I am noticing this buzz sound when I am lightly cruising in 2,3 or 4th. This buzzing resonance sound starts when I let go the clutch but goes away when I speed up. It sometimes gets pretty noticeably loud. It’s not engine or exhaust sound, it’s coming under the driver seat.

Thank you in advance for your help.

 

I didn't look at your video, but clutch buzz was a common phrase used to describe a noise which eminates from the trans tunnel into the cabin on AP1s. AP2s did not have this noise, if I remember correctly due to the added mass on the flywheel

 

Am I going crazy or is this the third time this video was posted with a different question?

Anyway, I can barely make out the sound. Do you mean that winding sound? I can hear it three times. It doesn't sound like clutch chatter, and it doesn't sound like a throwout bearing which tends to make more of a whirring or squeaking sound. How does your clutch pedal feel? Is it soft, like you can press it in with one finger, or is it stiff like it requires you pushing it with your whole hand? It'd probably be a good idea to use a stethoscope and listen to the bell housing to see if it's coming from the clutch or trans. That'd be the best way to diagnose it.

 

The clutch feels ok. This buzz resonance sound comes on between 3-4k rpm when decelerating. Foot off the gas pedal. Can hear it pretty noticeable in 3rd gear but you hear it from 2-4 gear, even a hint on 5th. It goes away when you accelerate. It’s very noticeable in cruising speed.

 

It's what everyone refers to as "clutch buzz" a quick Google search of "s2000 clutch buzz" will net you a multitude of results. I was wrong about the flywheel being the "cure" it happened with the oem clutch disc in early AP1s due to spring design originally which Honda fixed, but according to resident s2000 expert billman, it occurs with other non oem discs as well:

https://www.s2ki.com/forums/s2000-un...z-cure-985766/