"And all the people saw" — the sounds of sounds and the flames of flames. The Mekhilta asks: how many sounds were there at Sinai, and how many flames? The answer is not a specific number but a principle: each person heard according to his own power to absorb the experience.
The proof is (Psalms 29:4): "The voice of the Lord in power, the voice of the Lord in majesty." The psalm does not say "in His power" but "in power" — without a possessive pronoun. The rabbis interpreted this to mean: in the power of each individual listener. God's voice at Sinai was not a single uniform broadcast. It calibrated itself to each person's capacity.
An elderly person heard one thing. A young person heard another. A child heard according to a child's understanding. The same divine utterance registered differently in every mind and heart that received it. The sounds multiplied into "sounds of sounds" and the flames into "flames of flames" — an infinite cascade of revelation, personalized for every Israelite standing at the foot of the mountain.
This teaching has radical implications for the nature of revelation. The Torah was not given as a single fixed message that every person received identically. It was given as a living communication that adapted to its audience. The voice of God was simultaneously one and many — unified in its source but infinitely varied in its reception. Every person at Sinai received the Torah they were capable of receiving, and all of those receptions were equally valid.