Psalms 89:15 - Coke's Commentary on the Holy Bible

That know the joyful sound— This probably refers to the trumpet, which was always used by the express command of God at the Jewish festivals. And as the ideas in the preceding verses are taken from God's deliverance of the people from Egypt, and his august appearance on Mount Sinai, where the awful trumpet proclaiming his presence was heard; so here the joyful sound may refer to that trumpet, which in the public worship, as heretofore on Mount Sinai, proclaimed the approach of God, and summoned the people to his worship. The ideas in the following verses have the same reference. Compare Numbers 23:21.