Main Question or Discussion Point
i'm doing an experiment to study the effect of sound waves on fire and smoke and would like to know how can i produce sound waves with frequencies varying from 0-200 hz
Anorlunda. I originally thought you were wrong that a small hole could produce low frequency sound radiation when it is only a small fraction of a wavelength in diameter. But sound is a longitudinal wave and, unlike a loud speaker, the rear of the "piston". which would radiate cancelling radiation, is not open. But it still leaves me wondering, because as receiver of sound, I cannot yet believe that a small hole will be an efficient receiver of energy.
Those big refrigerator size speakers that they use at rock concerts do a good job over much of that frequency range, but not down to 0 hz.
Better still would be a stream of compressed air with a rotating disc with holes in front of it. With that you can adjust:
For exactly zero hertz, take away the disc and blow air directly on the fire. But if you tell the guys in the firehouse that you need to study that, you'll be laughed out of the house and never invited back. Shame on you for writing 0 hz in the OP.
- The pressure of the compressed air
- The flow rate of the compressed air
- The frequency by changing the disc speed and also by varying the number of holes in the disc.
- You can make the whole thing portable and you can aim it and vary the distance to the fire.