A Simple Experiment to Explore Standing Waves in a Flexible Corrugated Sound Tube

Abstract

Sound tubes, pipes, and singing rods are used as musical instruments and as toys to perform amusing experiments. In particular, corrugated tubes present unique characteristics with respect to the sounds they can produce; that is why they have been studied so intensively, both at theoretical and experimental levels.1–4 Experimental studies usually involve expensive and sophisticated equipment that is out of reach of school laboratory facilities.3–6 In this paper we show how to investigate quantitatively the sounds produced by a flexible sound tube corrugated on the inside by using educational equipment readily available in school laboratories, such as the oscilloscope, the microphone, the anemometer, and the air pump. We show that it is possible for students to study the discontinuous spectrum of sounds produced by a flexible corrugated tube and go even further, computing the speed of sound in air with a simple experimental procedure.

Measuring the speed of sound with a pan flute and a smartphone: a half-melodic and totally-didactic experiment

“…In this work, we use the sound produced by the pipes of a pan flute and a smartphone to obtain the speed of sound in the air. Other similar works have been published such as [21][22][23][24][25][26][27][28]. In this manuscript, we analyse why the obtained speed of sound differs a little bit from the one obtained with thermodynamic calculations.…”

The speed of sound in singing tubes

“…All these values agrees fairly well within our uncertainties with the reference value for the speed of sound in still air at our laboratory conditions (P = 9.74 × 10 4 Pa, T = 298 K), which is 347 m s −1 . The need to correct the speed of sound inside the corrugated pipe, as shown in this article, is not a negligible point, at least if one wants to properly compare observed and reference values and not to ascribe possible discrepancies, for instance, to other effects, such as temperature dependences [7].…”

The monster sound pipe

“…Popular corrugated toy tubes that are twirled to obtain sounds have been around for decades [2][3][4][5]. The corrugated drainage pipe is a 'monster' version of the toy tube.…”