A display apparatus includes a display part to display an image thereon, a speaker to output sound, an audio input part to receive an audio signal, an audio signal processor to process the audio signal input from the audio input part through the speaker and to output the audio signal, a control signal output part to output a predetermined control signal, a detector to detect whether the audio signal is input through the audio input part, and a controller to control the audio signal processor to control the audio signal according to the control signal from the control signal output part if the audio signal is input by the detector, and to control display conditions of the image displayed on the display part according to the control signal from the control signal output part if the control signal is not input by the detector.