Ios-how to implement custom vibration pattern programatically

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iPhone

iOS

In my app i want to bring in custom vibration.In my code i have used the code to implement the vibration.But the problem is the vibration intensity is very high and When i try to reduce the intensity the feel of the vibration is missing.Need any suggestions for bringing a minimal vibration programatically.

What I have tried:

Added the AudioToolBox framework.
This is the code for vibration to occur.

AudioServicesPlayAlertSound(kSystemSoundID_Vibrate)

This produces only the default vibration.