Numbers 10:3

And when they shall blow with them
With both the trumpets, in an even and continued sound, that is, the sons of Aaron:

all the assembly shall assemble themselves to thee at the door of the
tabernacle of the congregation;
to hear what was to be said unto them: blowing both the trumpets together was a token that the whole congregation was called to meet together at the tabernacle, the door of which was the usual place of assembling, especially on religious counts, for there also the Lord met them, ( Exodus 29:42 Exodus 29:43 ) .