Problem probably lies in current working directory set by the QtCreator, with AFAIK (I had in past same problem) is diffrent then actual directory where bin is, use qDebug() << QDir::currentPath() to see what the working path is.

I tested Your code and it worked fine.
Try using full path i.e. /home/user/program/qt/program/sound.wav.
See if this file plays in external/native player if not install appropriate codecs.

AFAIK Error is related to the debugger, did You installed it?