30 September 2008

Sonification of tides

To say that this post is relevant to the content of Science, civilization and society is stretching credibility, but it has some entertainment value and is related in some way to the discussion of tides in my blog "The tide predicter of the U.S. Coast and Geodetic Survey" of 25 May. In that post I referred to a web page with an animation of Kelvin's Tide Predicter. The same page has a link to "Tidesounds", where tidal constituents are used to produce "musical scores." You can listen to some examples here: Miami harbour entrance, Daytona Beach, Florida, Cordova, Alaska.

The Tide Predicter page says that "the musical patterns were generated by Stephanie Mason at the University of Minnesota Geometry Center, who wrote C-code to generate predicted tides for these ports, and programmed a NeXT-MIDI interface to generate the corresponding soundtracks." You have to admit that the resulting sounds are more of educational/scientific than musical interest. I asked my son Sebastian, who studies music technology at the University of Adelaide, to produce a bit of sonification of some observational data from one of my field studies. He used data from an oceanographic data buoy that recorded (among other things) wind speed and direction, ocean current and temperature and conductivity at various depths in Thorny Passage near Port Lincoln, South Australia. Here is the result: Southern Ocean sounds.

Seb used the observed wind direction to set the rhythm and the battery voltage to control the loudness; he converted the conductivity at 2.5 m depth into marimba, the temperature at 2.5 m depth into soft organ and the salinity at 2.5 m depth (calculated from temperature and conductivity) into drums. As the water moves in and out through the Passage with the tide its salinity and temperature change slightly, so the up and down of the melody mirrors the tide. The variable speed of the rhythm is produced by the passage of atmospheric fronts that cause sudden changes in wind direction. It does make for more interesting music than just tidal heights from a tide table, don't you think?

You can find Seb's own blog here.

1 comment:

Owain said...

Interesting stuff. the link "Southern ocean sounds" does not work

Would like to hear it

We have been sonifiying tide stuff here in the uk

email o.jones(AT)bathspa.ac.uk if you want to link up