Samsung galaxy s4 long vibrate time on 'vibrate' mode.

Samsung galaxy s4 long vibrate time on 'vibrate' mode.

I have Samsung Galaxy s4 - GT-i9500, running Android 4.2.2.
Im using Facebook messenger to chat with my friend on Facebook.
When Im on 'vibrate' mode, when I get notification, it's like one long
vibrate, instead of two short vibrates. (as was in my Galaxy s3)
it's very annoying. Any suggestions how to get back to the '2 short
vibrates'?
in' sound' mode, I get the normal case - 2 short vibrates. Thanks!