Remous literally translates to "eddies" or "whirlpools" in water, but it's often used metaphorically to mean "turmoil" or "commotion."
In this song, Aznavour sings, "La vie le monde et ses remous" (Life, the world, and its turmoil). He uses this word to describe the chaotic and busy aspects of life that fade away when he hears the voice of his beloved, emphasizing the profound peace and focus her voice brings him.
"J'entends ta voix" is a tender song about the moment someone's voice cuts through everything else.
Aznavour starts by describing the small, quiet sounds around him: his own heartbeat, a whisper, a footstep. Then, above all of that, he hears her voice, and it's like a door opening onto another feeling entirely.
From there the song describes what her voice does to him. It fills him with warmth, blurs his eyes, and leaves him lightheaded, and yet instead of feeling lost he feels like a king. He wants to shout, forget his good sense, sing at the top of his lungs, and climb onto rooftops, all because of the sound of her voice. It isn't about what she says. It's the pure, physical pull of hearing her speak.
The song ends quietly: the noise of the world fades away, and all that's left is the echo of her voice, still resonating inside him.