Stefanie Hövermann

The frequency of a sound produced by blowing into a bottle varies with the water level and thus the amount of air in a bottle. By filling bottles with different amounts of water and measuring the height ha of the air column, the air volume Va and the sound frequency f, the correlation between these parameters is investigated. Subsequently, diagrams of the measured values are plotted to find functional correlations. From these, a proportionality between the inverse of the height ha of the air column and the frequency f can be derived. This leads to an equation which can be used to calculate the mass of water required for each desired frequency.

Taking into account that the timbre of a sound depends on the spectrum of audible overtones, a subsequent experiment is conducted where the sounds are recorded and the resulting frequency spectra are analyzed. This shows that the proportion of audible overtones in identical bottles increases with the fundamental frequency, leading to a brighter sound and therefore affecting the timbre. The size of the bottle, however, has no relevant effect on the frequency spectrum.