Sony Xperia Z - Turns onto vibrate mode whilst making a call.

[Beth Barnes]

Curious to know why when I make a phone call or receive phone calls my phone turns on to vibrate mode during the call? and stays on vibrate mode until i manually turn it back on to loud?
can anyone resolve this? as it is a pain changing it back all the time.

thanks

 

[dmchospital]

Same problem with my samsung s4 android.