Despite assurances from the BBC that sound levels had been adjusted for the second episode of new drama Jamaica Inn, a further 252 people complained following last night's episode.
Almost 800 viewers have now complained about the TV adaptation of Daphne du Maurier's classic gothic novel, with people saying they had to switch on subtitles and turn up the volume to maximum to understand what was being said.
The programme, starring Downton Abbey actress Jessica Brown Findlay, initially pulled in 6.1 million viewers but has since lost 1.6 million.
Emma Frost, who wrote the screenplay, suggested that a technical fault, rather than the way that the cast delivered the lines, was to blame.
"No surprises here - I'm told there was a major sound problem for tonight's broadcast of Jamaica Inn - not surprised you couldn't hear it," she wrote.
The drama, set in 1821 against the windswept Cornish moors, was directed by Philippa Lowthorpe, whose credits include Call The Midwife.
The three-part series follows Mary Yellan who is forced to live with her aunt and domineering uncle following the death of her mother.