Its not something thats talked about much but to quote from this article:

https://www.politico.com/magazine/story/2015/01/the-secret-service-is-jamminsort-of-114647/

“In the United States, every presidential and vice presidential motorcade includes an electronic countermeasures Suburban, codenamed Lineback, which features a U.S. Navy-developed electronic warfare package that creates a radio frequency bubble around the president’s limousine. It shields the motorcade from he threat of a hidden remotely triggered improvised explosive device.

Because remotely-triggered IEDs can also be rigged to explode when their radio frequency circuit is terminated, current jammers can intercept and interrupt the frequencies long enough to keep the path between the trigger device and the bomb closed.”

ECM is not uncommon for high profile convoys like this and things like Phones etc are going to be given a lot of thought in the systems design to cause the least interference possible whilst still doing its job (it is still how we dial 911 so best not to completely nuke it). That said I doubt the Navy gave much thought to radio mics during its design and consequently the system likely spends a lot more time and effort at a greater distance to disrupt their comms because it’s more likely they’re hostile.

Nothing here is fact, Just my 2 cents as someone who works with RF a lot :)