Instantaneous Measurement of the Speed of Sound in Air and Water Using Arduino

Although schools commonly teach that sound waves propagate faster in solids than in liquids and in liquids than in gases, there is no low-cost activity that allows students to investigate if this statement is true or not. Indeed, some existing techniques simply allow them to identify the speed of sound in air and its temperature dependence.^1–3 

In this work, we present a simple and low-cost experimental apparatus that allows the determination of the speed of sound in air and water. Arduino is a controller board that requires little user experience and that has been widely used in numerous teaching activities. In robotics, the open source electronic platform Arduino associated with an HC-SR04 sensor⁴ has commonly been used to obtain the distance between a sensor and an obstacle, allowing the study of movement.⁵ It can also measure the total time between ultrasonic wave propagation emission and reflection. This...