Lab: Measuring the Speed of Sound in Air (with uncertainty analysis)

Although many versions of this lab exist, this version written by Peter Bohacek includes uncertainty analysis consistent with effective measurement technique.

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This material was originally developed through comPADRE
as part of its collaboration with the SERC Pedagogic Service.

Initial Publication Date: November 4, 2009

Summary

Students use a microphone and Vernier LabQuest to record the sound of a finger-snap echo in a 1-2 meter cardboard tube. Students measure the time for the echo to return to the microphone, and measure the length of the tube. Using their measurements, students determine the speed of sound. While other authors have produced similar labs, this version includes uncertainty analysis consistent with effective measurement technique as presented in the module Measurement and Uncertainty.

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Learning Goals

Goals for this lab include:

  • Students gain experience with Vernier LabQuest and LoggerPro
  • Students use effective measurement technique to determine the range of certainty of their lab results
  • Students experience measuring the time of a short-duration event, the time for a sound pulse to travel 2-4 meters
     

Context for Use

This lab is intended for use as part of a unit on the physics of sound in an introductory high school or college physics course. The sections on uncertainty and error analysis use concepts presented in the module Integrating Measurement and Uncertainty into Science Instruction. Data collection is quick -- 15 minutes -- once students get the hang of snapping their fingers and recording the sound. The entire lab (excluding calculations, which can be assigned as homework) can be completed in one 50 minute class period.

Description and Teaching Materials

Materials (for each lab group):

  • Cardboard tube 10-20 cm diameter, 1-2 meters long (home improvement stores often give these to teachers for free )
  • Vernier LabQuest or similar data colletion lab interface
  • Microphone to connect to lab interface
  • Meter stick

It takes students a little practice to snap their fingers loudly and clearly to trigger data collection and produce clear spikes on their graphs. It is recommended that the teacher practice before hand to master the technique.

PDF version Lab - speed of sound in pipe with uncertainty (Acrobat (PDF) 223kB Aug31 09)
Microsoft Word version Lab - speed of sound in pipe with uncertainty (Microsoft Word 157kB Aug31 09)

Teaching Notes and Tips

This version of this labs differs from others of its kind in that students are not asked to calculate the percent error between their value and the actual vale of sound. Instead, students determine the range of uncertainty of their result and compare this range to the accepted value. For additional information about this approach see How to Integrate Measurement and Uncertainty


Assessment

Lab instructions include questions and calculations that can be used to assess student work.

References and Resources