Audio level safety limits and their impact on personal music player

Personal music players have become very common in the past decade, yet we haven't had time to see the cumulative impact of higher audio levels for longer durations on the hearing of the general public. A number of industry and governmental organizations are interested in setting audio safety limits before a large number of users risk hearing damage. Much of the existing research and regulation for safe audio levels is based on occupational exposure, yet these limits are often used as the basis for proposed audio limits for personal music players. Occupational limits are based on a fixed intensity for a defined period which is not necessarily representative of audio played on personal music players. Regulations imposed for the safety of one type of user may prevent the music player from being adequately used by listeners of other types of audio programming. This paper will look at a number of topics covering audio safety. It will discuss the basic mechanisms of audio induced hearing damage. Next, it will look at existing sound level regulations and proposed regulations along with the potential impact of those regulations. Next it will cover audio level measurement methods for personal music players, the applicable standards defining those test methods and the impact of different headphones on those measurements. Finally, it will cover the audio level profiles of different types of programming frequently played on personal music players. Using this information, various scenarios will be discussed for limiting audio levels and the risk of hearing damage from personal music players. These techniques range from a fixed maximum audio level through user acknowledged overrides to real-time dynamic level sensing and control.