The car won't turn on, but I can hear sound from the radio speaker. What is the reason ?

First, let's start with the source of the noise. The noise produced by the radio is mainly caused by the car's high-voltage ignition system, such as high-voltage ignition coils, distributors, spark plugs and other components, as well as various inductive loads , such as various car relays, motors and switch components caused by the produced electromagnetic radiation. Second, the radio itself has poor interference protection and will produce noise if the shielding is not good. You may consider installing a filter circuit, adding a magnetic ring to the wiring harness, or adding a ground wire to the shielding layer to reduce interference. There are many reasons why cars produce electromagnetic radiation. This type of electromagnetic radiation can only be eliminated or avoided by adopting good blin designding or replacing high quality radios. There's also the issue that the headlights are particularly bright when refueling, which may be due to battery drain. Additionally, when the engine is idling, the generator generates less power, so the headlights are dimmer. There may also be a problem with the generator's voltage regulator, causing the output voltage to be too high, making the headlights especially bright when refueling. Also, you mentioned that other lights flicker slightly when turning on the turn lights, which may be related to low battery voltage. It is recommended to go to a 4S store or regular repair shop for on-site inspection based on the above analysis.