Description of Dolby Headphones
DirectDVD 5.0+ Versions
Compiled 4-5-03
A Listener's Guide to
Dolby Headphone Technology
Dolby Headphone technology is a unique signal-processing system that enables your stereo headphones to portray the sound of a five-speaker, surround-sound playback system.
With Dolby Headphone technology, sound that is supposed to be in front of you is in front of you. Sound that is supposed to be all around you is all around you. It no longer sounds like it's all happening inside your head.
Dolby Headphone technology lets you enjoy multichannel sound sources, such as Dolby Digital and Dolby Surround movies, with thrilling, realistic surround sound over any conventional stereo headset. You also get far more natural sound on stereo sources, from CDs to MP3 files. And on any kind of program, you'll be able to listen longer, with far less listener fatigue.
Dolby Headphone technology can be incorporated into virtually any type of product—audio, video, PC, or video game—normally featuring a headphone output, and is identified by the Dolby Headphone symbol.
Speakers versus Headphones
As the sound from each speaker in a stereo system reaches your inner ears, it acquires a set of spatial cues imparted both by the acoustics of the room and the physical properties of your head and outer ears. These cues enable the brain to localize the sounds and integrate them into a soundfield that appears to array the performers in front of you as they would be at a concert (see Figure 1).
figure 1
Headphones, on the other hand, feed the sound directly to your eardrums, devoid of any of the spatial cues imparted by playback over speakers. The result is an unnaturally wide image forming a straight line between your ears (as in Figure 2).
figure 2
Left and right sounds appear directly beside you, while center sounds appear within your head. The overall result is unrealistic, and can cause listener fatigue.
It's difficult enough to portray two-channel stereo convincingly via headphones—but surround sound, which uses five speakers to reproduce the programs, is even more of a challenge. Multispeaker home theater systems not only array primary sounds in front of you like a stereo system, but also immerse you in the ambient sounds that impart the thrilling sense of "being there" to movies and TV shows (see Figure 3).
figure 3
How Dolby Headphone Technology Works
When you listen to your stereo or home theater system, your ears receive both direct sound from each speaker and multiple reflections contributed by the room's surfaces and furnishings (as shown in Figure 4).
figure 4
The combination of direct and reflected sound is unique for each speaker in the system, depending upon both its location and yours.
By the time it reaches your ears, the sound from each speaker has acquired a unique signature. Taken together, these signatures cue your brain as to the size and acoustical properties of the room, the speakers' locations, and the spatial properties of the original sound.
Using powerful digital signal processing technology, Dolby Headphone technology electronically imparts to each audio channel—two on stereo programs and up to five on surround programs*—the sonic signature of a corresponding speaker properly placed in a carefully defined acoustic environment. In other words, Dolby Headphone technology creates up to five virtual loudspeakers in a virtual room.
The processor combines all this information into two encoded channels that deliver to each of your ears, via conventional stereo headphones, a unique sum of direct and reflected sound from each virtual speaker (see Figure 5). As a result, the listening sensation is much more natural, with sounds appearing "out-of-head."
figure 5
Up to Three "Listening Rooms"
Because of the way it works and the power of its signal processing, Dolby Headphone technology can model the sound of a playback system in up to three different listening environments, based on acoustic measurements of real rooms:
DH1 is a small, well-damped room appropriate for both movies and music-only recordings. It is the Dolby Headphone "Reference Room" and is provided on all Dolby Headphone technology equipped products.
DH2 is a more acoustically live (or "wet") room particularly suited to music listening, but also great for movies.
DH3 is a larger room, more like a concert hall or movie theater.
Only one or two of these room options may be provided by some products equipped with Dolby Headphone technology. On those offering a choice, you can easily switch between them and select whichever one suits the particular program material and your own preferences.
Other Benefits
Dolby Headphone technology works well for all listeners. No customization or user adjustments are needed.
As with speakers, basic audio quality improves with headphone quality. But even inexpensive headphones can provide excellent Dolby Headphone imaging.
Conventional headphone listening can be fatiguing, because of coloration, unnatural imaging, and other artifacts. In contrast, Dolby Headphone technology's natural externalization of sound and minimal sonic coloration make long listening sessions much more enjoyable.
You always have the "best seat in the house," because what you hear is independent of variables such as actual room acoustics, speaker placement, and listening position.
Dolby Headphone Technology Availability
Dolby Headphone technology works with any stereo program source, from CDs to MP3 files, and with any multichannel program source, whether Dolby Surround, Dolby Digital, PCM, MLP Lossless, or MPEG encoded. It can be included in almost any product that normally provides a stereo headphone jack, such as PCs and laptops; DVD-Video and DVD-Audio players; MP3 players; game consoles, portable stereos; conventional and digital TV receivers; home theater surround decoders and receivers; digital cable and satellite set-top boxes; VCRs; auto entertainment systems; and multimedia speaker systems. It's also available as part of DVD playback software for computers, and is used for in-flight entertainment programs on several airlines.
Multichannel products that incorporate Dolby Headphone technology to emulate multispeaker surround playback, such as those with Dolby Digital 5.1-channel and/or Dolby Surround Pro Logic or Pro Logic II decoding, display the Dolby Headphone symbol. These products also apply the Dolby Headphone process to stereo programs. Stereo equipment that provides Dolby Headphone technology to emulate only the two-speaker listening experience is identified with the Dolby Headphone Stereo symbol.
Just plug in your favorite stereo headphones, sit back, and enjoy the best seat in the house.
