Axtell's Notes: June 14

First job today was a program that would graph the .wav file as time/amplitude (as opposed to frequency/amplitude as in an FFT) It was simple enough to plot the float values from the raw data of the audio file, but there was a lot of spill.

a440 Sine Curve Points

Using a simple a440 file (one sustained note) a sine curve can be seen, but there is a lot of spill. I wrote a method that goes through each point and of the 5 points either way in the x-axis, it finds the closest and draws a line between those two points and only draws the lines and no points.

a440 Sine Curve Without Spill

a440 With A Partial At 880

There is still some odd spill, but not nearly as much and the curve is very clear. That option is now available from the menu in FFTGraph.

I figured out that the FFT graph prints a range of 0 to 22 MHz. With a little math, the FFTGraph window now prints the frequency with the highest amplitude in the corner of the screen.

Next I worked on turning everything I had into a GUI. Eventually if the mouse hovers over the graph the GUI will show the frequency at that point, and if the mouse clicks on the graph while comparing it will cycle through each graph.

Having never written my own GUI from scratch before, a lot of time was spent in working out how to use what I already had in a GUI. The GUI now works minimally. The FFTGraph class still provides a lot more useful information. Also, the GUI image will not scale when the window changes size.

Blank GUI Screen

GUI Showing an a440 FFT

GUI Showing an a440 FFT Comparison

There is a lot more to do with the GUI just to get it caught up with the FFTGraph class, then I'll look at adding Tayloe's WaveSplitter class so the files are of a more useful length, and then we'll move on to the constant Q transform.

I also still need to figure out how to get the raw data from the FFT into amplitude in decibels.