"You listen to 'time' when you listen to music or the sounds of nature. And you listen to 'space' at a busy crossroad in Hong Kong loaded with traffic," he says. Hess' initial creative work had an unusual source of inspiration: the sounds of frogs - heard both in time and space.
"When I was young, I wanted to understand everything. I wanted to be Albert Einstein," says Hess, who spent his early life studying physics.
The physicist became fascinated by boomerangs, the simple yet effective weapons thrown by Australian Aborigines. So he moved Down Under, where he discovered ... frogs.
"In Australia, I lived in the hills near a small creek and every night I could hear hundreds of frogs calling to each other in a strange concert," he recalls.
"I was spellbound. I decided to tape-record them. It was very quiet at night and I sat very still. There were no scores or conductors. They just listened and responded to each other."
The vocal amphibians taught him, Hess says, "how to sit still and listen".
Back in The Netherlands, he set about making devices to imitate the sound of a live chorus of frogs. He completed his first machine in 1982, and since then, he has been building sound installations and exhibiting them around the world.
Just like frogs, his compositions interact with the environment, be it air, light, or people's movements. Hess aims to raise people's awareness and their sensitivity to their surroundings.
One of his works, It is in the Air, was featured at the sound festival.
"His artwork is an installation without sound," says student Cheung Wing-yan, 17, from Chan Shu Kui Memorial School. "When I saw the paper vanes on the floor respond to our movements, I 'heard' silence. It was like silence became a kind of sound.
"It taught me to look at things with a different eye."
Hess was invited to perform in Hong Kong, along with nine other local and international artists, by Yang Yeung, executive director of soundpocket, founded in 2008 by herself and a group of friends interested in the interaction of sounds with the environment.
"In Hong Kong, we seldom consider sound [as an artistic medium in its own right]," Yeung notes.
"If you listen to the songs on the radio, you'd wonder: Why are they all love songs? What about the [repetitive] music in restaurants? Our listening environment is monotone," says Yeung, who teaches at Chinese University.
Yeung sees listening as an acquired skill that is neglected by students today. "Students should learn to listen to each other and also to themselves. Like Hess said, 'Listening is about sensitivity'," she says.
Next Sunday, soundpocket is organising a public tour to "Otodate", an installation by Japanese artist Akio Suzuki. It consists of an ear and a foot print that will appear around Hong Kong, inviting people to stop, prick up their ears and listen to the sounds around them.
Visit www.soundpocket.org.hk for details