Changing Signals is an audio-visual piece created by Dan Tapper, commissioned in August 2013 by GV Art Gallery London for the exhibition Noise and Whispers. The piece explores the hidden sounds of the London Tube and train network. These unheard sounds are produced electromagnetically by trains and equipment and are recorded through custom-built inductor devices. These devices are formed of large coils of wire and convert Very Low Frequency (VLF) electromagnetic radio, a frequency band of the electromagnetic spectrum, into sound and other data. VLF has scientific applications in the fields of radio astronomy and seismography. The recordings expose a sound world that is experienced everyday but never heard by the many passengers of the London train network.
The audio is accompanied by footage of the objects, which generate these sounds set alongside images and film of the scientific apparatus used to record and analyze electromagnetic and VLF data such as oscilloscopes, spectrograms and seismographs.
Changing Signals is comprised of three sections each focusing on a different aspect of the sounds recorded.
The first section looks at the sounds experienced outside the train standing on platforms: hums and drones increasing in intensity as trains approach. The footage is inter-spliced with that of an oscilloscope, a device used to visualize oscillations in electrical voltage. Like standing on a platform, this provides a surface level view to the sonic landscapes of the underground network.
The second section takes place inside the train carriage. The sounds become more intense as the receiver is exposed to greater electromagnetic fields. A number of spectrograms – visual representations of an audio spectrum – are incorporated into the footage, looking further into the interior of the sounds.
The final section takes place outside of the tube network on an over-ground train. Surprisingly this proves to be the noisiest section of the work. To represent this, distortions are introduced into the video. The apparatus footage in this section comes from a cardiogram, an instrument that works with similar principles to a seismograph but measures the human pulse instead of earthquake activity. This is used to represent the London transport network as the lifeblood of London.
Accreditations and thanks:
Oscilloscope Footage – Volker Klocke, oscilloscopemuseum.com
Cardiogram Footage – Wellcome Library, London