How did people know when was going to begin? The Gemara relates:
The school of Rabbi Yishmael taught: Six blasts are sounded on eve. When one begins sounding the first tekiah, the people standing and working in the fields refrained from hoeing, and from plowing and from performing all labor in the fields. And those workers who work close to the city are not permitted to enter the city until those who work farther away come, so that they will all enter together. Otherwise, people would suspect that the workers who came later continued to work after the blast. And still, at this time, the stores in the city are open and the shutters of the stores, upon which the storekeepers would arrange their merchandise in front of the stores, remain in place. When he began sounding the second blast, the shutters were removed from where they were placed and the stores were locked and in the homes, however, hot water was still cooking on the stove and pots remained in place on the stove. When he began sounding the third blast, the one charged with removing food from the stove removed it, and the one charged with insulating hot water for so that it would not cool off insulated it, and the one charged with kindling the lights lit. And the one sounding the shofar pauses for the amount of time it takes to fry a small fish or to stick bread to the sides of the oven, and he sounds a tekia, and sounds a terua, and sounds a tekia, and accepts.
The shofar blasts advising the people of the imminent onset of had to be heard throughout the city of Jerusalem and beyond, especially by those working in the fields. The Gemara, though, does not identify the location from where the shofar blasts were sounded. Josephus refers to the spot as being on one of the towers of the Temple (Wars of the Jews 4:9:12). During the archaeological excavations conducted adjacent to the Western Wall in the wake of the Six-Day War, a large stone was discovered at the southwest corner of the walls surrounding the Temple Mount, with the inscription: “To the trumpeting place to…” Apparently, it fell from a tower atop the wall and shattered during the destruction of the Temple by the Romans in 70 CE.