Step 1: Please check the car radio frequency you adjusted is "Blank" frequency without frequency conflict (No working frequency and it is slight rustle white noise).
Step 2: Make sure you sync Bluetooth car adapter to same channel with car radio for minimized static noise ensure best sound quality, after sync the Bluetooth adapter with your car radio will be very quiet (If it’s still not quiet, try to find new BLANK channel again),then connect your phone with the product via wireless Bluetooth.
Finally: Adjust the volume of the car speaker, usually 50% is enough (never exceed 60%),The transmitter usually 70% is enough(never exceed 80%). We are not suggested you to adjust volume of your car speaker to maximum (that will bring lot noise).
Note: Please make sure your phone volume is at a maximum.
If you drive to different cities or states, Maybe you will have to change your station because stations might change with your driving.