Charles Ellicott Commentary Numbers 10:2

"Make thee two trumpets of silver; of beaten work shalt thou make them: and thou shalt use them for the calling of the congregation, and for the journeying of the camps." — Numbers 10:2 (ASV)

Of a whole piece. —Better, of beaten (or, turned) work. (See Notes on Exodus 25:18; Exodus 25:31.) The trumpets spoken of here are supposed to have been straight, like that on the triumphal arch of Titus at Rome and on the old Egyptian monuments. In this respect, the hazozerah is supposed to have differed from the cornet or horn, keren or shophar (which is interchanged with keren), which was crooked. (See Joshua 6:5, compared with Joshua 6:4, 6, 8, 13.)

We find a reference to the jubilee trumpet in Leviticus 25:9, from which it has been inferred that the trumpets mentioned here were not first made at this time. It is true, indeed, that the first verse might be rendered: Now the Lord had spoken unto Moses, saying; but the word used in Leviticus 25:9 is shophar, not hazozerah, and the latter word occurs in this place for the first time.