In the settings "app" of your iPhone is Spark listed, there you can optimize your settings for notifications.
Hi Sebastian.. thanks for the reply.. but there I don't see "vibration" option for notification even in the "app" setting
I reviewed my config and the Spark Client on Iphone uses the gernal settings for messages. I'm not sure wich message type inside "Settings -> Tones" is used for Spark (I have them all on Vibrate only).
Maybe playing around with this settings help. Important is that you enable "Tones" for Spark in the Notification settings