Yet another rattle thread

[buenor]

But I have searched and I have not found a description of a rattle that's similar to mine, so hopefully I did not miss a really obvious thread.

I have a buzzing (like a plastic cable or sorts) that seems come form under the left side of the dash. Nothing seems loose the top and I have tried to tighten/retighten everything on there (no difference). The buzz comes up when the engine is accelerating slowly around 1500-2000 rpm. Of course, most of my city driving happens to be in that range. I can hear the same sound when I drive of slightly rough pavement but it is less loud (very much the same sound/approximate location) .

Does anyone have any suggestions as to the possible source? It's otherwise a pretty low rattle car (except over bumps, ha ha).

Thanks in advanced.