teaching machines

Seeing Waveforms

June 12, 2019 by . Filed under electronics, music, public.

This post is part of a series of notes and exercises for a summer camp on making musical instruments with Arduino and Pure Data.

Author Christopher Paul Curtis writes in Elijah of Buxton, “Believe some to none of what you hear and only half of what you see.” This wisdom applies equally well to gossip and physical sound. Our ears are easily tricked, and sometimes we need to see sound to make sense of it.

In this exercise, we will visualize the waveforms of pure frequencies using Pure Data’s array object. In particular, we will create a patch that looks like this:

An array is two things in Pure Data. First, it is a container that stores many numbers. Second, it is a graph of those many numbers.

Follow these steps to produce your patch:

Challenges

After you get your patch working, answer the following questions on a piece of scratch paper.

  1. How does the waveform change as the frequency changes?
  2. How can you tweak the patch so that every time you change the frequency the plot automatically updates?
  3. Imagine a wall. Imagine a high frequency sound wave being directed at the wall. Then, imagine a low frequency wave being directed at the wall. Why are we more likely to hear the low frequency sound on the other side of the wall?