Demonstrating Sound Wave Propagation with Candle Flame and Loudspeaker
A still frame of a candle flame motion in front of a sinusoidally driven loudspeaker cone (on the left).
The experimental setup.
“Barely shaking” mode is the smallest distinctively observable flame motion. Flame bifurcation is just noticeable in this still picture.
Longitudinal oscillation of a flame—the sought-after instructional situation.
Bifurcated flame with peak-to-peak amplitude ≥ 2 mm.
“Longitudinal with leaning” mode of the flame behavior.
“Leaning” mode of the flame behavior (close-up of Fig. 1 with superimposed ruler).
Amplitude-frequency loudspeaker input with corresponding areas of different flame behaviors.
Simultaneous effect on flames in front of the top and the bottom part of the loudspeaker at 67 Hz and 5.8 V.
The simultaneous effects on flames laterally positioned in front of the right and left side of the loudspeaker at 38 Hz and 6.3 V.
Candle in front of a loudspeaker.
The loudspeaker membrane shape can be easily changed (left) and a “smoke detector” (right) introduces a range of new options for observation.
Lowest amplitudes at which different flame behavior modes appear, at each of the specified frequencies.
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