The first episode of the long-awaited second series was trending on Twitter last week, with people referring to “mumbling” and inaudible dialogue.
But the BBC has defended the show, saying the soundtrack is “representative of the characters and area in which it is based”.
The show, filmed in and around the Calder Valley, stars Sarah Lancashire as troubled police officer Catherine Cawood.
Twitter user Mario Fretti wrote: “Again a good show is spoilt by the sound, too much whispering and mumbling.”
Another Tweeter called Kez wrote: “Stayed up to watch Happy Valley after a night out. So glad it’s back but had to turn volume right up to decipher mumbling.”
Today the BBC responded: “We worked very hard to ensure everything was audible while keeping the sense of reality and the rawness of performances.
“Happy Valley is a drama that has been lauded for its realism and dramatic pathos – as such the dialogue is representative of the characters and area in which it is based.
“We trust it didn’t interfere with the audience enjoyment of the opening episode which was watched by 6.5 million.”
It is not the first time a BBC show has faced criticism of this nature - nor the first time the corporation has laid the blame on the shoulders of a regional accent. In 2014 as hundreds of people complained about the sound in the West Country drama Jamaica Inn.