Ask the ocean

AI & SOCIETY, 2012

Geoscience Communication

Geophysical Journal International, 2008

The recent discovery that the seismic normal modes of the Earth are excited to a nearly constant level during seismically quiet days (‘the hum of the Earth’) has lead to much speculation as to what drives the observed background in the absence of large earthquakes. Other authors have shown that the hum cannot be explained by the many small earthquakes occurring each day and have also precluded excitation by ‘slow’ earthquakes as the source. The non-linear interaction of low frequency ocean waves (infragravity waves) generates high phase velocity components that excite the seismic normal modes of the Earth. I show the forcing of the normal modes of the Earth by infragravity waves interacting over the continental shelves and over the deep ocean basins is sufficient to explain the background seismic acceleration spectrum observed during seismically quiet days. Atmospheric turbulence is shown to be a negligible source of the Earth's hum. Observations suggesting enhanced spectral levels for two seismic modes that couple strongly with atmospheric modes (0S27 and 0S39) have been cited as evidence that the source of the hum lies in the atmosphere. However, the wave interaction mechanism also couples energy into infrasound and thus may explain these observations. A calculation of the coupling between ocean waves and normal modes expected from ocean waves interacting over the shelves reproduces the vertical acceleration spectrum observed at quiet seismic sites from 2 to 40 mHz including the small ‘hump’ between 5 and 15 mHz and the observed rise at higher frequencies. The model diverges above 40 mHz because the ‘single frequency’ microseism peak is generated by a different mechanism. The shape of the hum spectrum is controlled primarily by the elastic properties of the Earth with the attenuation structure controlling mode amplitudes. A second calculation shows the excitation of Earth's normal modes by infragravity waves interacting over the deep ocean basins can also explain the observed spectrum of the Earth's hum. Infragravity waves are less energetic and the forcing mechanism weaker over deep water, but the integrative effect of forcing over a large area offsets the weaker forcing per unit area. It is likely that both pelagic and shelf ocean wave sources contribute significantly to the forcing of the Earth's hum and both coastal and pelagic source regions have been identified using seismic techniques. Infragravity wave spectra in deep water over the Pacific basin vary little, thus explaining the small variation in the hum that is observed. However, time varying source regions are also observed in the hum, and may be best explained by intense near shore sources. The great similarity between the spectra predicted from continental shelf forcing and from forcing over the deep ocean basins precludes discriminating between coastal and pelagic sources based on the shape of the spectrum. A more complete knowledge of the climatology of infragravity waves coupled with better seismic observations are needed to resolve this question.

Re:Live Media Art histories 2009 Refereed Conference Proceedings (pp. 73-77), The University of Melbourne., 2009

The use of scientific data to create artworks has always played an important part in the arts, and music has been no exception. The impact of developments such as electricity, the phonograph, the cassetterecorder and the now ubiquitous computer on the aural arts is well documented. This paper looks at a different influence however; the use of scientific data as a source for musical artworks, in particular the use of seismic and other low frequency data logged in various formats. As sound art offers different ways to experience aural media, this paper looks at some artists who have experimented with methodologies to create works using meteorological, geological and hydrological data.

Organised Sound, 2015

When Douglas Kahn’s first book, Noise, Water, Meat: A History of Sound in the Arts, was published it entered a very different intellectual landscape to the one we inhabit today. In the late nineties, there was no ‘sound studies’ to speak of. Outside of the music disciplines, the cultural study of sound was scattered across various outposts in communications studies and media theory, art history, literature, urban planning and design, philosophy and more. During this time, it was customary for a monograph on sound to begin with some form of treatise against occularcentricism: the cultural and scholarly bias for objecthood, vision, the image, and concepts of ‘the gaze’ as objects of study. An inherited notion of sound as the ‘forgotten’ object in our cultural environment, and hearing the forgotten sense, seemed to fasten itself to sound, bestowing upon it the status of the perennial underdog - the ‘always emerging, never emerged’ (2005: 249). But the recent boom in scholarly attention to sound means that it can no longer complain of (nor exploit) its own neglect. Sound studies is now a thriving interdisciplinary field, as witnessed by the yearly onslaught of new monographs and anthologies, the slew of high profile international conferences, the new journals and special editions in established journals, and the initiation of large interdisciplinary research centres devoted to the study of sound and sonic cultures. An outcome of sound studies’ ongoing disciplinisation is the possibly reluctant emergence of a ‘canon’ of significant works, which Noise, Water, Meat is now firmly installed within. Ostensibly a history of sound in the arts, the book has come to assume a position alongside the likes of Jonathan Sterne’s The Audible Past and Emily Thompson’s The Soundscape of Modernity as a field-defining history of modern aurality; a counter-narrative to textual and image-based histories of modernity.

2012

The recently reinvigorated field of infrasonics is poised to provide insight into atmospheric structure and the physics of large atmospheric phenomena, just as seismology has shed considerable light on the workings and structure of Earth's solid interior. Although a natural tool to monitor the atmosphere and shallow Earth for nuclear explosions, it is becoming increasingly apparent that infrasound also provides another means to monitor a suite of natural hazards.

Earth and Planetary Science Letters, 2014

2020

The earth forms a gigantic sound theatre. The sound arena, as we may also call it, has been formed in a number of phases. They include the following: the phase of the formation of the natural sound arena (geophony), the formation of the bio sound arena (biophony/zoophony), the phase of the formation of the human sound arena (anthropophony), the phase of the formation of machine-produced sound arena (technophony). All of them are merged into the Earth’s soundscape. In ecological terms, technophony should be kept at a minimum if the Earth’s overall wellbeing is to be considered seriously.

Global Advances in Health and Medicine, 2012