degrees in her PhD research. As a senior graduate student in the Fire Research Group, Bronwyn spear-heads large-scale fire experiments, mentors junior graduate and undergraduate students, and has recently set-up a new ‘human exposure lab’ at the Fire Research Facility where she leads new research in that area. Since her induction into the world of fire science, Bronwyn has grown more and more passionate about the multi-faceted nature of emerging fire safety challenges. Through innovative research, she hopes to make meaningful contributions that help shape changes to fire safety over the course of her career.
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Brian J. Meacham, PhD, PE (CT&MA), EUR ING, CEng (UK), FIFireE, FSFPE, is the Managing Principal of Meacham Associates. He develops risk-informed performance-based solutions to complex building and infrastructure challenges, provides peer-review services, and undertakes building and fire regulatory system studies. He also conducts research in these areas as well as in sustainable and fire resilient built environments and fire safety technologies. Brian has authored more than 300 publications, given more than 300 presentations and has been awarded more than $4M in research funding. His prior positions include Associate Professor of Fire Protection Engineering at Worcester Polytechnic Institute, Principal at Arup, Technical Director and Research Director at SFPE, and fire safety engineer in Europe and the USA. Brian is Chair of the ICC Performance Code Committee, Chair of the NFPA Technical Committee on Fire Risk Assessment Methods, Immediate Past Chair of the International Association for Fire Safety Science (IAFSS), a Past President of the SFPE, and a past Chair of the Inter-jurisdictional Regulatory Collaboration Committee (IRCC). He is a licensed Professional Engineer in CT and MA, a Chartered Engineer and Fellow of the Institution of Fire Engineers (UK), a registered European Engineer (EUR ING), a Fellow of the SFPE, and a Fulbright Global Scholar.
Kazunori Harada is a professor of architecture & architectural engineering at Kyoto University, Japan. He has a career in fire research for over 35 years. He has authored 14 IAFSS symposium papers. His expertise covers the fire resistance of construction materials, smoke movement and control, burning of combustibles in open and compartment, performance-based code & design of buildings and so on. He serves as a vice president of AOAFST, Asia-Oceania Association of Fire Science and Technology. He also serves as the Convenor of ISO/TC92/SC4 WG9, calculation methods for fire safety engineering (FSE), which develops calculation standards concerning FSE.
Dr Xinyan Huang is an Associate Professor at The Hong Kong Polytechnic University and the Deputy Director of the Research Centre for Fire Safety Engineering. He received his PhD from Imperial College London, MSc from UC San Diego, and BEng from Southeast University, and was a Postdoc at UC Berkeley. Dr Huang is a Combustion Scientist and a Fire Safety Engineer who has co-authored over 200 journal papers. He is an Associate Editor of Fire Technology and International Journal of Wildland Fire, an editorial member of J. Building Engineering, Fire Safety J. and Fire and Materials, a Chartered Building Services and Fire Engineer, a committee member for HK Fire Safety Code, and a Fire Expert for HK High Court. He receives the NSFC Excellent Young Scientists Fund, Bernard Lewis Fellowship and Sugden Best Paper Award from Combustion Institute, “5 under 35” and Bono Award from the Society of Fire Protection Engineers (SFPE).
Arnaud Trouvé is Professor and Chair in the Department of Fire Protection Engineering at the University of Maryland in College Park, USA. He joined the Faculty in 2001 with a Ph.D. (1989) and Engineering Degree (1985) from École Centrale of Paris, France, and with previous experience as a combustion research engineer. Professor Trouvé’s research interests include fire modeling and Computational Fluid Dynamics (CFD); application of data assimilation to fire and combustion; and physical modeling of combustion- and fire-related phenomena, including compartment fires, wildland fires and explosions. Professor Trouvé is a Fellow of the Combustion Institute and the recipient of the 2017 FORUM Sjölin Award. He has served on the editorial boards of the Proceedings of the Combustion Institute, Progress in Energy and Combustion Science, Combustion and Flame, and Fire Technology, and is currently on the editorial boards of Combustion Theory and Modelling and the Fire Safety Journal. Professor Trouvé is also a past Chair of the US Eastern States Section of the Combustion Institute (ESSCI) and a past Member of the Executive Board of the International Association for Fire Safety Science (IAFSS). He is a co-Chair of a recent initiative endorsed by IAFSS and called the “IAFSS Working Group on Measurement and Computation of Fire Phenomena” (the MaCFP Working Group) and the past Chair of a new network of leading higher-education institutions and research laboratories in fire safety engineering called the International Fire Safety Consortium (IFSC).
Dr Felix Wiesner is an Assistant Professor at the University of British Columbia and study the role of engineered timber in fire safety. I work in the Faculty of Forestry as part of the Wood Science department. My research focus has mostly been experimental, considering fire dynamics in timber compartments and the structural fire capacity of engineered timber products. In addition, I am interested in the performance of timber in exterior building or infrastructure setting. This closely interfaces with wildfire considerations for the wildland urban interface (WUI), especially when it comes to smouldering.
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ROGAUME Thomas is an Professor at the University of Poitiers – Pprime Institute (UPR3346 CNRS), FRANCE.
Yu Wang is a professor at the State Key Laboratory of Fire Science, University of Science and Technology of China (USTC). He got joint Ph.D. from USTC and the City University of Hong Kong in 2016 and had working experience at the University of Edinburgh, Worcester Polytechnic Institute and National University of Singapore before returning to China in 2020. His primary research areas are high-rise building fire and large outdoor fire. Yu has published over 50 SCI journal papers, and is currently an Associate Editor in Fire Technology and Editorial Board Member in Fire Safety Journal. He initiated the first English fire course at USTC, Introduction of Fire Dynamics, reported by China News and People’s Daily Online (over 260,000 audiences). In recent years, he has received SFPE Global 5 Under 35 Award, Youth May Fourth Medal (Anhui Province), Young Faculty Career Award (USTCAF), and some Best Paper/Presentation/Poster/Image Awards in IAFSS or AOSFST.
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Dr. Shuna Ni is an Assistant Professor in the Department of Fire Protection Engineering at the University of Maryland, College Park. She received her Ph.D. degree at Texas A&M University in 2018 and her Master’s degree at Tongji University in 2013. Dr. Ni’s research focuses on fire forensics, structural fire engineering, WUI fire resilience, fire safety of tall mass-timber buildings and fire-related multiple hazards. Her research has been funded by National Science Foundation, National Institute of Justice, Fire Protection Research Foundation, University Transportation Centers under the Department of Transportation, Grand Challenges Grants Program at the University of Maryland and industrial partners.
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