ClassPad Report - Fast Fourier Transform

ClassPad Report

Fast Fourier Transform

Enjoy my piano and guitar sound!

This is a simple experiment to analyze sound and understand how to use Fourier in real life. My daughter plays Piano. I play Guitar. The sound from each is different. Where is the difference? When we wish to analyze the sound, we handle over 1000 pieces of data and lots of calculations. Discrete mathematics shows us a way to do this, and technology enables us to study the calculations.

I use the CASIO EA200 to collect the data and the ECON software for ClassPad.
ECON software is free on CASIO's website.
ClassPad.net

Install ECON Software

The EA200 has a microphone for collecting sound data, and an FFT function to analyze it.
The ECON software for the ClassPad controls the EA200, transfers the FFT result from the EA200 to the ClassPad, and graphs it.

We have the activities for Fourier series and Discrete Fourier Transformation made with Spreadsheet. Those activities show the basic algorithm to understand Fourier with a small number of data. This activity shows one interesting use of FFT with real life data.

1st Step: Setup EA200

Tap E-ConEA200 on the ClassPad and set Sensor as Microphone-FFT.

Set the Frequency Pitch to 2Hz and Frequency Max for 2000Hz.

2nd Step: Collect Data and Draw FFT Graph

This is not my daughter who plays Piano. She's a student at college and is living there.
This is Mr. Gon! He is sitting in front of the Piano instead of my daughter and is thinking about how to play a beautiful song.

Anyway let's connect EA200 to the ClassPad and play the Piano!

Turn on EA200 Power S.W. and tap the data transfer button.

Play the Piano and then tap OK right away. The sampling period is very short so if you fail to catch the sound, try it again. The EA200 beeps after collecting data and then takes time analyzing it with FFT.

3rd Step: Research Piano Sound

This is the result of pressing piano key G5. EA200 gives a power spectrum graph. The frequency of each spectrum can be found by tracing the function with the pen and cursor.

I only played G5 on the keyboard, but the analysis shows that it contains another frequency. Key G5 is organized with several other frequencies: 388, 1166, 1558 HZ, and other smaller ones. It's easy to understand, because G5 creates the basic note and other frequencies give the tone.

I need to call the tuner before my daughter comes back from College for summer vacation because the frequency of each key isn't correct!

Low and High Key

These are the results for A2, A4, A5 and A6. When I play A2, the sound has many other frequencies near A2 in the tone. When I play A6, there are not other frequencies around A6. I guess this is the reason why high keys sound clearer.

Continue to Part 2