A Simple Fixed–End Kundt’s Tube to Measure the Speed of Sound in Air

A Simple Fixed–End Kundt’s Tube to Measure the Speed of Sound in Air

We designed, developed, and tested a simple, yet robust, device to measure the speed of sound in air.The apparatus is based on modified Kundt’s tube that maintains a fixed length, in which the frequencyof standing sound waves is to be determined electronically using a microcontroller board (Arduino). The system works by emitting sound waves, at different frequencies, that are to be detected at the opposite end of the tube. Resonance is detected by measuring the phase difference between the emitted and received waves. To improve the accuracy of the calculations, the frequency of the sound waves is varied several times. The whole process is carried out automatically by the apparatus, which calculates the speed of sound for each of the frequencies used. The instrument finally gives a read out of the average speed of sound for air under room conditions. The apparatus also monitors the temperature and it is also capable of measuring the length of the tube for calibration purposes. We plan expand the use of the device to other gases. An equipment such as this, can be used to find, for example, the ratio of the heat capacity of a gas at constant pressure to that at constant volume, a quantity that its useful in many chemistry calculations.