The Exploratorium commissioned Los Angeles-based artist Tim Hawkinson for its adventurous Over the Water series of large-scale artworks for the civic space at Pier 15. It is a tide-activated sound work that re-interprets the bosun's pipe, a whistle used by mariners to give commands in conditions where the human voice cannot carry over the roar of the sea. In creating this monumental experiment with the physics of sound, Hawkinson selected elements of transportation: a shipping container, bus bellows, and a bicycle.

The shipping container, pitched vertically and installed over a hole in the deck of Pier 15, provides the lungs of the system. Tidal waters rise and fall in the container, compressing air and pushing it up into a giant bellows mounted above. The bellows, reclaimed from the pleated section of an articulated Muni bus, provides a steady source of pressurized air, which moves through a hose to the bicycle frame and there blows the bosun’s pipe.

In this video, watch the bicycle-cum-pipe in action. The airflow is controlled by a series of valves, levers, and other mechanisms that emulate a bosun’s hand and mouth motions to produce different sounds in the whistle. Cued by patterns cut into the tread of the bike's rear wheel, the bass bosun's pipe plays 21 different traditional calls, including "Attention," "Carry On," "Swab the Deck" and "Pipe Down.”