SRS.PDF

3D S TEREO S OUND TM

WHAT IS SRS?

SRS Labs, Inc. develops, markets and licenses unique, leading-edge audio technologies for use in

the consumer electronics, computer multimedia, electronic game, automotive and professional

sound industries. The company’s flagship technology, SRS, the Sound Retrieval System®, replaces

stereo as the method of accurately reproducing sound and is rapidly becoming the standard for

3-D audio technology. It creates a three-dimensional sound image from any audio source with

only two conventional stereo speakers. Whether the signal is mono, stereo, or surround sound

encoded, SRS expands the audio material and immerses the listener in an exciting three-dimen-

sional sound field. This unique process has been awarded four U.S. patents with 260 claims and

20 issued foreign patents, with 50 pending patents in countries around the world.

SRS, the Sound Retrieval System, was invented by Arnold Klayman after years of research on the

psychoacoustics of sound and the dynamics of the human hearing system. SRS differs from stereo

and traditional sound expansion techniques because it is based on the human hearing system. It

retrieves the spatial information from recordings and restores the original three-dimensional

sound field. As a result, the reproduced sound is much closer to a live performance. Like live per-

formances, SRS has no critical listening position (sweet spot). Listeners can move around the

room and continue to be immersed in full three-dimensional sound. Speakers are no longer the

discernible source of sound. SRS does not require special encoding or decoding, and does not rely

on artificial time delay or phase manipulation of the original program material.

WHY IS SRS NEEDED?

The SRS technology is based on the characteristics of the human hearing system. To understand

SRS, you must understand a few of the components of sound and how your ears and brain use

them to construct three-dimensional audio images.

If you rub your fingers together in front of your forehead and then slowly bring your hand around

to the side of your head just out from your ear keeping the same distance between your fingers

and your head, you will note a slight rise in volume and more emphasis on certain mid and high

frequencies. In this experiment, rubbing your fingers serves as a stable volume and frequency

sound source. Your ears will hear and register to your brain the identical sound very differently,

depending on whether the sound comes from in front of you or from the sides. The side sound is

much louder and higher in pitch because of your pinna-the external, fleshy portion of your ear.

When the sound wave arrives from the front of your head, the pinna will reflect many frequency

components away from the ear canal. Side sounds that enter the ear canal are not reflected by the

pinna as much as frontal sounds, so the intensity and the arrival time of the side sounds are differ-

ent from the frontal sounds. The ear then transfers all of this information to the brain. These

spatial cues supplied by the pinna to your brain are called HRTFs or Head-Related Transfer

Functions. Because they depend on the volume and direction of the sound, the transfer functions

of the sound waves from the pinna and ear canal are constantly changing. They change because

the sounds they register constantly change. This transferred information gives your brain the nec-

essary details to understand what you are hearing and from which direction you are hearing it.

Because a microphone does not have a pinna, recordings made with microphones will always misin-

terpret the proper frequency representation of side sounds, regardless of how many microphones are

used. The original ambience and dynamic feeling of live sound are therefore masked or lost. SRS

takes into account the constantly changing transfer functions of the human hearing system and

restores the proper frequencies and proportions of direct and indirect sound waves so that what the

listener hears is closer to the original performance.

HOW DOES SRS WORK?

As mentioned above, a microphone does not possess the ability to interpret the direction a sound is

coming from in the same way that the human ear does. Traditional stereo reproduces a flat, two-

dimensional sound field. However, when the audio source is recorded, directional audio cues are still

present in the recording. These cues such as ambient or reverberant sounds are simply masked in tra-

ditional stereo playback.

By breaking down the stereo signal into its various signal components, it is possible to isolate and

restore these spatial cues, which include ambient sounds, such as crowd noise at a ballgame. SRS tech-

nology extracts this information and processes it through a patented frequency response correction

curve. This curve restores the appropriate location of the ambient sounds relative to the direct

sounds, such as a soloist or dialogue.

Stereo has a narrow sweet spot

SRS 3D Sound expands the stereo sweet spot

By isolating then enhancing these spatial cues, several things occur: the stereo image is enhanced by

restoring the ambience of the live performance thus creating a much wider listening area. You can

walk about the room and still retain a sense of direction of all the musical instruments. The “sweet

spot” disappears and you no longer have to sit precisely between two loudspeakers. Audio realism is

restored.

For marketing and PR information on SRS

technology and the SRS Labs licensing pro-

gram, contact:

Jennifer Drescher

Director of Marketing Services

email: jenniferd@srslabs.com

SRS Labs, Inc.

2909 Daimler Street

Santa Ana, CA 92705

http://www.srslabs.com

1-800-2HEAR3D/1-800-243-2733

Phone 714.442.1070 • FAX 714.8521099

Retrieval System and the phrase “everything else is only

stereo” are registered trademarks of SRS Labs, Inc.

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