Super-sonic listening

One of the circuits I made in my Basic Analog Circuit class was a electret microphone amp that  can have almost infinite gain. It samples itself and regulates the gain based on the input. In a quieter environment the gain can become so high that it is possible to hear things that normally the human ear cannot hear.

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The ITP floor is quite noisy so nothing too out of the ordinary presents itself, though some sounds are much louder than normal: 

The wooden mirror sound really interesting, though the general noise from the busy floor interferes: 

I then went into the stairwell to try to find a quieter place. I had just eaten some almonds and was moving my tongue around in my mouth, and I could hear all the sounds in my mouth! Here is a recording, the mic was no where near my mouth, it sounds sort of crazy: 

I then went into the back stairwell, where there are some interesting oscillations going on: 

 

Resonant Frequencies

Every object has one or more frequencies it vibrates at. Wikipedia says:

“In physics, resonance is the tendency of a system to oscillate with greater amplitude at some frequencies than at others. Frequencies at which the response amplitude is a relative maximum are known as the system’s resonant frequencies, or resonance frequencies. At these frequencies, even small periodic driving forces can produce large amplitude oscillations, because the system stores vibrational energy.”

A tuning fork is a small example of this. You strike it and it starts vibrating at a certain pitch, it’s resonant frequency. In the human body we have several resonant frequencies. The eyes resonate at about 20hz, the digestive track at about 7hz, the brain can go down to 1hz. If a 7hz frequency is played loud and long enough it can kill you. This is because as the digestive system starts oscillating at it’s resonant frequency, and that frequency continues to supply more energy,  the oscillation becomes and stronger and stronger until the thing that is vibrating breaks and falls apart. This can happen with buildings and other large structures too. Its called a resonance disaster. A famous example of this is the Tacoma Bridge which resonated itself to death in 1940:

I wanted to see if I could find the resonant frequency of an object. I didn’t want to destroy anything, but just figure out how to do it. Maybe I code use the information creatively? I started with this PVC pipe:

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After researching online methods to do this, I tried passing a sine wave through speakers into the pipe. I had a microphone on the other side attached to an oscilloscope, the theory being that if the pipe resonates at a certain frequency the waveform on the oscilloscope should jump.

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This didn’t work out so well so I went old school and decided to use my body as the instrument… i.e.,  I put my hand on the tube and felt it, and my ear to the end of it and listened to it.

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I could definitely hear and feel the resonance get stronger at certain places. These places turned out to be the overtone series with a fundamental note of B. The overtone series (harmonic series) is a base of multiples over a fundamental pitch. The sound we hear from a piano playing one note is actually that note with its overtone series on top of it, each upper partial being weaker and weaker, so that we usually just hear the fundamental.

I made a recording with my phone of what ambient sound coming through the tube sounds like: 

Hear that pitch everything is tinted with? That’s a B.

 

Blind Sound Walk II

Later on the same day as the previous blind walk we went to La Monte Young and Marian Zazeela’s Dream House on Church Street.

This is a permanent installation where La Monte Young has set up several oscillator’s at different pitches as drones that never change. The pitches are such that they interplay with each other, creating ripples and oscillations between themselves. The idea of the installation is that the longer you are there with the sound your perception of it will change, and it will sound different.

Here’s what it sounds like: 

At first we sat down on the wall and listened. Sure enough, worlds began to unfold as we listened longer and longer. I could hear bass tones, and upper tones, and rumbles between tones that were close together. It was fun exploring.

At some point though, I noticed that if I moved my head a little I could hear some different pitches that I didn’t hear before. After a while of playing with this I realized that the room was enhancing or attenuating certain wavelengths at different places in the room, making the sound changed as you moved your ears in space. In acoustics each room has different places of resonance where some frequencies are deadened or intensified. I got up and walked around totally excited that moving around in the space you could play the music, and the music itself was never actually changing!

I then grabbed the blindfold from before and put it on Kiori and moved her around. After a while she wanted to walk around on her own, blinded, and explore the sounds of the room and the installation, so I just followed and kept her from running into things. We then switched and I walked around blind. I could of stayed there for hours exploring that sound world…

Blind Sound Walk I

Marshall McLuhan, in his “Visual and Acoustic Space,” tells the story of Jacques Lusseyran who was accidentally blinded in elementary school. Lussseyran, talking about being blinded, says:

“Sounds had the same individuality of light. They were neither inside nor outside, but were passing through me. They gave me my bearings  in space and put me in touch with things. It was not like signals that they functioned but like replies…”

After this quote McLuhan goes on to postulate that in modern society we are much more visual than aural. He says that this was not always the case and that before the collapse of oral traditions sound eclipsed sight, and we lived in a primarily audible universe.

I decided I wanted  to see what it was like to be blind. My wife and I went to South Williamsburg and helped each other do blindfolded walks around that neighborhood:

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At first it was scary, the fear of falling down or getting run over or something else outside of my control happening overshadowed the experience. After a little while of walking though, my brain/body realized Kiori (my wife) wasn’t going to let anything like that happen. Once I could let go of the fear I started to analyze sounds: oh there is a truck, oh someone is walking past me, a car over that-a-way is honking it’s horn. I was also involuntarily putting together a mental image of what I thought the space I was walking through looked like. After a little while longer of walking I let go further and this analyzing of sounds and visual imagining passed away. I found myself in a wash of sound, sound coming from everywhere of all various types. It was such a rich world, and I enjoyed it thoroughly.

After completing our route we switched, Kiori put on the blindfold and I led. This time around for me the sounds had such less precedence. I found myself totally absorbed visually and not even really paying attention to the sounds. It was a completely different world! I realized how visual I really am. The way I imagined the route looking when I was blind was totally different from how it looked in reality as well.

Genetic Algorithm Chord Progression Generator – idea

I’d like to create a plugin for DAW’s and/or an iPhone app that generates chord progressions genetically. This would start with a large database of chord progressions from all types of music that I will accumulate.

Algorithm

  • initial population is a random selection of progressions from the database
  • initial crossover will happen at random from initial population without fitness to generate something for the user to listen to
  • fitness will be two parts: 1. user will listen and rate how the progression sounds. 2. chord progressions adhering more closely to voice leading rules will receive higher fitness
  • mutation will happen to random parts of the population with a markov chain analysis of the entire database

User Interface

  • knobs: 1. evaluating fitness, 2. changing tempo of chord progression (playback), 3. changing rhythm (playback)
  • buttons: 1. evolving to next round (will evolve only once then loop new chord progression), 2. starting over with completely new population, 3. adding current chord progression to database (database evolves too)
  • screen for feedback

Here is a quick initial UI mockup:

chordGeneratorUI