]Architectural Acoustics - An Introduction
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Notes from the lectures given at University of East London Department of Architecture
Undergraduate (2nd and 3rd year) Studio B
19 December 2008 by Marcus Beale MA Dip Arch RIBA
[Note on these notes: these are basically speaker’s notes, an aide memoire, I am gradually updating and fleshing out as a proper Course on Acoustics in Two Lectures which will be rolling out across the UK in 2009/10.]
1. Introduction. These lectures set out some principal themes of architectural acoustics. The aim to give a framework from which to explore the audible realm of architecture. We cannot explore the ideas in detail here, rather set out the themes and invite you to do some more research. A fuller discussion is in my forthcoming book Sensuality and Proportion.
The structure of these lectures.
In part one we explore some essential concepts, to do with listening, sound, cities, habitation, the physiology of the human body. This helps us define a broad subject and gives us some conceptual tools.
In part two we deploy these concepts in actual situations, draw some conclusions and identify opportunities for further exploration and research.
Part One - Concepts, Cities, Humans
1.1. I start with a text from Luigi Russolo, and Italian Futurist of the early 20th Century. He is writing about Milan, a prosperous industrial city in the plains of northern Italy:
‘Let us wander through a great modern city with our ears more alert than our eyes, and enjoy distinguishing between the sounds of water, air, or gas in metal pipes, the purring of motors which breathe and pulsate with indisputable animalism, the throbbing of valves, pounding of pistons, screeching of gears, clatter of street cars on their rails, cracking of whips, flapping of awnings and flags. We shall enjoy fabricating the mental orchestrations of the banging of store shutters, the slamming of doors, the hustle and bustle of crowds, the din of railroad stations, foundries, spinning mills, printing presses, electric power stations, and underground railways...’ Luigi Russolo [the Art of Noises 1913]
The point here is that ambient sound, the background sounds of modern life, can be made into ‘mental orchestrations’, the breathing of engines which pulsate with indisputable animalism, the hustle and bustle of crowds: it is all being considered as a whole, it can be enjoyed.
It urges us consider the sound of our buildings, the whole sound of the city, not only concert halls and radio studios, neighbour noise, but everything: to enjoy distinguishing, to learn to hear well and think about what we hear for our whole professional lives.
2. Definition: <Architectural acoustics> means <listening to architecture>.
The etymology is from the Greek: ‘Architecture’ a compound of 'archi'= head or chief, and 'tekton' = builder, which taken together means: one who leads, directs, or is ‘in charge of’: building operations.
This is coupled with: ‘Acoustics’ from 'akoustikon' a listener, one who, by listening, tries to understand the deeper realities of the universe. This rich alive tradition stretches back to Pythagoras and beyond.
[Alternative definition: In 20th century we see ‘architectural acoustics’ defined as the ‘science of sound applied to building’. This is not untrue but oversimplifies: a) It pretends to take the observer out of the equation: a speaker speaks, the sound bounces around the room and the hearer hears - but if you objectify acoustics: make us equivalent to a microphone - how do you put us back? b) It’s based on a crucial omission: that we modify our behaviour in response to sound.]
Enclosure affects behaviour.
The human being is the centre. Start with this and end with this. Human activity creates sound: architecture shapes space, modulates and modifies these sounds: behaviour adjusts in response to architecture.
3. Why listen? To become better designers and better team leaders. Being an architect is not only to design good buildings but to build, to lead teams and guide complex processes with many stages of involvement and consent. A lot of listening involved.
Let’s put listening into context.
4. Synaesthesia.
We experience real life and real space as a synaesthetic totality: all the senses and memory and expectation acting together.
Listening/ sound/hearing is one element of this sensory experience, to be put beside
sight,
touch,
taste and
smell interpreted by
memory: experience and anticipation.
5. Here and now I am. The undivided whole, the oneness: the mystery of being.
To be is to experience reality as a whole. This is unique (particular to you) and connected (part of our collective reality) . The moment we make observations about the world: to say I (unlike you) am this and you or it (unlike me) are that, we are dividing and compartmentalising , splitting reality into fragments. This is fine if we can put the fragmentary knowledge back into a whole.
Life in space is something to be experienced before thinking or talking about it. When discussing sound or sight, touch or smell be aware that what we see and hear are partial aspects or facets of a reality in which we participate - we affect the result of the experiment.
When we consider what a place ‘sounds like’ or what it ‘looks like’ - these are parts of a whole.
6. Listening and hearing. We hear much more that we listen to. Hearing is so acute that we must ‘block out’ or consign to the background the vast majority of what we hear. We can hear almost the heat of air molecules. Listening requires effort on behalf of the listener, and this in turn means that our attention is drawn to events that are worth listening to, and what is not worth listening to - background sound - is ignored. Listening to the world gives us valuable information We listen to what is appropriate and important to us, what we have learned to hear. For example we hear: - things of appropriate wavelength (size) 17 mm to 17 metres, with average about the size from mouth to belly and sound of a man about 6 foot 1.8m long. We don't hear what an elephant hears, or what an ant hears, our centre of attention is different. - Threat sounds, sound of predators, the screech of polystyrene on glass is a trans-cultural nasty sound. - Water sounds - Food sounds - Other humans, and particularly those that we love, and particularly speech song and music. - Music. Valuable sound. Characteristically involving inner structures of harmony and rhythm, related to the resonant rhythms of humans. - Noise. 2 distinct meanings: chaotic sound (e.g. white noise) or more usual colloquial sense, a noise of negative value: (e.g. noisy neighbours) things that worry or annoy us - a value judgement, very dependent on context. For example water sounds in a desert.
7a. Physiology of hearing - ears; two placed either side of the hear to achieve all round hearing - outer ear - pinna to eardrum - location finding - middle inner - eardrum and little bones - collecting vibration and transferring to the - inner ear: round and oval window, labyrinth and cochlea, where sound and balance are sensed - Auditory nerve to the brain - signal processing The threshold of hearing and the threshold of pain. Spatial aspects
7b. Making sound Voice, heartbeat, life rhythms The moving subject movement and dance relation of experienced frequency to human body and movement: allegro andante, torso, limb and finger movements.
8. Space We communicate through drawings and photographs but architecture is not ‘a visual art’. Architecture is about space, the enclosed body of air, shape, material, enclosure. Not only ‘what it looks like’ but what it’s like to live in: fully three dimensional and experienced through time. Time and space. Unlike sculpture, architectural spaces must work for human habitation, they are filled with human activity. They are real lively, disputed, socially, culturally, politically charged. - Solid and void: The air he gaps between the built structure are the parts we inhabit: the value resides in the habitable space. - Enclosure. It is about enclosing habitable space, enclosing humans and human activity. Cupped hands. Making of a wall. Prevents movement.
9. Air : space is not empty. It’s full of air. Just because it’s invisible doesn’t mean it does not exist We live at the bottom of an ocean of air, under pressure. We can feel its weight. At sea level m3 of air has a mass of about 1 Kg. A m3 of water has a mass of about 1 tonne = 10 times more dense in each of three dimensions = 1,000 times more mass. Humans are the same density and salinity as sea water. But air and water are at the same pressure, where water and air meet. And the air (like water) carries information: sound (and smell). Because air is a fluid medium, when compressed it reacts and expands.
10. Sound: Sound is an (audible) vibration of a fluid medium Sound informs - gives form to - of the air Sound : displacement, rarefaction and compression of the air, travelling in waves, as the molecules nudge their neighbours. Waves transmits energy over space. No net movement of matter. Net movement of energy and form/shape.
11. Oscillation and vibration - pendulum vibration: complex of oscillations all taken together. Steel
12. Measuring, describing and quantifying sound: in historical order Wavelength Pythagoras, harmony tubes and strings. Speed of sound: Newton and canon: see the flash before hearing the report Frequency clocks and tuning forks cycles per second or Hertz Amplitude phonometers and electronic measurement pressure loudness decibels a logarithmic scale comparing one thing to another. 10 dB = twice the pressure. 20 = 4 times 30 = 8 times and so on. Compare to the threshold of audibility = 0 dB Conservation of energy Reverberation absorption Resonance a mechanical (or biological) system which favours a particular frequency /wavelength and so will vibrate in this manner
20. Musical instruments. Tubes strings percussion. Bells, horns pipes and lyres. Drums and claves
21. The voice - more like a French horn than a lyre - a continuous body of air lungs pharynx larynx mouth cavities, sinuses soft and hard tissue spectrum of sound individuality of speaker
22. Reverberation - reflecting sound - stone sounds acoustic ‘mirrors’ - absorption - openings
23. The continuity of space and soundscape.
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Part Two Applied acoustics:
30. A method. Consider: - the sound of an activity - the way the built enclosure adjusts/modulates that sound - the way the sound changes the activity
31. City sounds soundscape sounds that are not sounding at present Actual sound and potential sound Aristotle.
32. Sound sources elements living things machinery alarm sounds catalogues of sound
33. Localised environments Theatre dining hall kitchen sleep duvet
34. Room acoustics performer speaker here wall here or here ceiling here or here breaking up the sound absorbing the sound letting it escape Convex and concave surfaces ceilings apses focus first reflections late reflections
35. The cocktail party effect - people can’t hear each other and talk louder and louder to hear each other which makes background sound even louder. So they talk louder - the ability to separate out our friends voice from the background.
36. Affecting acoustic behaviour A notice saying ‘silence’ Colours and acoustics Jean Nouvel theatre concert hall dark blue bad acoustics grey walls good acoustics understanding the sound you hear
37. Introducing sounds into the building - mechanical systems - bells - water - hinges - floor finishes and footfall: gravel boards carpet rubber stone.
38. Making sound - promoting sound - appropriate to context making a building appropriate to context a parallel in townscape: - shouting iconic - or storytelling, stitching together
39. Noise control Physiological effects of noise. Aircraft and traffic noise. - Impact sound - Airborne sound Stuff that stops sound: mass, isolation. Fields of baffles. Active acoustics (cars and Bose headphones)
40. Soundscape - The one sound - private acoustics (walkman) - civic acoustics - parliament. City a collective organism. Air and water. feng shui ____
Further resources can be found at www.philophony.com ____
About the speaker. Marcus Beale is practitioner of architecture and music. He is director of Marcus Beale Architects . Before becoming a professional architect he was a composer of ballets and professional violinist, performing with the Penguin Cafe Orchestra, with whom he toured in Japan USA an Europe from 1981-1985. He is one of few architects to have played the BBC Whistle Test and to have had his music performed on BBC Radio 3. Further information at www.marcus-beale.com