BBC TV chief Charlotte Moore has promised to tackle problems with sound on hit dramas such as Happy Valley but admitted it is often “incredibly hard” to identify what goes wrong.
Viewers complained they could not hear the dialogue in the latest series of the Sarah Lancashire drama, which was watched by more than eight million people.
Two years ago another BBC1 drama, Jamaica Inn, generated more than 2,000 complaints about muffled conversations.
Moore said the BBC had issued a new set of guidelines to programme makers to attempt to prevent a repeat.
“Sound has been a big issue – all of us want to make sure that sound levels are absolutely so people can hear the fantastic work we are doing,” Moore said.
She said producers had gone back into the edit suite following complaints about the first episode of Happy Valley to solve the issue.
“After episode one we took everyone back into the edit to really try to make sure, to work very hard to make it crisper and change those levels, Moore added.
“It is something we take incredibly seriously.
“It is incredibly hard to get to the bottom of where things go wrong. “It’s often several circumstances and it’s quite hard to isolate if there is one particular problem.
“It is often several different problems coming together. Sound is a very exact science.”
Moore said she was currently pulling together all the available advice to help programme makers to do “all those final checks” to make sure there were no problems with sound.
“Getting to the bottom [of this] is usually a bringing together of several issues, and that is what we are working on with suppliers to make sure these things don’t happen again.
“We know how difficult it is – there are multiple reasons.
“We have had a couple of instances of issues where people have felt very strongly.
“We went straight into the edit to see what we could do. Of course none of us want our drama not to be heard.
“The will is there from all of us.”
Poor sound quality has also been blamed on the new generation of flat TVs, which have less room for speakers than traditional TV sets.
In 2009, then BBC1 controller Jay Hunt launched an “audibility project” involving a 20,000 strong panel of viewers and listeners.
The initiative followed complaints about a string of BBC programmes and led to a “best practice” guide for programme makers, not all of which appears to have been heeded.
Happy Valley is set in the Calder Valley in West Yorkshire and was made by Salford-based Red Production Company for the BBC.
Post production was done by Dock 10 at MediaCity.