iOS local notification sound is overlapping on a locked screen

Question

I am working on alarm application. I had used local notification to notify user, it's working fine when application is in foreground or in background but when I locked the screen at that time notification arrived but notification sound is overlapped. Overlapped issue occurred only when device is locked.

I am referring Alarmy app which is live ans working fine in same scenario even it's also play sound when device is silent mode.

I had also refer asked question related Alarmy App but it did not help me.

I am stuck in this issue don't know what to do because it's playing sound without overlapped when screen is not locked. And I can't play any sound through code when local notification arrive, ringing sound completely depend local notification.

Below is code by which I'm setting local notifications,

func add(alarm: Alarm) -> Void {
    UNUserNotificationCenter.current().removeAllDeliveredNotifications()
    UNUserNotificationCenter.current().removeAllPendingNotificationRequests()
    
    let identifier = "\(alarm.id)"
    let content = UNMutableNotificationContent() 
    content.title = applicationName
    content.body = alarm.label
    content.categoryIdentifier = identifier
    var dict = [String: Any]()
    dict["id"] = alarm.id
    dict["sun"] = alarm.sun
    content.userInfo = dict
    content.sound = UNNotificationSound.init(named: UNNotificationSoundName.init("\(alarm.soundName).wav"))
    
    let interval = Date.init(timeIntervalSinceReferenceDate: TimeInterval.init(alarm.time))
    var i = interval.timeIntervalSince(Date())
    if i < 0 {
        i = 1
    }
    
    for t in 1...60 {
        let triggers = UNTimeIntervalNotificationTrigger.init(timeInterval: i + 6, repeats: false)
        let requests = UNNotificationRequest.init(identifier: "kathla\(t)", content: content, trigger: triggers)
        UNUserNotificationCenter.current().add(requests) { (error) in
            if let error = error {
                print(error.localizedDescription)
            }
        }
        i = i + 5
    }
}