How to set volume of phonon audio output

[athulms]

Musicvalue="Sounds/yellow.mp3";
    audioOutputmusic = new Phonon::AudioOutput(Phonon::MusicCategory, this);
    mediaObjectmusic = new Phonon::MediaObject(this);
    mediaObjectmusic->setCurrentSource(Phonon::MediaSource(Musicvalue));
    Phonon::createPath(mediaObjectmusic, audioOutputmusic);
    audioOutputmusic->setVolume(1.0);
    mediaObjectmusic->play();

Musicvalue="Sounds/yellow.mp3";
    audioOutputmusic = new Phonon::AudioOutput(Phonon::MusicCategory, this);
    mediaObjectmusic = new Phonon::MediaObject(this);
    mediaObjectmusic->setCurrentSource(Phonon::MediaSource(Musicvalue));
    Phonon::createPath(mediaObjectmusic, audioOutputmusic);
    audioOutputmusic->setVolume(1.0);
    mediaObjectmusic->play();

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But there is no change in volume