All damping materials have different characteristics at different frequencies, so choose your treatment intelligently or recruit a consultant to assist you. Isolation is defined as a method of detaching or separating the vibration from another system or body. Isolation by definition does nothing to reduce the vibration magnitude, it simply seperates the vibration from the system you wish to protect. Some materials may actually perform damping and isolation functions at particular frequencies, but the words are very different and often confused. All materials for isolation perform differently at different frequencies, and if chosen incorrectly, may worsen your problem, not improve it.
Barriers perform a blocking function to the path of the airborne sound.
A closed door is a simple example of a noise barrier. Barrier performance is strongly correlated to the openings or air gaps that exist after the barrier is employed. If your door is only closed half way or there is a large gap under and above the door where sound may travel through, then your door will be far less effective at blocking sound. If there are no air gaps when a barrier is employed, then weight becomes the dominant factor in comparing barriers. Doubling weight typically reduces sound transmission by 6 dB based on the Mass Law.