Golden Gate Bridge assay 1

"Does the Golden Gate Bridge make sound?" That was the question as we set out to cross the bridge on the brisk morning of December 28, 2008. This was well before we had a web site. It was early morning and a little cold. Not too much traffic yet.

This first walk across the bridge yielded these 24 approximately 1-minute samples in 96 kHz 24-bit .wav format (these have been converted to .mp3 to reduce file sizes). A hand-held Sony PCM-D50 linear PCM recorder was used along with a Fishman V100 piezo ceramic violin pickup and a modified viola bridge. The bridge had a rubber bumper added where the strings normally go, allowing the feet to be pressed manually against the target; the idea was, if the bridge made sound, we’d buy a better mic. We didn’t know how close we could get to the cables or how large they were. The audio is sometimes scratchy as the feet of the viola bridge slip and click against the cables and other metal. Occasional bits of passing conversation appear, along with the constant strumming of the whole structure by vehicular traffic.

[edit] Sights and sounds

December 28, 2008

Golden Gate vid alt.jpg GOldeN Gate on YouTube
We began documenting our walks on video, which was posted to YouTube as a playlist due to length restrictions.

Golden Gate vid alt.jpg GOldeN Gate on Vimeo
The first bridge assay is now also viewable without interruptions on Vimeo.

Audio files are available for re-use and mixing on our Sounds pages. Each text link below points to the download page for the file. If you do re-use the work, please post a trackback to your new composition and announce what you've done.

The walk starts on the east walkway leading up towards the cement pylons at the south end. The traffic noise is especially loud if the pavement is wet.

The first interesting metal appeared to be the various safety handrails. There are multiple short strands of steel on the traffic side. The outer handrail, though, is a thicker cable that follows the main "catenary" curve to allow safety lines to be fastened during maintenance activities.

The various suspender cables appear as clusters of four—actually, the ends of two "loops" over the main cable. Suspenders are longest near the towers.

The towers have a thick sheet steel skin riveted to an internal bracing structure.

Once past the tower, the suspenders become shorter towards the center of the span.

Suspenders are quite short at the center, and the structure—the way the cables arc over the saddles on the main cable, various bolts and stiffeners—can be appreciated. The sound here is quite different from that at the ends of the bridge or near the towers.

By mid-day, the south approach has more traffic but less moisture. Compare this to the first sample.

All audio files on this page Cc by sa 80x15.png 2008 D A Ayer.