Tide Spectra and Tide Sounds

The pattern of tides at any particular port depends on the relative strength of the various constituents. For six representative ports these bar-graphs give the spectrum, showing the contribution of the eight most important constituents.

In the first two the semi-diurnal (blue) constituents dominate. This spectrum produces tides like those for Bridgeport and Bombay. The sound files are "sonifications" of the time and height of the extrema of the tide curve: high and low tides.

In the next three the diurnal (red) constituents are stronger than the semi-diurnal. In each of these ports this leads to an alternation between an two-tide-a-day pattern and one-tide-a day. The green bar represents M4, a quarter-diurnal tide.

The musical patterns were generated by Stephanie Mason at the Geometry Center, University of Minnesota. Stephanie wrote C-code to generate 10,000 hours of predicted tides for these ports (using tidal constants provided by the NOS; our thanks to Tom Kendricks) and programmed a NeXT-MIDI interface to generate the corresponding soundtracks, interpreting the times and heights of high and low tides for each port as the notes of a musical score. Each second of the score encompasses about 24 hours of the tidal record.

Here are some additional tidesounds produced by Stephanie Mason. The numbers in the table give the heights (in feet) of the most important constituents:

	M2	S2	N2	K1	M4	O1	P1	K2
Otomari, Sakhalin Island	0.656	0.312	0.102	0.719		0.715	0.240	0.095
Cordova, Alaska	4.712	1.599	0.957	1.615	0.173	1.001	0.530	0.463
Washington, D.C.	1.307	0.185	0.249	0.154	0.137	0.108	0.051	0.066
Ras at Tannura, Persian Gulf, Saudi Arabia	1.951	0.651	0.416	0.471	0.073	0.380	0.142	0.231
Miami Harbor Entrance, Florida	1.199	0.240	0.274	0.134		0.109	0.041	0.063
Daytona Beach, Florida	1.915	0.342	0.472	0.322		0.246	0.106	0.072

Tidal data courtesy of NOAA.

June 17, 2011
Converted to mp3, May 20, 2015

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