Whirring noise in neutral when clutch pedal released. What is it and how to fix?

What is your question?

I recently replaced the clutch master cylinder and manual transmission fluid (MTF was an aftermarket brand but recommended weight) on a new to me 60k mile 2006 Honda. Afterward, I noticed a whirring after starting the car when I released the clutch pedal. The whirring sound goes away when I press the clutch pedal. The sound improves but doesn't go completely away when the car is warm, and I don't notice anything when the car is in motion or in driving, the clutch pedal may have a little more freeplay than others of the same model I've driven. The sound may have been there before, I'm not sure, but it's definitely worse now.

What makes this problem better or worse?

worse when engine is cold

How long has your 2006 Honda S2000 had this problem?

Noticed it after recent changes, may have been there before but less obvious