There is a well known iPhone SE problem with audio on certain Apple firmware. The firmware that affects audio is 9.3 and 9.3.1
The simple fix is to update the firmware to a newer version than 9.3.1 i.e. 9.3.2 and above.
This will stop the static or distorted audio sound, when using Bluetooth, such as in a car audio set-up.
Car makes affected by this issue include:
Audi, BMW, Chevrolet, Chrysler, Dodge, Ford, GMC, Hyundai, Infiniti, Jeep, Kia, Mercedes-Benz, Nissan, Subaru, Toyota, and Volkswagen.