He has KU39 not KU36. Kumho aren't the 'best', they are a good low-mid-range tyre. They aren't that quite either. My Subaru came with KU22 and they were quite noisy, changed to Momo M3, quieter and grippier, but can go more quiet (will next round of tyres, gonna get Michelin).
OP, you may have some worn bushes?