Had a similar issue this week. Definitely not an issue isolated only to iPhones as the background noise was during usage while paired with a Google Pixel.
I know this is an old thread but has anyone solved this problem so far? https://www.cargurus.com/Cars/Discussion-t76547_ds860819 I saw another forum had a thread about this with a solution. Has anyone tried a similar fix for the Clarity? Pohanka Honda of Fredericksburg Va fixed it for me. I have attached my service order that gives all the part number info on the audio unit. I can't say enough how wonderful the service manager, Mike, and the service reps were! They were determined to find the issue and not have me settle for just living with it! Okay, for some reason it's not letting me upload the photo. The cause is documented as an internal failure in the audio unit. 0101B5 Radio (Audio Unit) - Replace S/B 08-092 4518 WAR2; 1 39101-TLA-A42RM uNIT ASSY - , AUDIO; FC 03214: TECH LINE REFERENCE NUMBER 4054872.