One of the most common complaints to BBC television in recent years has been that some people find it hard to hear the dialogue in our shows.
They cite many reasons for this, the most common among them being background music being too loud.
As a result of these complaints in 2009, Jay Hunt (my predecessor as controller of BBC One) launched an extensive study into why people were experiencing these difficulties.
BBC Vision's Audibility project was a huge undertaking. It involved using our 20,000-strong panel of TV viewers across the age, geographical and social demographic and a good deal of technical experimentation.
This included an engineering analysis of programmes, remixing soundtracks on clips and much more.
We also worked with the Voice Of The Listener And Viewer, Channel 4 and the Royal National Institute For Deaf People to find out once and for all what it is that can make it hard for viewers to hear the dialogue in our programmes properly.
The results were surprising. It turns out that audibility is not just about background music, as many had thought.
In fact issues range from clarity of speech - namely mumbling, muttering and muffled voices - to unfamiliar accents. Background noise such as traffic was also an issue.
However what we discovered was that it was a combination of factors could really create problems - for example a mumbling actor, recorded in a noisy environment with added music.
What struck me is that many of the problems could be resolved long before a single frame is shot if more emphasis was placed on planning for clear sound.
For example, has the director chosen the right location and what are the implications for getting good sound? Has the person looking after sound had training and the right level of experience? Are the presenters briefed to recap if they feel key messages are not clear?
If a contributor may be difficult to understand, can they be in vision as much as possible so viewers can see their lips move?
In testing, when we remixed sound tracks on video clips; with the music taken down a notch the results were fascinating.
Reducing the music by just one point, four decibels, when the programme is finally mixed allowed many more people to understand what was being said without compromising the editorial vision.
This was particularly true for people who had any form of hearing loss.
One invaluable piece of information I've learned along the way is that age-related hearing loss can begin as early as in our 40s. Many of us are completely unaware that our hearing could be deteriorating and think the issue is with TV programmes.
But for me, this is something we need to be aware of - particularly those making programmes for mainstream channels like BBC One.
The result of this research is that we now have a 'best practice' guide for programme makers available on the BBC Academy's College of Production website.
This gives clear guidance on the small things that programme makers can do to make a big difference to the audience's ability to hear and therefore enjoy our programmes to the fullest possible extent.
My thanks to all our partners involved in this project. It has been a fascinating and very useful study.
Danny Cohen is controller of BBC One.
Further guidance has now been published on the BBC's Editorial Guidelines website.