At the Henry Art Gallery, the sweet sounds of — the AC system?

In one room: white noise with an almost subsonic throb to it.

In the other room: a higher resonance, approaching but not quite reaching gamelan-chime or church-bell reverberation.

Now installed at the Henry Art Gallery, "+Room — Room" is a collaboration between sound artists Jamie Drouin, of Victoria, B.C., and Yann Novak, a former Seattleite based in Los Angeles. There's nothing to look at here. The whole point is to highlight sounds that we "typically filter out," the artists say.

The two men's sound sources, recorded last summer when the museum was closed, are the Henry's air-conditioning system and, they argue, the building's architecture itself. Novak added resonance, extending the ventilation system's "notes" while allowing it to "still have its own voice." Drouin subtracted elements, with a muted result that, he says, is "almost like you're hearing the lighting."

The recorded sound, intended to interact with live ambient sound in the gallery, is barely audible to a casual gallery visitor. Drouin says he and Novak were after "a subtle experience" with their staggered 30-minute loops of sound that gradually go out of phase over the course of a museum day.

If the subtlety of an hourlong exchange between live ambient sound and recorded noise-manipulation isn't your bag, you can also experience "+Room — Room" as a CD ($10 at the Henry's gift shop). It makes for a nicely trippy headphone experience.

Michael Upchurch: mupchurch@seattletimes.com