Last month HDNet completed the installation of its third “listening room,” a studio created especially for the review of sound on the network’s programs to ensure the audio feed the network delivers along with its high-definition picture is top-notch.

Sound often takes a back seat to video because TV is a visual medium. But with the number of hi-def sets homes growing, sound is becoming more important. According to Leichtman Research Group, about 21.5 households have an HD-capable TV set today, up from about 13.5 million a year ago.

The network’s investment—the rooms cost $20,000 to $100,000 for HDNet—illustrates that sound, the lower-profile element of the audio/_visual experience of TV, is particularly important for networks that live and die in hi-def, because they want the aural output to match the visual majesty that the higher-resolution format provides. “You’ve got to be in a room to hear how it sounds,” said Philip Garvin, co-founder and general manager of HDNet.

The HDNet listening rooms are outfitted with front and rear speakers to mimic a surround-sound home. “You want to know are you listening to it the way it’s supposed to be listened to in the home …. When a program gets here, whether by our own staff or an acquired program, we need to make sure it sounds right in the home. There are certain programs where the surround sound is extremely important—concerts, programs heavy in special effects.”

In most cases, hi-def programmers produce the sound with hi-def shows in Dolby Digital 5.1, which has become the de facto standard for sound in the TV industry. Most prime-time shows on broadcast networks that are shot in hi-def are also produced in Dolby Digital 5.1.

What’s more, Dolby Digital technologies have been incorporated worldwide in more than 79 million set-top boxes and in more than 36 million audio/video receivers, the company said.

“We are trying to present an immersive experience where the experience is so complete that you really feel surrounded by the experience of being in the movie or the program,” said Greg Moyer, general manager of Voom HD Networks, which counts 15 hi-def channels. “We want sound coming from five or six speakers to add to the realities of watching a television movie. Any kind of high-end television experience that aspires to be more like what we consider the motion picture experience in the theater needs to think very seriously about sound.”

Most of the 15 Voom networks transmit their channels in Dolby Digital 5.1. Nearly all original programming is shot in 5.1, Mr. Moyer said. Some older movies—those shot before 5.1 became the norm in the mid ’90s —are not carried in 5.1, he explained.



Replicating True Sound

The 5.1 technology is designed to more closely replicate actual sound. “The whole game is to make it seem like there is no barrier between you actually being somewhere and experiencing the way your ears would and watching it virtually on a TV screen,” Mr. Moyer said.

In addition to transmitting most of its networks in 5.1, Voom also produces interstitials and promos in 5.1 to maintain the aural experience throughout the programming lineup. Mr. Moyer thinks that as the HD transition continues, more program producers will pay attention to sound.

HDNet has carried its entire programming lineup in 5.1 since the network launched in 2001, Mr. Garvin said. “One of the things we decided early on was we will always be 5.1,” he said. “The best comes from when you are doing original 5.1, when you shoot the program in 5.1.” However, if a program was not shot in 5.1, HDNet will synthesize the stereo feed into a 5.1 feed.

In addition to the growth in HD sets and Dolby Digital 5.1 usage, the sound technology company also is introducing Dolby Digital Plus, a new “codec” —the technology that encodes and decodes audio—for the next generation of Dolby sound technology. The new codec enables cable and satellite operators to determine the audio data transmission rates.



Bandwidth Issues

As operators grapple with how to efficiently manage bandwidth, the advanced codec is one more mechanism that gives them control—they can turn up or down the amount of bandwidth needed to transmit sound, said Page Shaper Haun, director of the broadcast business unit, consumer division, at Dolby. The sound quality remains the same for consumers.

Dolby Digital Plus hasn’t been deployed yet in the U.S. However, Ms. Haun said Dolby is in talks with its broadcast and cable partners about how to launch the new technology here. She expects rollouts will begin in the next 12 months.

She thinks satellite and IPTV companies will adopt the new codec first because they face more bandwidth challenges. That’s because as cable operators convert from analog to digital, they can reclaim bandwidth. Since satellite is already all-digital, satellite operators don’t have a new source of bandwidth, she said. As a result, most want and need to make more efficient use of the bandwidth they have.

“Sound is part of the immersive experience of HD,” Ms. Haun said. “Part of the budget goes toward the audio side.”