Okay Guys
First thanks for your help, and as you said Morgan I have tried it with one wire which is TX of the Master to the RX of the receiver and a common ground I even powered the receiver Arduino from 5v of the Master Arduino.
What I can't figure out is that what character or number should I send using serial.read() and what to put on the serial.write().
I got confused because when I tried to send the mph (miles per hours) it doesn't let me compile it says invalid sending of array or something like that. When I tried to define a new character and then send that character to the receiver it doesn't do anything no sound at all I am guessing it is not sending anything.
If you look at my code there is something missing on the serial.read() and Serial.write() and the character or byte to be sent. I would appreciate if you help me there thanks a lot.