Low-Cost Sound-Based Flame Suppression A Classroom Study

A loudspeaker driven by a free frequency-generator app extinguished a small flame at low frequencies in the range 50–90 Hz. In a single trial at each frequency, the time to extinguish fell from 20 s at 50 Hz to 14 s at 90 Hz. This school-level study describes the build, the test method and the results, and discusses why the effect occurs. Sound travels through air as an adiabatic wave, but the temperature change in such a wave is far too small to cool a flame, so we propose that the air movement caused by the sound separates the flame from its fuel vapour and oxygen.