Imagine putting on headphones and finding yourself submerged at a chosen point in the ocean, hearing a spatially realistic soundscape. Depending on where you are, you will listen to actual whale song recorded in, or attributed to, that oceanic area, perceptually spatialised so that you can swim closer and around the sounds, turn your head, and experience immersive underwater six-degrees-of-freedom sound.
That is what the XR Sound Map sets out to do. It does not exist yet: I aim to build it over the coming months, as a browser-based application that will render the recordings of the Archive as a navigable acoustic environment. The sound maps that exist today let a visitor click on a location and play a clip. This one will let you move through the sound, in three degrees of freedom by turning, in six by travelling through the scene. What Street View did for the road, this will do for the water: a swim-listen through the ocean.
The positions of whale sounds will come from passive acoustic monitoring, bottom-mounted recorders that register their own position and the time, from which the position of a calling whale can be estimated, and from satellite telemetry, so that archive recordings can be aligned with recorded migration paths. Tagged sources will be rendered relative to the listener’s virtual undersea ears with higher-order Ambisonics, using the JSAmbisonics library developed at the host laboratory.3 A listener will be able to swim with a group of whales, approach or retreat, and, where the archive allows, hear a region change across seasons and years. Layers of geophony, anthropophony and individual species will switch on and off to expose their contrasts.
A clean, minimal interface will visualise whale paths and sound sources while keeping the attention on listening. The application will also teach the acoustic properties of the sea itself, above all the SOFAR channel, the depth at which sound refracts and carries across ocean basins. The calls of blue and fin whales are low enough in frequency to travel in it and have been detected more than a thousand kilometres away;2 whether whales use it to keep contact across oceans, as proposed in 1971,1 is still an open question. It carries human noise just as far. Rendering that principle audibly will turn an abstraction into an embodied experience. The application will run in the browser on computers, mobile devices and VR headsets, with a record function so that listeners can capture and share their own sound dives. The code will be documented and shared openly.