[scrooched_moose]

Both of those are more shock events - there is a one-time impulse of energy into the system. The main difference here would be damping - the punching bag absorbs and dissipates the energy readily via internal friction of whatever the stuffing material is. A metal bell has orders of magnitude lower internal damping so it sits there and vibrates at its natural frequencies, emitting sound as it pushes against the air which slowly bleeds off energy due air resistance.

Random Vibration is usually characterized by a constant input of energy to the system at a range of frequencies - rocket motors, engine rpm + cylinder firing frequency, road noise, etc.

A somewhat imperfect analogy that I've heard is random vibration is analogous to playing white noise/pink noise/etc through a speaker. Shock is analogous to the horrific crackling and popping you get when you plug a guitar into an amplifier that's already on.