Besides his visual works of art, Klaus Osterwald has been collecting a variety of sounds for many years, and has used them in his sound installations. His conception
of an artistic "bugging operation" was worked out in his project DONATUS SUBAQUA in 1998 and is still growing constantly. Based upon the knowledge that fish communicate
acousticly, he constructed his own hydrophones to make sound recordings in a in a debth of up to 12 m in a little lake near the city of Cologne.
Osterwald was surprised that his recording equipment was able to document such a huge variety of underwater sounds. There are sounds of the underwater environment
like gas bubbling up from the bottom, plants producing oxygen, insects and even the calls of waterboatmen. But there are also very mysterious "voices" on the tapes,
which could not be identified up to now even though O. confronted some zologists with his acoustic discoveries . The research on the origins of the "underwater-voices" of Lake Donatus has become a constitutive part of the art project DONATUS SUBAQUA, which Osterwald
presented in a several exhibitions in Germany, South Korea and Great Britain. In his installations the sounds emerge from large horn-shaped speakers from cast aluminium,
hanging at the ceiling. Each hornspeaker' softly sends one of the mysterious "voices".