DTV Still Plagued by Hearing Problems

Digital television sound, based on Dolby Digital, is delivering TV sound with the promised CD quality, providing a rich, new aural dimension for consumers seeking the theater-like experience in their homes. But the standard continues to be plagued by loudness spikes and, what's worse, lip sync troubles. Engineers throughout the TV production and distribution food chain are working on remedies. Dolby believes some of them lie in better education and closer adherence to the protocols for using the system. The Dolby system has built-in loudness normalization parameters that producers can set with metadata so that decoders, be they high-end audio systems, digital TVs, Dolby-standard digital cable set-top boxes or even older analog TVs, recognize and adjust sound to proper levels. According to Hunold, all Dolby signals, regardless of their source and regardless of how loud they are, are controlled by the parameters. Ideally, he says, this means that one channel would sound the same as another and sound within a channel would not spike or drop. But it's up to the program producers to set those parameters, he says. Dolby is also working with cable companies and broadcasters to help them understand the different parameters.