
However, iPod manuals already state it clearly that using player's headphones at high volume levels can potentially cause permanent hearing loss. The complaint tries to override this by stating that Apple did not advise users about what constituted a high volume or a safe level of noise.
As a sidenote: the first portable audio player, that produces the same effect as iPods -- high audio levels via headphones, was called Sony Walkman and was first sold in 1979.
Source: Financial Times