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Audibility: Your levels in their hands

Volume is high on the broadcast technology agenda. First it was loudness and now it's audibility. Kevin Hilton looks at Fraunhofer's system for controlling speech and backgrounds independently and how it was used during Wimbledon.

The mild controversy earlier this year surrounding complaints about loud backing music on the BBC science documentary series Wonders of the Universe – and the annoyed response of the show’s presenter, Professor Brian Cox, to his programme being re-mixed – was made headlines on TV, radio and the mainstream press. But behind this ostensibly early silly season story is a more serious issue for broadcasters – balancing creative or subjective mixing of voice against sound effects or other backgrounds with ensuring intelligibility for all viewers and listeners, particularly those with hearing problems. This issue was also highlighted in a more objective way by a report on audibility drawn up by BBC Vision, the production division of the public broadcaster, in association with pressure group Voice of the Listener and Viewer (VLV). The BBC responded by drawing up best practice guidelines for producers, which lay out recommendations for getting the clearest sound both on location and in post-production. While this advice makes programme makers and engineers aware of the difficulty that some people at home might have in hearing what is going on, it is only a general approach and cannot address the individual problems – or tastes – of each viewer or listener. So Fraunhofer IIS has proposed a technological solution to the problem, which could put ultimate control in the living room and not the sound mixing room. The German research institute’s dialogue enhancement technology was demonstrated at the IFA consumer electronics show and IBC this year. The BBC also experimented with it during radio coverage of the Wimbledon tennis tournament. The basic concept allows TV viewers or radio listeners to increase or decrease the volume of speech against crowd noise or other backgrounds, including music. The programme soundtrack is mixed as usual for mono, stereo and 5.1 but what Fraunhofer spokesman Matthias Rose describes as “side information”, relating to the individual dialogue and effects elements, is also included in the final mix. This additional material is carried as part of a mono/stereo compatible downmix, which is transmitted as a single mix along with the parametric additional data. The side information is then decoded by specially equipped TV sets or radio receivers, which effectively produce two individual channels – dialogue or commentary and crowd atmosphere or sound effects and music. The viewer or listener can then use controls on a handset to have either more speech or more background. Rose comments that the system would be good for both the hearing impaired and people who either want the commentary on sports coverage or the dialogue in dramas to be more intelligible. He adds that TV watching football fans who prefer the sound of the crowd to the thoughts of the commentator would also find the system useful. Fraunhofer has held discussions with broadcasters, lobby organisations and standards bodies in Germany and other European countries to get feedback on what people want and how the system could be integrated into the production chain. BBC Audio and Music, which oversees the broadcaster’s radio stations and its sound output on other media platforms, had been talking to Fraunhofer about various projects and decided to experiment with dialogue enhancement during the second week of Radio 5 Live’s coverage of the Wimbledon tennis championships. BBC principal technologist Simon Tuff says that audibility has become an important issue for both audiences and the broadcaster. “At one end there is an aging population, so there are people with some kind of hearing impairment, and then there is the creative aspect, where people like Brian Cox want a cinematic production with music behind the speech,” he says. “So we’re looking at how to treat each equally and don’t compromise either the production or catering for the hearing impaired.” Tuff says the BBC chose Wimbledon for the test because the radio production workflow “could be adapted relatively easily without extra cost and planning”. Another factor was that, because the experimental transmission was over the internet, a “reasonable amount of listeners” could be expected due to the broadcasts being during working hours, when people at work could tune in online. Stereo clean feeds of the effects microphones on Centre Court and a mono clean feed of the commentary were taken to a second technical position in the broadcast area. This was done pre-fader and then fed into the Fraunhofer player and server prior to being streamed. Tuff says the intention was for the operator to ride levels on the effects and commentary as much as possible so listeners could set their preferred balance between the two and not have to change it too often, if at all. The 5 Live feed was also put alongside HDTV pictures of the games, which Tuff observes “gives a reasonable idea” of how the system would look for television. He says that adding dialogue enhancement would make productions more complicated, particularly for TV, but that the biggest challenge will be adapting domestic receivers to accept the system, although the technology is backwards compatible. Fraunhofer is in talks with manufacturers as to how this can be done but Matthias Rose is conservative in his estimate of when new systems might appear. “I don’t see any end user products in the next two to four years,” he says. Rupert Brun, head of technology at BBC Audio and Music, will give details of the BBC tests during the Radio Academy Festival in Salford on 31st October. Simon Tuff says an unexpected result was that the listeners using the dialogue enhancement system fell into two distinct groups, with approximately half of those sampled boosting the commentary and the other half increasing the effects.