Yes mine does it too and for the price of the device I'm surprised. I've tried multiple aux cords myself and they all have the same static feedback noise through the speakers
Sadly enough, these devices cost a small fortune so much so, that they offer payment plans to sell them. The only noise I've experienced on my S8+ is the ground squeal coming through the car speakers with an auxiliary cord, even the most expensive. However, I read somewhere that I could attach a device called ground loop isolator. You plug the auxillary into your phone and connect the ground loop isolator between the auxillary male and female. Problem solved. I was able to use hands free, but I would have to yell.
Then I discovered Soundbot 360. It's a beautiful thing. It's everything you want in Bluetooth and hands free. Yes, you will still NEED the ground loop isolator.
Found the solution. At least it worked for me. In the setting menu, go to sound and vibrations. Then scroll down to sound quality and effects. Enable UHQ upscaler and the ridiculously horrible static went away. Hope it works