While the term high-fidelity has been around for decades, high-definition audio is a relative newcomer to the scene. The technology company Intel has led the way to defining a set of specifications and hardware for digital sound on computers that they call HD Audio. Unlike hi-fi systems, which can incorporate both analog and digital signals, high-definition audio focuses solely on digital media. It lets your computer act like an audio receiver and amplifier.
The Intel high-definition audio chip allows you to use your computer to send digital audio signals to speakers, headphones, telephones and other audio equipment. Early computer audio systems could only produce simple stereo sound reproduction. The Intel HD audio system supports surround sound up to Dolby 7.1 [source: Intel].
The main focus of the product is to create an immersive experience. Through the use of surround sound, it's possible to create an audio environment in which you're in the center of a performance. That doesn't mean the sound will be an accurate representation of the original recording conditions. Intel's HD Audio system doesn't include outputs like speakers or headphones -- you have to supply those yourself. If you hook up lower end output devices to your computer, the sound you'll hear might not replicate the original performance accurately.
In other words, an inexpensive surround sound theater system might immerse you in the listening experience, but it won't achieve the goal so many audiophiles chase after. But for many home theater applications, such a system would be fine. Even if the system didn't recreate sound to the exacting standards of an audiophile, it could still create an immersive experience as part of a home theater system.
There you have it. A high-fidelity sound system meets subjective standards and reproduces sound accurately. A high-definition audio system supports the latest digital audio formats and creates an immersive experience. The two are related, but aren't interchangeable. It's possible to create a high-fidelity system that doesn't rely on digital media at all, for example. When in doubt, if someone asks you if you'd like to listen to a hi-fi or hi-def sound system, just say "sounds good to me!"
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