Spiral Echoes Exhibit at City Hall

I was walking out of the Western SOMA Task Force meeting tonight and down the stairs of the grand staircase at City Hall when I heard faint sounds of birds chirping and streetcar bells.  When I looked around I saw a poster for an exhibit called Spiral Echoes that was installed to commemorate the 10th anniversary of the renovation of City Hall.  The link to the Chronicle story is in the blog posting title.  I stood at the bottom of the staircase for awhile and took in all the different sounds.  According to the article "The artist is zapping ultrasonic beams into the rotunda from four transducers placed around the colonnade circling the dome's interior. The sound only speaks when the beam bounces off a wall, a column or a person. Because the transducers are always moving and redirecting the beams, the sounds are always shifting, appearing and vanishing."  As it was 8pm, I was the only one standing there so I don't thing I got the full effect, but still very cool!