An inexpensive teaching laboratory apparatus for measuring the speed of sound and more

One of the laboratory experiments in our general education acoustics class is a measurement of the speed of sound activity. The apparatus for this activity consists of a pair of ultrasonic transducers, a signal generator, and an oscilloscope. Each transducer is mounted on a custom base that is designed to rest on top of a standard meter stick which lays flat on the lab bench. The bases are arranged on the meter stick such that the transducers face each other. One of the transducers is driven by the signal generator at its resonance frequency, creating a sound wave which is detected by the other transducer. By monitoring the relative phase of the transmitted and detected sound wave signals, an accurate measurement of the wavelength of the sound can be obtained. From the wavelength measurement and the drive frequency students easily calculate the speed of sound in the room. With the advent of 3D printing and the availability of inexpensive signal generators and oscilloscopes, this apparatus is affordable not only for colleges but also to many high schools. Furthermore, the apparatus can be also used to explore other wave phenomena, such as reflection, absorption, and interference.