How we test: MP3 players
MP3 players come in all shapes and sizes. Some are loaded with every possible feature except the kitchen sink, while others contain large-capacity hard drives seemingly capable of holding more music than is stored in the vaults of the Library of Congress. Diversity is the spice of life, but it also means that no two models of MP3 players are the same. Our rigorous testing is designed to provide a complete appraisal of the features and functionality of MP3 players by examining usability (ease of use, menu navigation, durability, and so on), sound quality (both subjective and comparative appraisals), and battery life.Usability
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We put each MP3 player though its paces for a minimum of 10 hours, evaluating menu navigation, song navigation, durability, ease of use, control layout, display readability, shuffle/playlist functionality, ease of installation, stylishness, software interface design, and ergonomics. We access all available features a number of times so as to gauge a player's performance relative to other devices. Usability tests are conducted in CNET Labs and outside the office in various real-world situations, such as while riding a bicycle, walking down the street, or working out at the gym.
Sound quality
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We check a player's manufacturer-supplied specifications for
signal-to-noise ratio, total harmonic distortion, and noise, frequency
response, cross-talk and milliwatt power output (at 30 ohms of resistance)
using an Audio Precision ATS-2 Audio
Analyzer. We then compare the specs against our own experience with
the player, in order to judge the audio signal's cleanliness, fidelity,
volume range, and bass and treble response. We use a random selection of
MP3 files as well as a set collection of songs from various genres in both
MP3 and WMA formats (or AAC in the case of Apple iPods). If the player has an FM tuner, we listen to the
same radio stations at the same location in order to see how strong and
clean the reception is.
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We appraise a player's sound quality using the included headphones as well as our reference headphones, which include the sound-isolating Shure SE310 earphones and the full-size Ultrasone HFI-700 headphones. Initial listening tests are performed with no EQ engaged or with the EQ set to flat to get a sense of the sound quality in its cleanest state, without the benefits of enhancements. (Audio performance rating is based primarily on this initial test.) Tests are repeated using the various manual and automatic EQ settings to get a sense of their effectiveness. We test voice, line-in, and FM-recording qualities if those features are also available.
