Find out the frequency of your Helmholtz resonator.
The resonance of air flowing over a cavity of air deviates, depending on the size of the cavity and the amount of fluid it's filled with -- which determines the amount of air in the space. Using these variables, German physicist Herman Helmholtz penned down an equation for determining the frequency of the resonating air. Helmholtz' equation is handy for fine-tuning the pitch of musical bottles or building a science fair project. Set up your own Helmholtz resonator experiment, using his equation and a few household items.
Instructions
1. Fill up a measuring cup to its highest measuring mark. Pour the measuring cup's water into a water bottle, until the water level reaches the base of the bottle's neck.
2. Subtract the amount of water remaining in the measuring cup from its original amount to figure out how much water was poured into the bottle.
3. Measure the diameter of the neck, and then multiple the value by pie to find out the neck's area. Measure the length and radius of the bottle's neck, and then multiply the length by 1.5 times its radius. Write down the volume of the bottle from the measurement on its label or inscribed on its bottom.
4. Use your calculator to multiply the bottle's volume times the effective length of the neck. Divide the area of the neck by the product, and then find the square root of the product.
5. Refer to a Predicted Average Peak Expiratory Flow (PAPEF) chart found online, to get a rough average of the volume of air you exert from your lungs. Divide the speed of air exerted from your lungs by two time pie. Then multiply the quotient times the square root of your result from Step 4 to find out the natural frequency of your Helmholtz resonator.
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