'Send ``volume_changed`` event to all mixer listeners.
This method should be called by subclasses when the volume is changed,
either because of a call to :meth:`set_volume` or because of any
external entity changing the volume.'

def trigger_volume_changed(self, volume):

    logger.debug(u'Mixer    event:    volume_changed(volume=%d)', volume)
    MixerListener.send(u'volume_changed', volume=volume)
