Book ov Convolucions (DVD)

con·vo·lu·tion (k?n’v?-l??’sh?n)
n.

1. A form or part that is folded or coiled.
2. One of the convex folds of the surface of the brain.

In mathematics and, in particular, functional analysis, convolution is a mathematical operation on two functions f and g, producing a third function that is typically viewed as a modified version of one of the original functions. Convolution is similar to cross-correlation. It has applications that include statistics, computer vision, image and signal processing, electrical engineering, and differential equations.

In linear acoustics, an echo is the convolution of the original sound with a function representing the various objects that are reflecting it.

In artificial reverberation (digital signal processing, pro audio), convolution is used to map the impulse response of a real room on a digital audio signal. Common ways of generating this impulse include bursting a balloon and firing a starting pistol, though more accurate results can be achieved by recording playback of a sine sweep, which is then ‘deconvolved’.

These short films together form a ‘book of convolutions’, documents and processes that seek to uncover the secrets of familiar spaces. Many of the sounds in this piece are made from site-specific recordings which have been convolved with the captured reverberations of these spaces, ambience convolved with itself, everyday sounds take on the shape of a handrail, a creaking door, other voices. I am standing in a room, similar to the one you are in now..

Equipment used

Various microphones (Sony, Sennheiser), Fostex recorders, Genelec & Tannoy Reveal monitors, Sony PD-150 camcorder, balloons

Sony Soundforge, Acid, Vegas, DVD Architect

Voxengo Pristine Reverb, Deconvolver

Waves IR1

Ableton Live

The concept

There are 3 parts to this project.

1. Capturing impulses from the Atrium and fire escape staircase for use in a convolution reverb
2. A fluxus-inspired performance taking place on different levels of the Atrium
3. A DVD (for installation on an iMac in the Atrium) containing evidence of the above, recordings using convolution, exploring themes of space, cultural ideas about reverberation, and working with photography and video.

Some ideas relating to the concept:

To get to know a familiar space, its inhabitants, routines, quirks, its layers of sound and searching for quiet moments

A territorial pissing

An exploration of acoustic, virtual, public and social space

How two convolved sounds act upon each other has interesting implications.

I was interested in exploring Alvin Lucier’s “I am sitting in a room” and how this experiment can be applied both to sound and to video (Mary Lucier and others), and also how this idea works in practice with a virtual space.

Convolution Recordings

These consisted of the following:

Using bursting balloons, handclaps, foot stamps, shouts, overtone singing, striking metal handrails, squeaking doors, setting up a sine sweep apparatus to generate impulses. These were then used in recording sessions to generate material for inclusion on the dvd.

The sine sweep recordings are deconvolved to produce a bang-like impulse (bursting a balloon is the quick and easy way to excite the response of a space and thus generate a decay that can be applied real time as a reverb effect)

Using a genelec in the stairwell produced a reasonably flat response, though it lacked enough power to excite the space fully.

Tannoy Reveals in the Atrium (L/R and L+R) were significantly less flat in their response and produced impulses lacking low frequency information. An ideal setup would be to use a 2.1 setup with as flat response and high output as possible.

A fully inflated balloon produced a loud enough impulse, though this created problems with distortion and SPL, capturing low frequency information and noise floor from lesser quality microphones than those used for the sine sweeps.

A recording of a Shepard tone (with a slight delay) emanating from my Roland Cube on the stairwell basement level, captured from the top of the stairwell.

An attempt at overtone singing, aided by the stairwell’s natural reverb and converted to an impulse, which became a drone when used in Pristine Reverb.

A recording of a vocal incantation, glorifying the virtues of the stairwell, its reverberation and paying tribute to Alvin Lucier.

Themes of religious significance of ‘holy spaces’, prayers, sacred imagery, I Ching

The fluxus-inspired event featured classmates Luca (harmonica), Shannon (recorder), Moira (agogo) and Ain (singing bowl).

Instructions such as:

make a sharp sound

make a smooth sound

Play music on your phone (sent individually and to all together)

Stamp and Scuff your shoe

Sing and hold a note (when you hear someone sing a note, join in with the same note after a few seconds)

Ignore this instruction

Squeak a balloon

Drop a balloon over the edge and shout “Balloon!”

Were sent by sms individualy and as a group to performers.

An impromptu installation of a wide stereo diffusion in the Atrium using a cd walkman in random play (with silent tracks of varying lengths) and pc speakers.

Material used was from guitar looping and glitch electronica sessions.

DVD Track listing

I ~ O mighty Reverberacion in thee holie Styrwell of Yternitie!
II ~ Sacred chymings ov thee holie handraile
III ~ Thee goode Sheperd tone
IV ~ Songe of thee Creakinge Door
V ~ Balloon of thee depths Ryse ye up!
VI ~ O moderniste archyetktur of always lystening…
VII ~ In wych disciples of Sounde of thee myriad levels get shutte downe for making too much holy noize..
VIII ~ An message from thee grate Easterne Sage
IX ~ Hall of the great illuzions
X ~ Thee drawinge pyn of temptacion
XI ~ Blessed runnings / Thou who Art on hye
XII ~ Book ov Convolucions

Capturing a space's reverb using convolution

In audio signal processing, convolution reverb is a process for digitally simulating the reverberation of a physical or virtual space. It is based on the mathematical convolution operation, and uses a pre-recorded audio sample of the impulse response of the space being modelled. To apply the reverberation effect, the impulse-response recording is first stored in a digital signal-processing system. This is then convolved with the incoming audio signal to be processed.

The primary goal of a convolution reverb is to sample real spaces, in order to simulate the acoustics of the sampled space.

Using a small Genelec monitor I played a sine sweep (12 sec, 30 sec, 60 sec) in the 6-storey stairwell that is used as a fire escape at London College of Communication. The tall enclosed nature of this space combined with hard concrete surfaces and lots of stairs create a unique and spacious reverb. 2 Fostex digital recorders were used, one to play back the sine sweep and one to record in both mono and stereo.

I used a similar setup to record the Atrium at LCC, this time using a pair of Tannoy Reveals and recording only in stereo. This type of recording really requires a high powered full-range monitor to properly excite the space at every frequency. At this level bursting a balloon to create the instant impulse (a sine sweep is deconvolved by comparing it to a dry sweep of the same length) is just as effective, though the Genelec produced better results in the larger stairwell space.

I also recorded several impulses for experimental convolution: striking the metal handrail, a handclap, stomping feet, various shouts and some overtone singing.

These impulses were then loaded into Voxengo Pristine Reverb for signal processing of other sounds.

You can download the pack of LCC stairwell impulses here, and Atrium impulses here

Electromagnetnic Microphone

This is a journey.. into sound… Electromagnetic sound!

These mics are sold as ‘telephone pick-up coil’ for about £5 in Maplin. It’s a small pick-up coil in black plastic moulding with rubber suction pad to attach to a telephone, designed to pick up conversations for recording. Kind of like old-school spy equipment..

Anything electronic or electrical will generate a magnetic field, and this baby will pick up that signal..


..and it goes a little something like this:

1. Library card reader
2. Lift
3. G4 Mac
4. iMac
5. Mobile phone
6. Photocopier
7. PC Laptop
8. TV
9. Payphone

Go get Adobe Flash Player!

Etta Ermini Dance Theatre ~ Fixed Wheel

I was commissioned to compose music and create sound design for a piece of physical dance theatre by Etta Ermini.

After initial discussions about the concept I made the decision to use only sounds recorded from bicycle parts. The chainwheel, forks, frames, wheels, brake levers and spokes became percussion, bells, gongs and were struck or bowed to create a library of samples and loops for placing into Sony Acid. You can listen to the individual cues here

Fixed Wheel is a 30 minute Physical Theatre piece for two male performers and a bicycle. It depicts the joys and pitfalls of the life and love of a geeky bike freak and his alter ego. The movement material is explosive and, at times, quirky. Dialogues are witty and acerbic. The acrobatic use of the prop, a bright blue BMX bicycle, heightens the tense atmosphere. This playful look at loss and longing aims to connect to the personal experiences of the audience. Be safe, wear a helmet!

Reviews: ‘Fixed Wheel’ is an exhilarating piece, with a wonderful mix of Ballet, Boyz and Bikes! Fast-paced, playful and touching, it proved a decided crowd-pleaser to dance-fans, theatre-goers and new audiences alike. Recommended!
Jasmine Cullingford, The Blue Elephant Theatre
Length: 30 minutes
Choreography: Etta Ermini
Performers: Ian Garside, Luis Frontana
Sound Design: Yan White

Performances:

•   Fixed Wheel 2009: Sogni VZW Festival, Ghent, Belguim in May
•   Fixed Wheel 2008: Big Dance, Scoop, London (7th of  July)
•   Fixed Wheel 2008: Cloud Dance Festival, London (6th of July)
•   Fixed Wheel 2008: Atelier Festival, Baia Mare, Romania (16th of June)
•   Fixed Wheel 2008: The Blue Elephant Theatre in April
•   Fixed Wheel 2008: as part of Artscene festival in Ghent, Belgium in April