The Clean Audio Project: Digital TV as assistive technology

Abstract

Technology used in Digital TV has the potential to enhance the viewing experience for millions of hard of hearing people. The Clean Audio project commissioned by the Independent Television Commission (ITC), and continued by Ofcom, looks at methods by which the extra information contained in 5.1 surround sound broadcasts may be used to improve the intelligibility and enjoyment of television audio for hard of hearing viewers and shows that audio processing can effectively turn a digital TV set top box into an assistive device to make digital TV more accessible. Listening tests were carried out which showed benefits in clarity and in perceived overall sound quality for hard of hearing participants by altering levels of centre and left and right channels. Further testing has shown average improvements in intelligibility of up to 9.4% by using surround sound equipment with a discrete central loudspeaker compared to stereophonic reproduction.

Preferred Levels for Background Ducking to Produce Esthetically Pleasing Audio for TV with Clear Speech

“…The right balance between foreground speech and background was shown to depend on personal taste [6,7], listener's hearing acuity [8][9][10][11], listening environment (e.g., environmental noise [12]), reproduction system [13], and listener's skill level in the content language [14].…”

Augmenting TV Viewing using Acoustically Transparent Auditory Headsets

“…More generally, our efforts in this paper were limited to using available broadcast content, utilizing center channel mixes that were not clean with respect to dialogue. However, there is a push in production toward the adoption of "Clean" [33,55] object-based audio [56] (e.g. using MPEG-H [57] or Dolby Atmos [32]), and research is being carried out examining how best to give users control over their personal mix e.g.…”

Intelligibility versus comprehension: understanding quality of accessible next-generation audio broadcast

“…DVB specifications describe 'clean audio' as audio providing improved intelligibility [37]. Two approaches to achieve this have been proposed: broadcast mix where an additional mix with lower levels of non-speech sounds is transmitted by the broadcaster [6,38] and receiver mix which generates a 'speech enhanced' mix at the set top box using signal processing [39,40].…”

“…During the transition from analogue to digital broadcasting many researchers sought to leverage the capabilities of the new formats, including the transmission of 5.1 surround sound, to achieve improved speech understanding [40]. The Clean Audio Project, funded by the ITC and then Ofcom, began in 2003 [42] and improved ratings of clarity of dialogue, sound quality and enjoyment (assessed using blind, forced choice AB comparison) by changing the mix of centre, compared to non-centre, channels for hard of hearing people.…”