Most of the dampener are used to absorb the vibration (or the "ping" sound you can hear) of the string ONLY. It is nothing to do with the shock created from the racket. Different sizes and types of the dampener provide different levels of dampening effect. Usually, bigger and softer dampener absorb more vibration. The position the dampener installed also affect the dampening effect. It absorb more vibration when it is in a higher position of the string bed.
In fact, the string vibration (sound) from the string is the feedback from the string and racket. If it is absorbed, you will get more solid feel but less feedback. So, do some experiment and find your preference!