I can't imagine putting smaller tyres on will foul anywhere making a noise, but 185/65/15 are over 4% smaller diameter than 205/65/15, the sidewall size reduces as the tread width reduces lowering gearing etc. I don't know how far you can go without upsetting the ABS system, it likes all the wheels spinning at the same speed. That said, I'd guess noise is more likely mechanical. What size were they originally? Were these tyres already on wheels when you got them, and if so are they the correct offset?