Increasing the volume of your iPod isn't simply a case of pressing the "volume up" button. Two different settings may limit the volume regardless of the changes you make with the volume control. As well as changing these settings, you can get louder playback through external devices.
ITunes includes a feature called Sound Check that is designed to make sure all songs in your library play at roughly the same volume; this feature changes individual file data, in turn affecting the volume of the songs on your iPod. While the feature may be useful if you have lots of songs recorded at differing levels, it can be annoying if it means songs you enjoy hearing at a particularly high volume are quietened to fit in with the rest. You can turn off Sound Check in the Playback section of the iTunes Preferences menu. The next time you restart iTunes and then sync your library to your iPod, the songs should return to their original volume.
Apple's audio devices, including the iPod, iPhone and iPod Touch, have a setting that enables you to designate a maximum volume that overrides the data for any individual track. With all models except the iPod Shuffle, you can change this setting in the Settings menu on the device itself. On the iPod Shuffle, you must connect the iPod to your computer, then change the "Limit maximum volume" setting that displays in iTunes. On some models of iPod sold in Europe, you may see an on/off setting for "EU maximum volume"; if turned on, this setting automatically limits the device volume to the maximum level recommended as safe by European Union officials.
IPod Docks and Speakers
Plugging your iPod into an external device with its own amplifier can let you hear music at a louder volume than through headphones or an iPod's built-in speaker. Exactly how the volume control works depends on your combination of devices. Generally, if you are connecting through the iPod's headphone socket, you can control volume in the speakers through a combination of the iPod's own volume controls and those of the external speakers. Increasing the iPod volume controls to full blast rather than increasing those on the external device may reduce the power consumption of the external device, but could cause audio distortion. If you are connecting through the iPod's dock port (the socket you use for connecting via USB to a computer), you'll sometimes control the volume solely through the iPod itself, or sometimes via buttons on the dock device or a remote; either way, you'll usually only have one volume control available.
Listening at high volume can seriously damage your hearing. The risk isn't solely a matter of how loud the music is, but also the length of time for which you are listening. Remember that the volume settings on your iPod, including the Volume Limit feature, only affect the output to the speaker socket. The actual volume you experience, and in turn the potential risk, may depend on the specific earphones you use. In-ear models may let you get the same clarity at a lower, safer volume.