One can then communicate the idea of filtering low or high frequencies by separating and dropping only the basketball or tennis ball respectively. Their combined bounce represents a rapid change from low to high (spatial) frequencies indicating an edge, as in rapidly going from dark to light or vice versa (rapid tonal contrast as edge). The basketball, having a lower bounce represents low frequencies, while the tennis ball with its higher bounce represents high frequencies. A non-computer activity to assist in explaining this relationship could be a physical demonstration followed by a discussion.įor example, one could place a tennis ball on top of a basketball, let them drop, and discuss the combined bounce. Of these three, the concept most difficult to grasp is edge detection, which interprets edges as high spatial frequencies within an image.
Finally, Gimp explores spatial frequency and edge detection, resulting in various filters users can see and apply first hand. Sonic Visualiser explores spectrograms and the idea of data visualisation.
In particular, three applications are demonstrated: Audacity, Sonic Visualiser, and Gimp.Īudacity explores how to read a basic spectrum plot, which in technical terms is a signal in the frequency or spectral domain. Part Two is intended to demonstrate basic, but important, audio and image editing applications, that we otherwise take for granted in our daily interactions with media. As stated in Part One, signal processing forms the foundation of the current multimedia revolution.