why does this radiator transmit sound from air into metal?

[Eiot]

i have this radiator, when i clap or scream the metallic rims start vibrating and transmit sound in metal. Why?

[swansont]

Sound will couple into a solid, especially if you are near a resonance. (Like if you yell at a tuning fork - it will vibrate) Also, since there are air channels, they can act as a guide and improve that coupling.