@ DRUG MAFIA ....
Look at the image .... The Circles in red Show the holes from which the sound comes .... now c the blue circles by using the key provided wid the exhaust we can move the blue circled parts left and right ..... u can c the green line which is drawn in the path .... if we slide it towards the opposite direction from which they r right now .....the Red circled holes will close and the sound will be very less as the holes will be closed ...... And when we move them back to the previous location(Where they r right now) the red circled holes will be Opened as they r now ... and sound will be Powerful ........ u can set the holes at any size .... Though this is Volume control in Mufflers .... Hope now u get my Point