Some competitors could cheat, taking advantage of using the head/earphones. For example, they could have an MP3 of a voice repeating an algorithm. However, I think it mostly applys to head/earphones. You can however, though you may not prefer, wear the head/ear phones without music playing.
Or, you can bring an iPhone to play music and set aside, as long as the volume doesn't disturb others. I think.
You can also chew gum, which has it's advantages.