"And the sound of the shofar, very strong" (Exodus 19:16) — the Mekhilta connects this to a later verse (Exodus 19:19): "And the sound of the shofar grew exceedingly strong." Together, these verses describe something that defied every law of nature the Israelites had ever known.
Under normal circumstances, the longer a sound is sustained, the weaker it becomes. A trumpet blast starts strong and fades. A human voice grows hoarse. Every sustained sound in the natural world follows the same trajectory: loud to soft, strong to weak, forceful to faint. This is simply how sound works — or how it worked, before Sinai.
At Sinai, the shofar's sound operated in reverse. The longer it was sustained, the stronger it grew. Instead of fading, it intensified. Instead of weakening, it built. The sound did not diminish with time — it multiplied. What began as a strong blast became stronger still, then exceedingly strong, then beyond anything the people had experienced.
The Mekhilta explains the purpose of this supernatural progression: in the beginning, the sound started at a manageable level to accustom the ear. God did not assault the people with the full force of divine sound all at once. He allowed them to adjust gradually, letting the sound build so that their senses could adapt to what was coming. It was an act of mercy embedded within an act of power.
The final phrase records the people's response: "Vayecherad all the people in the camp" — they were shaken. Not merely frightened, not merely startled, but physically trembling. The sound of the shofar at Sinai shook the Israelites to their core, and it did so precisely because it defied everything they thought they knew about how the world worked.