What are these things on the engine cover?

[freaknbigpanda]

I had my interior out for the first time recently to install some sparco race seats and harnesses, as well as get a smog, and I noticed these flexible metal strips with adhesive on the back stuck to my engine cover:

IMG_6951.jpeg (773.23 KiB) Viewed 251 times

the one on the far left flew off during my last track day, found it in the trunk. so i stuck it back on. guess the wind at 140mph was too much!

[Ric_in_RVA]

Looks like a Dynamat type sound deadener. Surprised it flew off. Maybe the heat loosened the adhesive.

I've coated my covers with Dynamat. Not sure it did anything but add weight....maybe drop a little resonance.

[dr bob]

"mass loading" is a technique to stop resonant noises, where you add weight at the center of a vibration node to move the natural frequency. Usually lighter than adding rubber to the whole panel, which does add quite a bit more weight vs. the selective changes with smaller pieces, as @Ric_in_RVA describes. Finding all the resonant nodes in a section can be tedious, as it's an iterative and very interactive process. The results vs. the full panel are similar, just trading the weight for time saved if you are doing it yourself.

[freaknbigpanda]

Ah OK got it, since the one on the far left flew off during my last track day I'll have to track down where it was placed in the car. Hopefully there is some residue that can point me in the right direction