A study done in Manchester, Birmingham and Brighton, England, found that the average listening device user typically turned up the volume to above 85 decibels, which can lead to hearing loss. That many decibels sustained over the course of one hour has come to be recognized as the maximum level of sound that is healthy for the human ear.

Another study in the United Kingdom found that most users of personal listening devices (such as the iPod) don't know the guidelines for healthy listening. The combination of intense loudness from in-ear phones and long-term use are the main culprits in hearing damage. The same study found that keeping sound levels to 60 percent of maximum and not using earbuds for more than 30 minutes a day can prevent substantial hearing loss ("Les Ecouteurs Sont-ils Dangereux Pour L'Ouie? [Earphones, Are They Dangerous to Hearing?]," Le Figaro, Oct. 3, 2007).