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SONIFICATION SHOWCASE
A set of quick look examples of our sonifications!
Gravitational Waves
Gravitational Waves
Here we present a Virtual Reality experience, with a sonification of gravitational wave events, from the third LIGO/Virgo observation run. You can hear the events at their approximate location in the sky. The 1 minute video covers the period April 2019 to March 2020. Data from: https://gwosc.org/O3/O3a/ and https://gwosc.org/O3/O3b/
Stars appearing in the night sky
Stars appearing in the night sky
The audience ‘listen’ to stars that appear around them at the European Southern Observatory’s Very Large Telescope (VLT). The data we used are presented in the diagram below, which are the magnitudes, colours and coordinates of stars as viewed from the VLT on the 13th September 2019. We only considered stars with V-band magnitudes <6, to roughly correspond to the limit of the human eye.
Each star is represented by a single note on a glockenspiel from one of five pitches: D flat 3, G flat 3, A flat 3, E flat 4 or F 4, with the choice of note based on the star’s colour. The reddest stars are assigned the lowest notes and the bluest stars the highest notes. During the sequence each star is heard in an order based on its magnitude, with the brightest stars sounding first and the faintest sounding last. This represents how brighter stars appear first to the human eye after sunset.
The stars’ positions were used to determine in which speaker(s) they should be heard. For example, stars directly in front of the ‘observer’ sound in the front speakers for the surround sound version, or equally in the left and right ear for the stereo version.
Diagram demonstrating our sonification of the ‘stars appearing’. Panel a) shows the mapping of V-band magnitude (top axis) and B-V colour (left axis) to triggering time in the audio sequence (bottom axis) and musical note (right axis), respectively. The aligned Panel b) shows the waveform produced for a stereo setup, and the triggering times of the 10 brightest stars (dotted lines). The right panel shows the stellar sky chart, with point size and colour indicating brightness and B-V colour, respectively. In our sonification the observer faces south, with the left and right audio channels corresponding to the east and west cardinal directions, respectively.
Virtual Reality Version
Virtual Reality Version
Our STRAUSS code can also be used to create immersive, full surround sound experience for application in Virtual Reality (i.e., using ambisonics). As an example of this, you can see below the Stars Appearing excerpt from Tour of the Solar System (described above), re-formated for Virtual Reality. In this YouTube video, you can explore the hemisphere sky by using the arrows in the top left. You should notice that the sounds of the stars appearing can be heard in the correct location as they appear (headphones are highly recommended!). If you have a Virtual Reality headset, you can experience this directly through YouTubeVR.
Black Hole Accretion
Black Hole Accretion
Here we add sonification to an existing animation of a black hole system to demonstrate how the visible light and x-rays emitted from the system vary over time.
When listening with stereo, optical data can be heard to your left and x-ray data can be heard to your right.
X-ray data is sonified with a white noise base sound with a frequency low pass filter, the data is used to control the cut-off frequency. The effect is that when X-ray emission is stronger, more high frequencies are heard in the sound. Using white noise gives a 'windy' sound. X-ray sounds are heard to your right.
Optical data is sonified using the same low pass filter method, but with a synthesized musical chord as a base. There are five different optical bands, each of which are sonified using a different note to form a five note chord. The optical sounds are brighter when there is stronger optical emission. These sounds are heard to your left.
The original animation is an artist's impression of the black hole system MAXI J1820+070, based on observations during a rapid accretion episode in March 2018. X-ray radiation was observed by the NICER instrument on the ISS and is shown by purple flashes in the animation. The other colours show the visible light observed by HiPERCAM in La Palma. The video is approximately 1/10th of true speed.
The actual X-ray and visible light time-series data captured (which were used to make the sonifications) appears in graphs about halfway through.
We've provided a more in-depth technical description of how this sonification was put together on our Sonification of a Growing Black Hole page.
Rotating Earth
Rotating Earth
We wanted to sonify sunlight bouncing off the spinning Earth through changing timbre as the Sun passes over water (a “brighter” sound) or land (a “darker” sound). For this, we used data of the covering fraction of water as a function of longitude. To create the sonification, we started with a sustained musical chord, using notes G flat 3, D flat 4, E 4 and B 4. Each note was created from a set of three sawtooth oscillators combined at frequencies on, 2% above and 2% below the target pitch. These choices provide a harmonically rich sound, which is then manipulated by filtering out frequencies (i.e. subtractive synthesis) based on the water covering fraction data.
The longitude and water covering fraction (see figure below) were mapped directly to the time in the sequence and the filtering cut-off frequency of the chord, respectively (bottom and right axes). The cut-off frequency, above which frequencies are attenuated, was calculated from the water covering fraction using a logarithmic scale. A low-pass Butterworth filter (Butterworth, 1930) with a 24dB roll-off was used.
The conversion of water fraction to frequency cut-off can be seen by comparing the left and right y-axes of the main panel in the figure. We note the more jagged, harmonically rich waveform representing a longitude over the pacific ocean (panel c) relative to the smoother waveform representing a longitude over Europe and Africa (panel d). The filtering mainly changes the timbre of the sound but a secondary effect on volume is achieved in that the land-dominated regions sound the quietest (see waveform along the bottom of the main panel).
Diagram demonstrating our data sonification of the Earth’s rotation. Panel a) shows water covering fraction (left axis) versus longitude (top axis) over two Earth rotations with a world map projection as a grey underlay. These values are used to calculate the low-pass filter cutoff frequency for the sonification (right axis). Panel b) shows the waveform of the sonification as a function of time. Panels c) and d) demonstrate the effect of the filter on the waveform by zooming into 20 milli-second windows around longitudes where the water covering fraction is approximately highest and lowest, respectively (indicated by vertical lines of corresponding colour in Panel a).
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