Metallic noise from the hood

While driving in EV mode on bumpy roads, I've heard some metallic noise coming from the hood.
At first, I thought it was the hood itself, but at a closer examination I've excluded it because it rests on rubber supports while closed.
Maybe today I've found the source of the noise.
There's a felt-like rigid sheet under the hood. It's bolted on all sides except one, where it can vibrate against the hood.
I've placed a small wooden spacer to keep it in place.
I'll see in the next days if the noise will vanish.