Audiologists have long expressed concern about hearing loss stemming from the use of headphones, but according to some, the new generation of digital music players pose a particular threat, allowing consumers to listen for long periods at high volume, and eliminating so much of the distortion and background noise common to, say, cassette players, that many listeners won’t even realize how much sound they’re pumping into their head. “Even with the sound piped directly into the ear canal, noise from the outside often competes with the music, and listeners turn it up louder. People listening to music while riding [commuter] trains, for example, frequently increase the volume levels to drown out the sound of the commute.”