Inaudible – Audible, Among the Bats

Sound sculpture at Rihemberk Castle.

The project bridges the gap between sound ecology and bioacoustic music. Sound ecology explores an almost inaudible sound environment for humans, while bioacoustic music incorporates sounds also from the inaudible frequency spectrum. The composition combines nocturnal human sounds with bat calls from the ultrasonic spectrum, processed and moved into the audible range. Bat calls are joined by other primarily nocturnal sounds with a background function. The final sound space encompasses the castle’s inner space, the distant forest, and the middle space represented by the outer plateau around the castle. The composition is played on headphones, providing a spatial (3D, 360°) ambisonic sound projection. This intimate and spatial experience avoids additional sound pollution of the natural environment at Rihemberg Castle.

The paesaggio sonorosound sculpture, its concept and realisation is the work of Boštjan Perovšek, a musician, composer and soundspace artist. He composes mainly experimental, electroacoustic music and specialises in creating bioacoustic music based on the sounds of animals, particularly insects. He also plays in the band SAETA and composes music for film, theatre, performances and multimedia installations. He is dedicated to the fusion of science and art and has made a significant contribution to the development of creation of soundscapes for public events, museums and galleries.

The sound sculpture will be played every full hour during the opening of the castle. The sculpture is 33 minutes long and it is intended for a maximum of 50 listeners at a time. The timetable of the castle is described in more detail on the Rihemberk Castle website.

Bat expert and consultant to the project, Klemen Koselj, wrote on this occasion:

A concert for four hundred furry babies and their mothers

What? Where can we possibly find so many babies in the area of the European Capital of Culture 2025 Nova Gorica - Gorizia? You would have to wait almost a whole year to get that many in Šempeter General Hospital. Well, most of them wouldn't be very furry. Only at Rihemberk Castle, where female bats gather in the spring to mate, nurse and raise their pups together. This is why the castle is extremely important for the survival of endangered bat species.

People don't realise that bats are true vocal virtuosos. Most of the time, they speak and sing in an ultrasonic sound that is too loud for our ears. Evolution has shaped their vocal cords and throat muscles to produce sounds at lightning speed, at the limit of what is physically possible, so that they can pick up the tiniest things in their surroundings in their echoes. In a single call, just a few thousandths of a second long, a fringe and twigged bat produces a rainbow of tones eight times as wide as the full range of human hearing. And bats use their calls not only to orient themselves, but also to communicate. Thus, every female bat returning to Rihemberk Castle from a night hunt recognizes her pup among the four hundred babies by its unique call.

These rich sounds were discovered by the composer Boštjan Perovšek, a pioneer of bioacoustic art. A sound sculptor who uses sounds from nature instead of marble. He teamed up with biologists, bat researchers, and used special equipment to record the sounds of bats, including the species listed above, and other sounds of the local landscape over two years in Rihemberk. He digitally converted the ultrasounds, which are inaudible to humans, into audible sounds. In the resulting work, Inaudible – Audible, Among the Bats, sounds from nature coexist with electronically generated sounds, just as natural and cultural heritage coexist at Rihemberk Castle. Coexistence is the only recipe for the long-term survival of humans and other species on our planet, including bats.

Don't miss the premiere of Inaudible – Audible, Among the Bats on 24 April at Rihemberk Castle as part of the European Capital of Culture 2025 Nova Gorica - Gorizia!

Photo: Boštjan Perovšek Personal Archive