וַיְהִי֙ ק֣וֹל הַשּׁוֹפָ֔ר הוֹלֵ֖ךְ וְחָזֵ֣ק מְאֹ֑ד מֹשֶׁ֣ה יְדַבֵּ֔ר וְהָאֱלֹהִ֖ים יַעֲנֶ֥נּוּ בְקֽוֹל׃
And when the voice of the horn waxed louder and louder, Moses spoke, and God answered him by a voice.
Read kabbalistic (mystical) interpretation of Exodus 19:19: and classical mystical sources.