Background: My Instrument Technician experience included vibration analysis of rotating equip. from 5HP to 5000HP, using accelerometers & microphone sensors. The vibration/noise data was evaluated with Vibration Analysis software that helped identify if the peaks at specific frequencies coincided with any of the rotating components, via balance, spalling, galling, resonance, etc. that were accumulated in a database of "vibration signatures".
The high pitched metallic sounds I heard from a contributors video, seemed to be resonance induced by the rich supply of ambient sources under the hood. A component, maybe a pulley or bracket or housing, is being excited or "rung like a bell". Why now with this XYZ damper/pulley change, could be as elementary as causing the engine to supply a different frequency source than existed prior. No doubt the low frequencies of engine component vibration were damped as designed, but that might have had a minor effect elsewhere. I agree the "sound" is annoying. Try [safely] to change some mechanical characteristics of the equipment under the hood, e. g. loosen a bracket bolt, placed some large rubber bands around the alternator housing, or power steering pump reservoir, etc.
"Estwing" manufactures high quality construction hand tools. Some years ago they suffered a PR hit, when a model of their steel shank claw hammers began failing, as the head cracked off! Very hard to imagine if you've ever handled one of those beauties. Long story [kinda] short, hitting framing nails supplied enough energy of the correct frequency to force the shank into resonance; it broke. They made minor changes to the shank geometry, changing [shifting] its natural resonance to a frequency not attained by hitting big nails.
Hope this helps someone.
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