From speed of sound to vapour pressure: an undergraduate school experiment as an example of systematic error research

Abstract

Abstract This article presents an undergraduate project for measuring the speed of sound in the air as a function of air temperature. The measurement is implemented in two versions. The simplicity of the basic experiment in dry air is used for a detailed analysis of systematic errors: the measured values are corrected with an additive constant and optimized to match the expected parabolic dependence of the speed of sound on temperature. Such a time correction is correlated with the physical content, that is, by changing the phase of oscillation of the pressure difference at the reflection of the sound at the open end of the tube. The second part of the experiment involves measuring the speed of sound in saturated humid air as a function of air temperature and allows for a substantive connection of two areas of physics (waves and thermodynamics). The measured water vapour pressure, within the range of statistical errors, follows the theoretical course up to the upper limit of the measured temperature range (60 °C) surprisingly well.