DIY small scale resonance tube for measuring the speed of sound in air

摘要

This research invented a small scale with no cost experimental set to determine the speed of sound in the air by resonance method. Equipment consisted of a bubble tea straw with label measuring scale, a full plastic water bottle and the n-Track Tuner (iOS) or Guitar Tuner (Android) application for generating sound waves. Sound waves were sent down a bubble tea straw filled with an air. The waves reflected back up the straw from a water surface and interfered with the waves traveling downward. By properly adjusting the water level, a resonance condition could be established. By knowing the frequency of the sound wave and the position of the water level for two different resonant lengths, the speed at which sound waves travel through the air was found. In this experiment, the frequency was specified 1, 500 Hz at 24.00 °C, 26.00 °C and 30.00 °C respectively. The sound speed which was calculated was 345.0, 347.0 and 349.0 m/s respectively. The standard value of sound speed at the same temperature was 345.4, 346.6 and 349.0 m/s respectively. The percent error value of the sound speed was calculated to compare with the standard value of sound speeds was 0.1%, 0.1% and 0.0% respectively. This an experiment was effective and could be efficiently used in educational physics. Moreover, it is easy to use, low cost, and portable. Students can also prepare the equipments themselves.