Schottenbauer Publishing

Wednesday, July 29, 2015

What is Sound? The Problem of Averaging a Messy Graph

Graphs provide a unique perspective into the nature of music and sound. Graph-reading skills can be integrated into music classes, supplementing traditional science and math curricula. 

For example, consider the following two graphs, excerpted from Where Does Sound Come From? Volume 1 from Schottenbauer Publishing. These graphs shed light on a perplexing problem pertaining to averages.

Discussion Questions
  1. Does the graph suggest (a) the presence of wind, (b) random differences in gas pressure in the room, or (c) error of the measurement device?
  2. Is it accurate to state that the gas pressure is: (a) 99.8, (b) 99.825, (c) 99.85, (d) constantly changing?

Discussion Questions
  1. What are the initial maximum and minimum sound pressures in the graph?
  2. By the end of the graph, what are the maximum and minimum sound pressures?
  3. Using a solid line, trace the maximum values of the sound pressures.
  4. Using a solid line, trace the minimum values of the sound pressures.
  5. Is it appropriate to average the minimum and maximum values on this graph, in order to show the true sound pressure reading? Why or why not?

Additional graphs of sound pressure, gas pressure, wind speed, and physical vibrations (force) are available in the lab manual Where Does Sound Come From? Volume 1 from Schottenbauer Publishing. Students can use these measurements to understand the nature of sound, by comparing and contrasting graphs from 27 musical instruments, including strings, woodwinds, brass, and percussion, plus voice.

Additional Information