Unlike phones, which are commonly held to the ear, music is now available via portable MP3 players and they can be held almost anywhere. Thaker et al state that Apple iPods cause pacemaker interference in 50% of their patients, with over-sensing in 20% of patients, telemetry interference in 29% of patients and pacemaker inhibition in 1.2% of patients. The mean age for their sample was 76.1 years +/- 8.6 years. We anticipate that a higher proportion of teenagers and children who have pacemakers use portable MP3 players than in the elderly adult population.We will include the first 100 patients with pacemakers and ICDs who consent for the prospective observational study a single tertiary care center. We intend to conduct a descriptive study, tabulating the number of times that a pacemaker or ICD has changes in the sensing thresholds, pacing thresholds, telemetry interference or pacemaker inhibition when exposed to a series of portable MP3 players at various distances. In addition, we will describe the nature and quantitative differences of those changes.