Seeing with the Ears

Bats hear and communicate at frequencies beyond our auditory perception. In flight, they emit cries in the ultrasonic range and orient themselves based on the echo they pick up with their funnel-shaped ears. Hannes Hoelzl, sound artist and lecturer for Generative Arts/Computational Arts at the University of the Arts in the Brain City Berlin, has developed the SomBat, an instrument that trains people to orientate themselves in space by their hearing.

Puiiii, puiii, puii. Tock, tock, tock, tock. TOCK!“ Staccato sounds shoot out of the funnel-shaped megaphone of the “SomBat”. Sometimes louder, sometimes quieter, sometimes lower, sometimes higher. They move through the stone inner courtyard, are angularly deflected by window facets and finally reverberate off walls as an echo. If you listen to the sounds for a while, a spatial sound image is created in your head. What you otherwise primarily see with your eyes, you suddenly “recognise” with your ears. The experiment works best with your eyes closed: Walls, trees, stones, bushes, even passing cars leave 3D sound tracks that our brain puts together to form a multidimensional sound image. So that we can also hear them, the sounds that the device emits are long-wave and deep.

“You can consider the SomBat as an artistic project, as a musical instrument” says Hannes Hoelzl, who developed the device, “but for me it is really more of an apparatus with which we can train our auditory perception. In order to depict the space around us, similar to the bat, by means of hearing.” Hannes Hoelzl is a sound installation artist, electronic composer and lecturer for Generative Arts/Computational Arts at the Berlin University of the Arts (UdK Berlin). Otherwise he has little to do with bats. But a visit to the Atonal Festival in Berlin in 2017 gave him the idea of developing an instrument that conceptually continues the “SonDols” (Sonic Dolphins ) which the American avant-garde composer and experimental pioneer Alvin Lucier used in his piece "Vespers". These devices from the 1960s emitted electronically produced clicking sounds in order to communicate with dolphins – which was very much in keeping with the zeitgeist at the time. “SomBat is more universal. You can modulate different sounds with it and shoot them in a certain direction,” Hoelzl explains. And that works via a small, wood-panelled sound computer to which a megaphone loudspeaker is attached. The sounds can be triggered and varied via buttons and a joystick.

The bat imagery was part of the SomBat concept from the start. “Bats are representative of creatures that orient themselves acoustically via an echo-location system – like dolphins, whales or seals,” says Hoelzl. In contrast to humans, who can only hear long-wave, relatively low tones with frequencies up to a maximum of 20 kilohertz and thus go through life acoustically quite dulled, the bat hears very high tones in the ultrasonic range. These reach up to 100 kilohertz in its case. And it can also emit such high-pitched calls. “As a result, bats have a much finer spatial resolution acoustically and can also perceive objects in their environment that are millimetres in size – such as insects. In humans, on the other hand, the highest acoustic resolution is in the centimetre range. And that only at a young age,” explains Hoelzl. The large ears of the bats complement their orientation system perfectly, because they serve as a sound funnel.

To train people in spatial hearing – and therefore in acoustic vision – Hannes Hoelzl organises so-called “Sound Walks”. He moves with the SomBat through a wide variety of environments and uses the funnel to send sounds and noises in quick succession to corners, edges, arches and walls. The higher the tones, the more targeted they are and the smaller the surfaces on which they can reflect. The lower the sound, the more spherical the sound wave propagates.

The Sound Walks with the SomBat are all about the experience. “By means of this extremely simplified experiment, you get a clear idea of how complex the bat’s orientation is. Not only does it itself move very fast and tumbling through the three-dimensional airspace, but its prey are also fast and tumbling. It also has to avoid objects and enemies,” explains Hannes Hoelzl. At the same time, the SomBat performance is a realistic example of generative art, as researched and taught at the Institute for Time-Based Media at the UdK Berlin. An art form that focuses not on the product but on the process. This form of artistic creation also rejects media documentation, as is customary in scientific research. “Video recordings, for example, would close the process and thereby end it,” says Hoelzl and adds: “Artistic research has similar intentions to scientific research, but uses different methods. In scientific research, experiments are as comprehensible as possible, and they are usually carried out in closed systems. The result is then documented and published. What we do takes place in relatively autonomous processes and manifests itself, for example, in actions and individual experiences.”

Nevertheless, contacting bat researchers is one of the next steps that Hannes Hoelzl has planned as part of the SomBat project: “Berlin is the ideal place for interdisciplinary networking. It does not matter in which sector – you can find good and interesting people with whom you can work creatively everywhere. Berlin attracts them like a magnet. You can always address a community here.”

The Sound Walk is coming to an end. The sounds of the SomBat, which kept echoing through the outdoor space, attracted some curious people at their windows. Perhaps a sound image has now emerged in their heads – and they have thereby become part of the experiment. We will never know. That is also part of the concept. (vdo)

Hannes Hoelzl's home page (with SomBat sound samples)