A knob assembly includes a head portion and a cylindrical-shaped protruding portion protruding from one surface of the head portion. The protruding portion is interlocked with and configured to rotate together with the head portion. A plurality of friction protrusions are disposed along an exterior circumference of the protruding portion and configured to generate friction sound patterns by sequentially rubbing an external protrusion as the head portion rotates. A fixing member is coupled to the protruding portion in an opposite direction of the head portion.