well, while in Berlin we saw probably the nicest piece of audio installation art we have seen in quite a while, made by a couple of Dutch artists in 2000. It was shown as part of the transmedial media art festival, installed in the Parochialkircher, an empty, beautiful old stone church in the centre of Berlin. The acoustics there just added to the whole thing. I thought it was a complicated surround sound installation until I realised it was all reflections of the sounds blasting from this one, amazing machine that seemed to be alive and following you around.
below is a picture of it from a previous installation. just imagine this machine blasting out 100dB of electronic/staccatto/motorbike/machinegun pulses and static while spinning round angrily in response to something you did, in a huge church, under a spotlight and you start to get the idea…

some more info:
“SPATIAL SOUNDS (100dB at 100km/h)
‘Spatial Sounds (100dB at 100km/h)’ is an interactive audio-installation by Marnix de Nijs and Edwin van der Heide. Spatial Sounds (100dB at 100km/h) works with the effects of speed/ movement on the perception of audio.
Driven by engine-power Spatial Sounds (100dB at 100km/h) rotates a speaker mounted on arm of several meters. Like a watch-dog the machine is scanning the space looking for visitors. To investigate nearer is like challenging faith, the rotating arm swivels powerfully around. You hear the impressive sound of the mighty motor revving up. Faster and faster it turns around. You can feel the displacement of air when the speaker whizzes past, and you had better jump back, out of reach of the installation. The machine slows down and after the first shock you start wandering around. Exploring the space you manipulate the sound it produces…”
check out this website from one of the artists and look under works from 2000 for some brief quicktimes video of it in action. it actually spins really fast at times, and you feel quite physically threatened. The sounds, mapped from scanning its surroundings, are amazing…