Comment by PMunch

As other people have pointed out "audio range" is generally 20Hz-20kHz. Your phone (and other audio equipment) is therefore built to be able to transmit those frequencies. The way a speaker creates sound is by passing electricity through a wire, creating a magnetic field, and pushing against a permanent magnet. Either the magnet or the wire is attached to a membrane that will then get pushed out. Doing this between 20-20k times a second and you make sound. However when charged particles (like the electrons in a wire) accelerate they create radio waves, so the magnetic coil in the speaker will also create a small amount of radio waves in the same frequency as the sound it is producing. This is what's called parasitic EMF, and in this case it turns out that this small amount of radio signal is enough to interact with the radio in the wheels.