let storageRef = storage.reference().child("Audio").child(successFileName)
    self.titleLabel.text =  self.successTitlename

    SwiftSpinner.show("Loading...")

    storageRef.downloadURL { url, error in
        if error != nil {

            SwiftSpinner.show("Couldn't load Audio...Tap to dismiss").addTapHandler({
                SwiftSpinner.hide()
            })
       **Getting error here**
            storageRef.observe(.progress) { snapshot in
 // Download reported progress
    let percentComplete = 100.0 * Double(snapshot.progress!.completedUnitCount)
                    / Double(snapshot.progress!.totalUnitCount)
            }