A display apparatus comprising: a signal receiver configured to receive a broadcasting signal; a display configured to display an image based on the received broadcasting signal; a sound receiver configured to receive a sound spoken by a user; a first sound recognizer configured to identify whether the received sound is a reserved word candidate; a second sound recognizer configured to identify whether the received sound is the reserved word; and a controller configured to: based on the display apparatus being in a standby mode, control the first sound recognizer to be supplied with electric power and to perform a basic sound recognition operation so as to identify whether the received sound is a reserved word candidate, based on the received sound being identified as the reserved word candidate, control the second sound recognizer to be supplied with electric power and to perform a detailed sound recognition operation so as to identify whether the received sound is a reserved word, and based on the received sound being identified as the reserved word control a preset operation to be performed, wherein the reserved word is a predetermined word for instructing the display apparatus to perform the preset operation, and wherein the reserved word candidate is a sound having a high probability of being the reserved word. a signal receiver configured to receive a broadcasting signal; a display configured to display an image based on the received broadcasting signal; a sound receiver configured to receive a sound spoken by a user; a first sound recognizer configured to identify whether the received sound is a reserved word candidate; a second sound recognizer configured to identify whether the received sound is the reserved word; and a controller configured to: based on the display apparatus being in a standby mode, control the first sound recognizer to be supplied with electric power and to perform a basic sound recognition operation so as to identify whether the received sound is a reserved word candidate, based on the received sound being identified as the reserved word candidate, control the second sound recognizer to be supplied with electric power and to perform a detailed sound recognition operation so as to identify whether the received sound is a reserved word, and based on the received sound being identified as the reserved word control a preset operation to be performed, wherein the reserved word is a predetermined word for instructing the display apparatus to perform the preset operation, and wherein the reserved word candidate is a sound having a high probability of being the reserved word. based on the display apparatus being in a standby mode, control the first sound recognizer to be supplied with electric power and to perform a basic sound recognition operation so as to identify whether the received sound is a reserved word candidate, based on the received sound being identified as the reserved word candidate, control the second sound recognizer to be supplied with electric power and to perform a detailed sound recognition operation so as to identify whether the received sound is a reserved word, and based on the received sound being identified as the reserved word control a preset operation to be performed, wherein the reserved word is a predetermined word for instructing the display apparatus to perform the preset operation, and wherein the reserved word candidate is a sound having a high probability of being the reserved word.