In five years’ time, when Barcelona’s largest urban regeneration project is complete, the Plaça de les Glòries Catalanes will be a leafy oasis in the middle of a new business and leisure district. For now, recent arrivals on the square — including a Jean Nouvel tower, b720 Arquitectos’ mirror-roofed market hall and MBM Arquitectes’ anvil-shaped design museum — must contend with the sight and sound of elevated highways scything through its heart. Appointed to create a permanent installation on a newly landscaped plaza in front of the museum, multi-disciplinary designer David Torrents has made a virtue of this condition, using the noise of the city as an input for a responsive light show, BruumRuum!

Sensors in a canopy that snakes along the northwest edge of the plaza pick up the background buzz of the city: engine hum, clanking trams, the rumble of subway trains below. They are linked, via a PC running Madrix software, to 522 in-ground linear LED fixtures. Ten rows run in pairs along the length of the 35,500-square-foot plaza. For economy, most fixtures align with the joints in the granite paving, though some are laid in diagonal cuts across the square stone slabs, creating a rippling effect. After dusk, shades of red, green and blue light register the intensity of ambient noise.

At the western end of each twin strand, a chest-high aluminum ‘trumpet’ is set into the paving. Sensors in the mouthpiece of each translate visitors’ voices into one of 35 geometric patterns designed by Torrents, which are superimposed across the blocks of colored light. The animated motifs, governed by a script developed by programmer Rebeca S'nchez, are revealed by the absence of light or contrasting colors. Individual fixtures can be partially or fully lit, or display multiple hues along their length.

Users are left to discover for themselves the connection between speech and light. As they learn that holding a note makes the pattern clearer, or that shifting pitch brings new ones into play, they are drawn into experimenting with their own voices, and the plaza fills with joyful roars, whoops and ululations. A man bellows into the mouthpiece and pulses of white light race away down the array of pink lines towards the museum at the far end of the square. A woman shrieks, and strips of solid color briefly fragment into speckles like luminous raindrops. The scene changes again and a child sprints off in pursuit of an elusive shadow shape moving erratically through an azure field.

During the hours of operation, from dusk to midnight, the plaza is rarely crowded, lending an intimate quality to a public spectacle. But if visitors can initially be disconcerted by the combination of light and sound in so large a space, inhibitions are quickly forgotten, says Torrents, “and they just shout, shout, shout.”