That Moment When You Earthquake-Proof a Bridge and It Becomes a Giant Aeolian Harp

I first learned about the Golden Gate Bridge's eerie hum from an early June blog post by Marc Weidenbaum, who included video in his post recording the sound from his backyard.  I was immediately fascinated by its shimmering drone and sought recordings of and background on it across the Internet.  Apparently, the noise was an unintended (but anticipated) consequence of wind blowing through the newly renovated walkway/bike path railings, done as part of an ongoing earthquake-proofing of the landmark prompted by the 1989 Loma Prieta tremblor.

However it got there, I loved it.  Indeed, I'm fascinated by the sounds that bridges make (and, for that matter, just by bridges in general), although my attempts to record and make use of/music with those sounds have mostly not gone very well so far (but watch this space).  In any case, I saved audio of the Golden Gate wherever I could find it and eventually began to analyze it with the intent of creating something musical from it.  This is the result:



If you listen to the recordings linked above, you'll probably quickly discern that this is not a recording of the Golden Gate, rather, it's the result of my deconstruction and reconstruction of its pitches, timbres, rhythms, etc. using digital music resources.  My aim was to recreate the song of the bridge closely, but not exactly, taking some small liberties to make it a little more musical; it doesn't need much, to my ears, being already almost the definition of ambient music.

Surprisingly, this was not terribly complicated.  My ear training being very rusty, I guessed (incorrectly) that the frequencies had some simple overtone relationship and, therefore, (correctly) started with simple sine waves, thinking additive synthesis would be a useful starting point.  It turned out that the pitches are oddly near to standard scale pitches:  G3, A3 (A440-ish), B3, A4, C5, and D5.  Although I didn't dig very deeply, I found no evidence that the bridge rail designers did this purposely, so I found it astonishing that the notes were so consistently diatonic -- right off the white keys of the piano. 

After that, most of the work was setting up randomized LFOs to create the shimmeriness of the pitches' relationships, then adding a relatively high-frequency (132ms), high feedback (86%), low saturation (35%) delay and finally a little bit of reverb (Valhalla VintageVerb tuned to huge halls but with the tail dialed way back) to knit the thing together and give it the sense of scale and distance you hear from the bridge.

The work is intended as an ambient piece, to be either listened to directly or left as atmospheric sound.  I found myself drawn to expressly meditative mindsets as I felt through the shape and direction I wanted, so it could fit in that context as well.  Of course, to the extent that I simply mimicked an existing sound, I can take only very limited credit for creativity; however, as a self-expression, it resonates (sic) deeply.

I'm as pleased with this as maybe anything I've done.  It captures/recreates a sound I am endlessly in love with:  a held tone or drone with overtones (or, as in this case, scale steps) that unpredictably jump in or fade out, creating an aural sensation equivalent to watching the light of the morning sun sparkle over rippling water.  I've struggled to produce that kind of sound acoustically (although I'm learning -- again, watch this space) as well as electronically; combine that with what I've learned about the structure of such sounds and this outcome feels especially satisfying.