SciTech

How Things Work: iPods

The digital music player has become a staple of everyday life for many college students. Apple’s iPod accounts for the majority of MP3 players sold worldwide.

To better understand the iPod, we need to explore musical recordings themselves. Live music, typically heard at concerts, is thought of as analog, which is a continuous variation of frequencies that produces a desired sound. Older stereos used analog technology.

But in the new world of electronic gadgets, the iPod is classified as a digital music player. It is called digital because the music files stored on the iPod are in digital form, meaning that the files are mathematical samples of the original analog wave.

Digital MP3 files are actually just representations of the original sound produced from the music’s studio recording. MP3s are successful because they use an efficient compression technique to store a lot of data into a small amount of space. They discard fewer audible sounds and can be recorded using different bitrates. This gives MP3s flexibility in size in relation to audio quality. The iPod allows users to take digital music and reproduce high-quality sound.

There are seven primary components in most iPods: the hard drive, battery, touch-sensitive click wheel, LCD display, microprocessor, video chip, and audio chip.

The hard drive inside an iPod has advanced sensitivity technology to allocate almost 100 gigabits, or roughly 3500 MP3 songs, per square inch.

The iPod’s iconic click wheel is similar to laptop touchpad technology. There are five normal pushbuttons under the click wheel that control file selection and playback. When pressed, the buttons complete a corresponding motherboard circuit. The circular pad allows users to scroll through the menus and files on the iPod. Under the plastic surface is an underlying metallic channel membrane that creates a grid system. Electrical currents are sent through the grid.

When a conducting surface (finger) is near the grid, a charged capacitance builds up on the grid. Information is then sent back to the click wheel controller chip, which senses changes in capacitance on the wheel.

The controller chip is a mixed-signal array, meaning that it takes analog signals (capacitance changes) and translates them into digital signals for the microprocessor. It also responds to motion speed. The faster the motion on the wheel, the more compressed the stream of signals becomes. The wheel stops sending signals when there is no motion detected, thus stopping scrolling on the screen.

The LCD is a thin film transistor, which gives precise control over the display elements on the screen, allowing rich, 16-bit color.

The microprocessor and chips are relatively small and allow for a compact motherboard layout with hundreds of tiny, electronic interconnections. There is also onboard SDRAM, typically around 32 megabytes. This allows faster access to files and better playback on the iPod.

Besides hardware, an iPod relies on its software. The current generation iPod uses the Pixo OS 2.1. The software helps decode music and video files to play back to the user.

No media player is complete without its computer jukebox software. The iPod uses iTunes. iTunes uses an autosync feature, which automatically detects whether an iPod is connected to the computer.

It also automatically downloads any new iTunes content to the iPod.

However, the software can force the iPod to match the iTunes library. iTunes can wipe any new MP3s from the iPod if they were not transferred through iTunes when autosynching, unless specified in iTunes preferences. Simply, the iTunes software detects an iPod and synchronizes the iPod’s library with its own library.

The iPod’s compact and sleek form resulted from years of design work to more effectively house its various micro-technologies. Though many other digital players on the market employ similar features, the iPod remains the best-selling digital player today.