An analogy is given to explain the sounding of the shofar on Rosh Hashana: There was once a king who sent his only son to a distant land to learn about its peoples and customs. As time passed, the prince's royal garb became faded and torn, and he even forgot how to speak his native tongue.
One day the prince heard that his father, the king, would be visiting the region. "How will I be able to approach him?" he thought to himself. "My clothes are torn, and I cannot speak the language."
The son decided that he would simply call out to his father in a cry without words, emanating from the heart, which the king would surely recognize. This is the call of the shofar, which appeals to the King's very Essence. (The Baal Shem Tov)