Several ideas are offered:

1) This is a clear signal to all that Yom Kippur has concluded; it is also reminiscent of the Shofar blast after the 10 Commandments were given that indicated it was now allowed to ascend Har Sinai. 2) By sounding the Shofar now, we complete the 40-day period of introspection & Teshuva that began with Shofar-blowing on Rosh Chodesh Elul; 3) The Shofar’s triumphant, clarion call indicates our belief that our prayers have been answered in the affirmative & that we have been granted a new lease on life.

The story is told of a country boy who visited the big city. Suddenly, while walking around, he heard the sound of a bugle being blown from a high tower; a fire had been spotted! Immediately, a "bucket-brigade" was formed, water was passed from hand-to-hand, & soon the fire was put out. The boy was greatly impressed, & he bought a bugle. He returned to his village & called all the people to come around him. He then threw a match on to the roof of one of the thatched houses. The people were aghast, but the foolish lad told the people not to worry. He took out his new bugle & began blowing and blowing, but the fires soon spread to the whole town!

It is the action we take during these days, you see, and not a mere Shofar-blast, that is the real key to Teshuva.