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