Design students from London's Royal College of Art have created a mysterious floating spherical object that drifts through public spaces recording conversations and plays them back when there's nobody around (+ movie).

Designers Francessco Tacchini, Julinka Ebhardt and Will Yates-Johnson created the Space Replay installation to emit echoes of human presence in public spaces.

"We aimed to draw people's attention to their acoustic surroundings and the temporary way in which we pass through public spaces," explained the designers. "Creating a device that records the noises we make raises sinister questions about the ever-present surveillance in our urban environment."

The sphere contains a speaker and a battery-powered sensory device hacked by the designers to record and playback audio.

The components are encased within a vacuum-formed plastic core and placed inside a latex balloon.

The designers created the cone-shaped plastic centre to improve the sound quality resonating from the speaker, whilst protecting the surrounding latex outer-skin from sharp edges.

A measured amount of helium was added to the balloon, enabling it to reach its buoyancy point and hover.

The balloon travels through spaces according to the natural flow of air in the surrounding environment, which is altered as people move through each space.

"The sphere responds sonically to people and its surroundings," said the designers. "By recording and replaying the ambient sounds it picks up, Space Replay produces an echo of human activity."

Here's a project description from the designers:

Space Replay

The project is a collaboration in-between two departments at the Royal College of Art. It was realised by Julinka Ebhardt, Will Yates-Johnson from Design Products and Francesco Tacchini from Information Experience Design.

Space Replay mediates between people, technology and places by recording and replaying the ambient sounds it picks up, producing a delayed echo of human activity. It takes the form of a floating spherical object that explores and manipulates transitional public spaces with particular acoustic properties.

From a technical perspective the sphere contains a battery-powered Arduino Uno, a Wave Shield hacked to record sound and a small speaker. The components were inserted into a custom designed lightweight polypropylene "sound cone" — in order to enhance the sound coming from the speaker and protect the balloon from the wires and PCB edges. The balloon was filled with enough helium to be able to lift everything and float, reaching its buoyancy point. The final prototype weighs 120 grams, comprising electronics, packaging and balloon.