I'm getting this buzzing sound from the engine (or maybe deep under the dash, it's unclear to me) between 4000 and 5000 RPMs on my 2005 S2000. It happens both under throttle (accelerating), and off-throttle (decelerating). It also appears to happen even when standing still and revving the engine, though it's quieter in that situation.

Oddly, it's also MUCH easier to hear with the top up - with the top down, the sound is still there, but much more subtle.

Has anyone had anything like this? Is it something serious, or just something insignificant vibrating bit that hits some harmonic frequency and starts rattling between 4 and 5k? Note that it stops happening after 5000 rpms, and sounds fine going up from there to redline.

Thanks!

 

sounds like something got stuck or it's the heat shield...

 

This started happening to my '06 recently. As it turns out, it's the shifter thats buzzing. You may have the same issue. If you do a search with those keywords, you'll come across others with the same problem, as well as the fix.