'Fremor' is a thought-provoking art installation by Marc Vilanova that brings to light the inaudible underground vibrations generated by urban infrastructure. With sensitive geophones capturing these low-frequency sounds from subways, road tunnels, and energy plants, Vilanova translates them into visible mechanical movements. Placed on an elevated walkway at the Teatre Nacional de Catalunya, illuminated tubes move in sync with the captured sound patterns, creating a dynamic visual representation of the city's acoustic pollution. This installation challenges viewers to reflect on the often-overlooked sonic environments that coexist with urban life, blending art, science, and technology to foster active listening and awareness.