Dolby® Virtual Speaker produces a surround sound experience over stereo speakers, creating a virtual 5.1 speaker system without the extra speakers, cost, wires or hassle. This proprietary technology processes encoded multi-channel soundtracks, rewriting and re-encoding them for output over two speakers without losing the surround sound effect. Seem impossible? Not to the creative folks at Dolby.
To understand how it works, consider a simple sonic signature. A speaker is placed several feet (2-3m) in front of a subject in a typical-sized living room. A tone is emitted from the speaker. Some of the sound waves reach the left and right ears directly at slightly different intervals, but other waves bounce off walls, ceiling and flooring, reaching the ears not only at different intervals but also at slightly different levels of volume and tone. The brain calculates both direct and reflected sound to pinpoint the signal source and to gain a feel for the size of the room.
By processing sounds to arrive at different intervals, to fluctuate in tone, level, and in other subtle qualities, the ears and brain can be “tricked” into thinking sound is coming from further away than it is, or from a certain direction — even from behind.
To accomplish this, Dolby Virtual Speaker utilizes sound canceling technology or crosstalk cancellation to maintain strict control over what each ear hears. Sound waves that would spoil the effect or give away the true source of the signal are eliminated from the sound spectrum by each speaker issuing not only its part of the soundtrack, but also mirror images of the opposite speakers output. This prevents the right ear from hearing things it shouldn’t from the left speaker, and visa versa. In this way Dolby Virtual Speaker can create the illusion of precisely placing sound wherever it wants, replicating a 5.1 surround sound experience.
Dolby Virtual Speaker resides on a chip that can be built into an entertainment receiver, PC, television, boom box, or any audio device that has speaker outputs. A receiver might be capable of 5.1 output using several speakers, or Dolby Virtual Speaker output using just two. Everyone wants the benefit of surround sound, whether gaming, watching TV or viewing a movie. Now everyone can have it, regardless of physical space, budget or other constraints that might make a surround sound system impractical.
While checking out your next PC, DVD player, or receiver for Dolby Virtual Speaker, watch for Dolby Headphone technology as well. It sends virtual surround sound through your headphone jack, turning any pair of stereo headphones into surround sound headphones. Dolby's website has audio demonstrations of both technologies.