Surface Resonance…

Phase 1.2: Research Detail - articulation of building materials

Phase 1 findings on articulation of building materials came mainly through the initial field recordings of vibrations from nightclubs, and the controlled testing to excite a building structure using a large PA setup.

 

Exploring materials

Nightclub recordings

TMy first approach to capturing bass-induced vibration was to take recordings outside nightclubs.

Background research included seeking advice from online music communities and promoters about venues with bass vibrations. After surveying sound from eight potential sites, I focused my recordings on two venues with the most obvious vibration characteristics.

At the first venue, Brown Alley, the music was dub/drum and bass. After investigating the bathrooms, stairwells and service areas, I took recordings from the windows and doors of the venue. These were located near to the subwoofers and offered clearly punctuated mid-high frequency vibrations.


Nightclub recording - bass passing through door

At the second venue I used rooftop access to a nightclub with house music and recorded the rattling of the metal sheeting and fixtures.

The recording process helped me better understand the acoustic characteristics of vibration.

When recording sound from a window or door, the timbre would change dramatically depending on where the microphone was placed. The distance from the source made a big difference, as the sound became less ‘aggressive’ or ‘sharp’ with distance.

This recording process also clarified how complex vibration sound is. By using close miking techniques, I could hear the way the whole panel of a window or door vibrated in different ways across its surface. The overall sound was made up from the composite of these vibrations interacting and supporting each other.

This finding cast doubts about how effectively I could ever synthesise vibrations through Max/MSP, especially for more complex objects such as panels. It did however suggest that if I was able to take clean recordings of vibration sound, and process these into very small samples, they may be able to be used in wavetable synthesis.

Setting up and recording vibration with soundsystem setup

The testing of blurred basslines through the large PA (see abstraction of riddim) also involved experiments with how to best record the resultant vibrations in the space. I tried different placement distances, and using stereo pairs vs close single miking. Close miking seemed to offer the best result, as it picked up the higher frequency sounds.

I also deliberately set up vibrations, by placing glasses and cups next to each other. The sound was generally not as interesting as wall/panel vibrations, because the sound source was quite obviously identifiable, and the vibrations didn’t seem to ‘match’ to particular bass notes to the same extent a wall resonance would.

Max/MSP work, for emulating and controlling vibration-like sound

During this time, I also attempted to build a Max/MSP patch to emulate the sound of vibrating materials. The idea was to use generated or recorded low frequency sound, and design sound software to ‘respond’ to such sound when at an appropriate level/frequency – generating a sympathetic vibration sound in response, which could be controlled and spatialisied.

The project included:

  • consultation with a vibration acoustics specialist, Jim Minnague, who explained some of the physics of vibrating surfaces
  • online research and seeking assistance from Max/MSP forums, and acoustics groups
  • trying to develop Max/MSP processes that copied the ‘real-world’ physics of vibration (for example, the modelling processes of Perry Cook)
  • searching for acoustic data of resonating materials, such as their spectral makeup
  • looking at how to generate content based on such real world data, such as additive synthesis from broken down samples of vibration (application Spear)
  • looking into wavetable synthesis as a means of making sounds
  • phase control of short sinusoidal samples

This technical process helped me to understand the physics of vibration. A material will oscillate in sympathy with low frequency sound, until its range of movement is ‘truncated’ by its physical boundaries (for example, a window pane in a loose frame), at which point it abruptly ‘clips’ and generates non-periodic harmonics based on the original activating frequency.

This understanding was the basis for the Max/ MSP programming, and also informed my later approaches to composition, such as thinking about thresholds in level above which vibration or distortion would be activated. I dropped this arduous programming process after some months, as I realised that vibrating material sounds were far too complex for me to emulate, and recordings offered more interesting source material that I might be able to control in a way similar to the Max/MSP intent.

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Reference Material


    Max/MSP patcher examples

  • Resonation patcher
  • Synthesis subpatcher