Digital Sound & Music: Concepts, Applications, & Science, Chapter 2, last updated 6/25/2013
Figure 2.44 440 Hz, /6 phase offset
Now we add the three sine waves to create a composite wave that has three frequency
components at three different phases.
a = (x + y + z)/3;
Notice that we divide the summed sound waves by three so that the sound doesn‟t clip. You can
graph the three-component sound wave with the following:
plot(t, a);
axis([0 0.05 -1.5 1.5]);
title('a = x + y + z');
Figure 2.45 Time domain data for a 3-component waveform
This is a graph of the sound wave in the time domain. You could call it an impulse response
graph, although when you‟re looking at a sound file like this, you usually just think of it as
“sound data in the time domain.” The term “impulse response” is used more commonly for time
domain filters, as we‟ll see in Chapter 7.
You might want to play the sound to be sure you have what you think you have. The
sound function requires that you tell it the number of samples it should play per second, which
for our simulation is 44,100.
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