Controls
- The Hold Time button will keep the piece at the current time period. After you click it, it will become the Resume Time button, which will let the piece continue advancing through time.
- The Animation On/Off checkbox will start and stop the background animation.
Data
This is a data sonification (a presentation of data as sound) of the world's ocean heat content from 1970 to 2025.
The term "ocean heat content" refers to the energy that the oceans have absorbed from the heat that has been applied to it. The data being played in this piece are measurements of the change in heat content in the top 700 meters of the oceans, relative to the ocean heat content in 1955. This change value is referred to as the Ocean energy anomaly in the display.
The data comes from NOAA's NCEI Heat Content Basin Time Series data set.
Units
The energy unit shown in the display is zettajoules. A zettajoule is 1021 joules.
Human annual world energy consumption is approximately 0.5 ZJ. The energy to raise the temperature of Earth's atmosphere 1 °C is approximately 2.2 ZJ.
A zettajoule is about 16 million atomic bombs' worth of energy.
Representation
The greater the ocean heat content in a period of time, the denser the chord that is played. So, if a period of time has lower OHC, the sonification will play a sparser chord. Then, if the next period of time has more OHC, a denser chord will be played. OHC changes and chord density (the number of pitches in a chord) have a linear relationship.
Each time period in the data is three months. However, in this piece, not every datum is played for the same length of time. To accommodate listeners that may not be accustomed to dissonance, denser chords (which correspond to higher OHC) are played for shorter lengths of time. Similarly, as the listener (presumably) gets more accustomed to the piece the amount of time a datum is played is additionally reduced.
The tonality diamond
The pitches in the chords come from the 11-limit tonality diamond. The tonality diamond is a way of extending the just intonation tuning system. Just intonation derives pitches via (relatively) simple frequency ratios. For example, an octave is twice the frequency of the root pitch (as it is in most tuning systems), the fifth is 3/2 the frequency of the root, and the fourth is 4/3.
The tonality diamond can produce more and finer divisions of pitch than just intonation does while maintaining simple ratios. The 11-limit tonality diamond used here has thirty pitches between the root and the octave (inclusive), as opposed to a conventional tuning system's twelve.
In the display, the tonality diamond is pictured to the right of the ocean energy anomaly value (or under it if the window is narrow). If a pitch is being played, it will be drawn in its place in the tonality diamond. It will show its ratio to the root pitch. If you click on the pitch, the frequency and approximate western music pitch name (e.g. 92 Hz, F#) will be shown. When OHC is higher, more of the tonality diamond will be drawn.