John Gill Commentary Numbers 10:7

"But when the assembly is to be gathered together, ye shall blow, but ye shall not sound an alarm." — Numbers 10:7 (ASV)

But when the congregation is to be gathered together
At the door of the tabernacle of the congregation, and not to move in separate camps or bodies one after another:

you shall blow, but you shall not sound an alarm ;
blow with an even and uninterrupted sound, and not with a broken and quavering one; by which the congregation and camps were distinguished from one another, the same certain sound being given to each constantly, whereby they knew which were called to motion: see (1 Corinthians 14:8) ; according to Ben Gersom blowing was a voice drawn out, and joined or continued; an alarm, a voice not joined, but broken.