This Roll20 API script will play a sound effect any time a player rolls critical hit or a critical fail. This script is compatible with the Shaped 5e character sheet macros.
##Setup: Install the script on Roll20, then select 2 sounds in the Jukebox.
Name one sound 'Critical Hit' and the other 'Critical Fail'.
The script will automatically play these sounds when a player rolls a natural 20 or natural 1 on a d20.