Translation
He projected his voice loudly,
Go to footnote numberlike a lion’s roar, and when he spoke the seven thunders found their own voices and spoke up.
Paraphrase
He uttered commands with the authority of one to be feared,
and his commands were confirmed when all the powers of nature supported him.
Footnotes
1: "projected his voice loudly"
Authority is assumed here, even though it is not stated specifically in the original text. This is because there are only a handful of reasons for someone to shout or project his voice, and the giving of a command is obviously the one that fits the context. In order to give a command one must have the proper authority.