From the SoundExtractor web site:
SoundExtractor lets you extract sounds from any kind of file and save them in System 7 sound file format, which can be easily played in the Finder with a double click.

Just open a sound suitcase or any other file (a game, for example) in SoundExtractor, or drag its icon on top of SoundExtractor's, and a new folder will be created. This folder will have a custom icon of a folder with a little speaker on it, and it will contain all the sounds that were contained in the original file. But now, double-clicking the sounds will play them!

You aren't restricted to sound suitcases: you can also extract sounds from applications, HyperCard stacks or other files. You can choose whether to look for standard sounds of type 'snd ' or other custom types, or sound data files.