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This booklet is a review of the technical research I’ve made during my process of making and discovering sound. All the contents are written by myself during Semester 1 (Feb-Jun) 2015 as part of Around Sound Upperpool course. Teacher: Sophie Gaur RMIT. Melbourne - Marta Vidal
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space and acoustics
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noise
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acoustic absortion
material structure
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chicken wire
paper and wire
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polypropilene
acrylic felt
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SPACE AND ACOUSTICS When talking about sound in space, considerations change if talking about a big open space or a closed and smaller one. Greeks and romans built theatres many years ago with perfect acoustics and their classic heritage is still used today. Diffusion of sound in big spaces is preponderant due to the tridimensional expansion the waves suffer. In the other hand, reflexion of sound is the main phenomenon in small spaces, not only the sound coming frmo the inside of the space, but also the surrounding sound from the outside.
There is a popular folk myth that says that if one holds a seashell -specifically, most often, a conch shell- to one’s ear, one can hear the sound of the ocean.
SOUNDS CAN BE CLASSIFIED BY OUR SUBJECTIVE RESPONSE TOWARDS THEM. IN THIS FRAME, NOISE IS UNDERSTOOD AS AN UNDESIRED SOUND WHICH INTERFERES IN OUR LIFE, USUALLY AS A RESULT OF A COMPLEX MIX OF SOUNDS. SO EVEN THOUGH THERE IS A SOCIAL COMMON PERCEPTION TOWARDS THE MAJORITY OF NOISES, IT’S OUR OWN SUBJECTIVENESS WHAT DEFINES IF WE LIKE A SOUND OR NOT.
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The resulting noise from all the noises of a concrete space is known as “environmental noise”. Noise can have different intensities and pressures, but it will never get to the absolute zero. Apparently complete silence even affects human nervous system, and it’s totally antinatural. A constant noise in a low frequency is the most dangerous, even though it doesn’t cause direct physical damages, the fact that it can be practically unappreciable can have psychological consequences. There are several kinds of environmental noise such as background noise, aleatory noise, white noise… white noise is considered by many a relaxing background “filling” when wanting to concentrate in a certain activity.
Noise can come from different fonts, some of them near, others far away, it can be produced from the reflection of sounds in surfaces and it can even come from all directions.
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NOISE CAN COME FROM THE STREET, FROM CARS, TRAFFIC, TRAINS, METRO, TRUCKS, BUSES, PLANES AND HELICOPTERS, PUBLIC WORKS, KIDS IN SCHOOLS, MARKETS, CROWDED STREETS… AND IT CAN ALSO COME FROM OUR OWN HOME, FROM PEOPLE, NEIGHBOURS IMPACTS OR FOOTSTEPS, MUSIC PLAYERS, TV, ELECTRICAL APPLIANCES, STRUCTURAL INSTALLATIONS LIKE PLUMBING, ELEVATORS, HEATING OR AIR CONDITIONING, EVEN DOGS BARKING.
The presence of noise in our everyday life is evident and we don’t usually pay attention to it. Due to it’s physiological and psychological effects, noise is an important matter in industrial societies, causing in it’s citizens consequences such as an acceleration in cardiac rhythm, change in the breath, change in arterial pressure, etc. Environmental noise makes us have to raise our voices when having a conversation with someone, as well as pollutes our hearing without us realising. The effect of noise is different in every one of us, our mood and capacity of isolation will influence in our reaction. But it also depends on the kind of noise, a regular and constant noise will be generally accepted.
ACOUSTIC ABSORPTION is the fraction of energy which has not been reflected on a surface or an object
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Acoustic absorption depends on the space and the air in relation to the barriers that limit it. This means the physical barriers that are placed in space influence in the direction of the sound wave, and will repercute in it’s final acoustic result, either maximising or minimising it depending on it’s shape or surface texture.
John Cage was one of the most influent musicians of the 20th Century. He built this anecoic chamber in which he wanted to generate complete silence. He found out there is no complete silence, our body is in the end the last generator of sound.
The chamber of whispers in the NYC hall is one of many in the world, where perfect reverberation takes place. Somebody can whisper a message in one point of the space, if the listener is positioned in the corrrect point oposite him he will listen the message perfectly, even though a long distance separates them.
REVERBERATION When sound reflects successively in all the barriers or walls, reverberation occurs. Reverberations depends on the shape of the space, where in the space does the sound come from and the capacity of absorption of the material the walls are made of.
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POROSITY AND MATERIAL STRUCTURE’S INFLUENCE IN ACOUSTICS Materials with an open cell foam structure are highly absorbent, due to the acoustic wave reflects and gets stuck in the small cavities. When a foam is cut with a wavy surface (anechoic cones) it acts as a sound trap. In contrast, highly polished surfaces reflect orthogonally the waves without keeping any of it, giving place to echoes.
models and trials
CHICKEN WIRE STRUCTURE
By generating 1:1 scaled volumes I started to get the feeling of big shapes in space, their relation to human scale and body. Generating a very basic wire bubble which I hung I started to see which dimensions where comfortable to be inside without loosing the “wraping” effect. Also the use of simple wire was helpful to build more geometrical shapes, putting together several elipses. This first fase was totally naïf and based on intuition to find which kind of shape suited the best for what I was willing to make.
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Chicken wire was an easy and quick first resource to build basic shapes.
PAPER AND WIRE STRUCTURES
It was easy and quick and I could get a better perception of the volumes I was creating and their spatial effect. By wetting butter paper and layering it on the wired structure a whole new cocoon came to life. I generated several of these, they were quick three dimentional sketches with which I could materialise what was drawn in my sketchbook. These prototypes made me want to have an “up going” structure, I was fascinated by the “pipe effect” of the volume going up. I also liked the surface texture, It was relaxing to observe while paying attention to the sound.
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Keeping the wire but wanting to cover it, I decided to keep going with paper maché.
POLYPROPYLENE
Richard Serra’s compositions were a big refferent during this phase. Polypropilene worked easily when inserting the ends, and could be slightly deformedwhen applying temperature. I also tried blowing some sheets with the vacfoaming maschine, getting plastic bubbles with interesting unpredictable shapes but with very thin walls. Some of the models were combined with elastic fabric as an aesthetical experiment.
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Polypropilene turned out to be a good reflectant material easy to bend and generate shapes. Several trials were made in paper and in real scale polypropilene. At first a simple cone was put together, and the sound effect was correct, so then I went on exploring different possibilities. Many of them were beautifull but difficult to formalise.
ACRYLIC FELT
The felt didn’t answer as I expected. It was very thin (1mm) and didn’t hold in the shape I wanted. Moreover, it wasn’t as absorbent as expected. Anyway, I learnt skills such as I could slightly melt the material’s surface and stick it together without the need of glue. I could also generate interesting superficial patterns. It was not sturctural, I would of needed a thicker and better felt. In the end these trials ended up in the conclusion that: 1. I needed a structural skeleton to hold the material and 2. it had to be thicker so I could get a more absorbent effect.
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As an absorbing material I started working with felt. As it was acrylic and it’s composition was 100% polypropilene fibers I also played with temperature, after all the trials with the thick 5mm solid sheets.
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AS A CONCLUSION OF ALL THIS RESEARCH AND PRACTICE I REALISED I COULD GENERATE TWO SHAPES. THE FIRST ONE, MADE OUT OF POLYPROPILENE, WHICH FOCUSED ON REVERBERATION OF SOUND. THE SECOND ONE, MADE OUT OF FOAM, WOULD FOCUS ON ABSORTION OF SOUND. THE TWO OF THEM WOULD BE HELD TOGETHER WITH A STRUCTURAL SKELETON.