1. We are given 4 files: "10kg Down and Up" and "20kg Down and Up" respectively. We can open these couples via SonicVisualiser.
2. Next step is to impose a Layer. Layer->Add Spectogram.We must notice that the symbols are like letters.Connecting in each pair the lower and upper symbols in each pair, we get Gosqrd Romnz.
3. Just decode this in the variations of the rotations cipher.. Gosqrd in rot16-> Weight Romnz in rot20-> Light Light Weight is a popular phrase of Ronnie Coleman.(From the conditions of the assignment it becomes clear).

Flag: VishwaCTF{Light_Weight}.