"The voice of the LORD..." The word voice in Hebrew, qol, is an onomatopoeic sounding of thunder itself. From the Word creating the worlds to the Word becoming flesh, the voice of the Lord tears through the cedar forest, yet blesses those who are His, those who hear the thundering voice and understand (not all do ~ St. John 12:28-9), with peace from His throne, on which He quietly reigns.
The thunder is, as St. Athanasius also says in On the Incarnation, our Father kneeling down to the level of our toddler eyes and clapping His hands to get our attention. We, distracted and consumed with anything but the still, small voice, are unable to hear Him, often enough, because His still, humble proclamation is drowned out in a sea of our passions. So He, condescending, thunders. Ours is a culture -- a rarity when one considers the scope of religious history -- that not only would have trouble hearing a non-thundering God, but also of hearing a God behind thunder. The qol Adonai, then, has not only to shake us from our distractions to Him, but also to shake us to Him and away from that which originally shakes us, lest we fail to see Creator behind creation.