90 - Helmholtz Resonator

The goal if this experiment is to measure the speed of sound by using a simple universal Helmholtz Resonator, made from a bottle with different water levels. By blowing over the bottle’s neck and exciting the resonance frequency, it is possible to extract the resonance frequency as a function of filling level. Using the Helmholtz Resonance Equation, the speed of sound can be extracted.

Requirements:

• An empty bottle (glass, plastic) which should be as close as possible to two cylinders
• A smartphone/tablet with the possibility to record acoustic spectra (e.g. using the PhyPhox-App)
• A scale or water meter
• A ruler to measure the dimensions of the bottle