Strangely, watching a great programme on digital TV can boost the ratings for a rotten programme, warns Nielsen Media Research. Several channels are transmitted in the same bundle of digital frequencies, known as a multiplex, so ratings systems that just log the frequency the TV set is receiving will not know which channel is being watched (US 2004/0181799).
Nielsen’s new set-top ratings measurement box uses a microphone to monitor the sound coming from the TV. The sound is compared with all the soundtracks being transmitted at the time until one of them matches the programme.
