Monthly Archives: August 2014

Assn 1: Found Systems

For my assignment I chose to play a sort of game of telephone. I provided the initial recording and instructed others to listen then repeat to the best of their ability the recording prior to their own.  The memory capacity of the average person made it so that the initial signal very quickly became distorted.

Assignment 1: Found Systems

In 1914 Marcel Duchamp produced his first “readymade” – artwork made from things he found lying around (bottles, shovels, a coat-rack, & cetera).  For this assignment you are going to use a readymade system – a signal processing system that you find lying around.  Your “found system” could be on the internet, in one of your classrooms, in your telephone…  It could be a photocopier, an online tool that transforms text or images, a toy that transforms sounds, etc.

Like Alvin Lucier’s I am sitting in a room, you are going to use this system over and over and until your original signal is destroyed.  Present each generation of the transformed signal so we can see/hear it evolve.

Your signal can be text, sounds, images, video – or something else.  Win big on the “concept” section of this assignment by thinking of something we didn’t see coming.

Post your documentation on the class website along with a little description of what you did.  Tag your post “Assignments” (see here for more details on posting to the site).  And enter a link to your post on blackboard.

Intro to SP4CP

00 what is a signal

A signal could represent the temperature of a river, as it fluctuates over time:01 river

In this example, temperature is the dependent variable.  Thats cuz the temperature depends on what time it is.  Time is the independent variable.  We graph the dependent variable on the Y axis, and the independent variable on the X axis.

Signals can also be sounds:

02 acoustic guitar

Look at this nice visualization of a sound wave.  03 soundwave copy

Here we see the amplitude of our signal varying over time.

Signals can also be images, like so:

04 image

In an image the dependent variable is color.  In a still image, color does not fluctuate over time (it stays the same, always and forever), but it does fluctuate over space.  In a flat image, space is two dimensional (width x height) – so this is a 2D signal.  The dependent variable, color, fluctuates over two independent variables – X position and Y position.

Sound, on the other hand, is one-dimensional – the dependent variable, amplitude, varies over only one independent variable, time.

In video, what we have is a series of still images, presented over time:

05 motion image (1)

So in motion images, we see color fluctuating over space and time.06 signal processing is

Systems transform signals.07 signal processing diagram

Signal processing makes use of calculus and linear algebra.  We will be working with Max, which does a lot of this math “under the hood” – but we will be looking at the theory to get an understanding of what’s going on.


07b math

Signal processing makes the world go round:08 cell phones + towers 09 plane

A common display of SP in the arts, guitar pedals:10 guitar

The guitar pedals is a system that transforms the audio signal coming out of the guitar.11 guitar-fx

Chaining systems together yields interesting results.12 guitar-fxxx

Nam June Paik chained together video processing systems to create innovative video art:

13 NJP



Now, do this, please:14 20140825-nextweek

3 ways to unlock a Max patch

1.  Click the Lock/Unlock button on the bottom-left of the patch window


2. Right-click or Control-click somewhere in the background of the Max patch.  Select “Edit” from the context menu that pops up.  Don’t click on an object in the patch or this trick won’t work.


3.  Hit Command-E or select “Edit” from the View Menu


Alvin Lucier – I am Sitting in a Room

01 lucier sitting

In this well-known piece Alvin Lucier elegantly demonstrates that any acoustic space is a system that processes sound.  In a room, sounds bounce off walls, ceilings, floors, and other reflective surfaces, producing standing waves.  These waves add harmonics and reverberation to the original sound.  The frequency of the added harmonics depends upon the distance that the sound waves travel between the various reflective surfaces (amongst other factors).  In many rooms the added harmonics and reverberations are so subtle that they go unnoticed – we don’t think of sounds in a room as being processed.  But in this piece Lucier reveals these subtle transformations in a very dramatic way.

In I am Sitting in a Room, the composer reads a text aloud whilst using a microphone to record his voice.  The recording is then played back in the room, and the microphone now records the sound of the playback occurring in the room.  This second recording has now gone through the room twice (once during the original reading and again during the playback), and the harmonics and reverberations from the room are accumulating.  The second recording is then played back and re-recorded, and the process repeats over and over.  With each iteration of the process more and more reverberation and harmonics accumulate, until eventually the composer’s voice is an unintelligible blur of gorgeous room-o-licious tone-clouds.  Glorious!

This piece also demonstrates the use of feedback in a system, but on a time-scale that is larger than what we might expect.  Feedback is used in filters and echo systems to produce effects that are immediately noticeable.  In this piece, the feedback accumulation is rather slow (with one cycle of the system feeding back once every 90 seconds or so), allowing us to hear the subtle transformation of each feedback cycle with much more detail.

In fact, I would say this piece is a prime example of feedback art.  Aside from generating the original source signal (the composer reading a text), the only procedure that is used in the work is to present the output of a system back to the input stage of that same system.


Here is a live performance of the piece:

And here is an interesting homage called “I am Sitting in a Video Room”:

This piece also demonstrates the slow accumulation of feedback through a system.  In this case the system is not an acoustic space, but is Youtube.  A video is uploaded to Youtube, resulting in compression artifacts, little glitches in the sound and image, that are usually not noticeable.  The Youtube video is then downloaded and re-uploaded, resulting in a second iteration of artifacts.  The process repeats and the artifacts accumulate until the images and sounds in the video are a computery scrambled-up nightmare.  Terrifying!

And then there’s this:

Mind = Blown.

While not a direct reference to Lucier’s piece, Search by Image, Recursively, Transparent PNG, #1 by Sebastian Schmieg is another great example of feedback art.  The artist starts off by uploading a blank image to Google’s search-for-similar-images service.  The first hit that results is then presented back to Google and a similar-image search is performed on that image.  Each iteration of the system produces an image that is slightly different from the last one*, creating a slowly transforming visual landscape.

* This feedback system could have resulted in a recursive loop rather than the linear progression we see in the video.  If a similar-image search for image A produces image B, it makes sense that a similar-image search for image B would produce image A.  This would create a video that just goes A-B-A-B-A-B-A… To avoid this the artist skipped search results that had already been used in the video, choosing the next-most-similar image beyond the already-seen image.

Tristan Perich – Microtonal Wall

Tristan Perich’s Microtonal Wall is a sound installation comprised of 1,500 speakers, each playing a single microtonal frequency, collectively spanning 4 octaves.  From a distance the piece sounds as if it is presenting white noise, total chaos, like a massive television tuned to a dead channel.  As one gets closer to the artwork one can hear the individual, highly ordered, frequencies presented by each speaker.  The speakers are tuned spatially, so that lower frequencies are on one side of the wall while higher frequencies are on the other.  This creates an interesting pitch-sweep effect as one walks past the wall.

This piece is an effective demonstration a Fourier Series, in which a complex signal is represented by a (potentially infinite) set of simple oscillating functions.

Hello World

Here is a nice patch.