The Sound of Trigonometry

Students filtered into class after lunch and spotted my device at the front of the classroom.

They wandered towards it and noticed a green line rapidly bouncing up and down on the screen.

More students arrived to the calculus class and quickly came to the conclusion that the movement of the green line was not random and it was affected by their voices.

I explained that they were looking at a virtual oscilloscope that was measuring sound. The y-axis represents the voltage of the sound and the x-axis shows time.

The students thought this was 'cool' but couldn't see how this related to what we were learning about - graphing trigonometric functions (AS91575). In particular, we had been learning about the amplitude and frequency of sine and cosine waves.

The next step was opening the online tone generator and investigating how different frequencies and volumes were measured by the virtual oscilloscope. After a bit of tinkering, we found that an increase in volume caused an increase in amplitude (the wave's height above and below the x-axis) and an increase in the frequency of the sound led to a smaller period - squashing the wave. This was consistent with what we had been learning in class about the amplitude and frequency of sine and cosine waves.

Next time...

This was a last minute idea that I wanted to use as a starter activity to demonstrate how trigonometric functions are applied in real life. The class was buzzing during the activity and next time I would like to make this into a full lesson and give the students more opportunity to individually experiment with the tool.

The online tone generator was great at producing sine and cosine wave but the sound of trigonometry quickly became abrasive and headache inducing. It would be interesting to get students to analyse music of their choice - modelling parts of songs with trigonometric functions.