Dear Fabrice,
This is where blueprints become very handy!
~Whatever class you need to call the sound cue in, in the .h file, put this there:
/** Your Sound Comment */
UPROPERTY(EditDefaultsOnly, Category=Sounds)
USoundCue* YourSound;
Make sure this is in the public section or near very top of class definition
~Then compile
~then go into editor and blueprint your class that you just ededited
~then drag your soundcue into the blueprint’s default properties
~you can reference the blueprint using your findobject method or by using a UPROPERTY like above and using (UClass*)
I usually inter-reference my class instances if I need to set a lot of properties like this, so that one Blueprinted master actor is the one where I put all the sound cues or other asset information, and then reference that master actor any time I need the assets
Enjoy!
Rama