DAB audio sound quality
Posted on Sunday, October 8th, 2006 at 2:16pm. #
Someone discovered an old H2G2 article I must have written in the last 1990s about DAB Digital Radio… and emailed me. Here’s his email, and here’s my reply.
Dear James,It’s a pity that your article in H2G2 does not make it clear that your enthusiasm for DAB radio (at least in its UK application) relates to portable and car radios, i.e. where clear interference free reception matters far more than ultimate sound quality. For home HiFi use FM is vastly superior, not just “while their both nice but maybe that one’s a bit better” but poles apart in audio quality, particularly as you approach the audio frequencies in the range 8KHz upwards. Similarly FM is not hard to use as you say: my domestic tuner (Cyrus) and my car tuner (Kenwood) both have presets, and the display shows the name of the station playing. Reception in the car is not always interference free, though along the motorways it usually is. FM reception at home is as perfect as DAB (I also have an ARCAM DAB tuner) from a background noise and interference point of view. There is no background noise whatsoever even at high volumes, and I live in a site quite distant from the best transmitter. We have a Roberts DAB portable which is also FM capable. There isn’t much to choose in sound quality, but the DAB reception is more reliable. If the BBC and other broadcasters had not agreed the very low standard of digital radio technology as is represented by DAB things might be differerent, but the low datarates, with even Radio 3 now broadcast at 128kbits/s gives us sound quality which is at best mediocre, and for the most part very poor indeed.I do not doubt that pressure on bandwidth to allow for more and more broadcasters means that FM is dying and DAB will take over, but make no mistake, it will be the end of broadcast HiFi as we have enjoyed it for nearly 50 years. I think that the days when people actually cared about sound quality have gone to some extent. Pop music, played at the usual very high volume cannot be judged in terms of distortion of the original sound, since the original does not really exist in any meaningful way. Conversion to MP3 at 128kbits/s of course leaves it completely unaffected. Try doing that to the sound of a large choir singing Bach’s B minor mass, and you will turn it off in despair that such a technology could be foisted upon us.
Yes, a perfect FM signal, if you’re blessed with one, does a great job of radio reception, you’re right. Naturally, this assumes…
- The station you want to listen to is on FM
- You have perfect reception, with a roof antenna if possible
- You have no interference from pirates or other broadcasters
(For my own part, I listen to BBC Radio 5 Live and BBC 6 music, which aren’t on FM; and LBC 97.3 which is on FM but splattered all over by pirates).
And true, your FM receiver shows the name of the station playing, but not the name of the song playing or other useful information (unless you’ve a really unusual radio with something called RDS RadioText; and not many people support extra info on this anyway).
I think you’re missing the point slightly with the audio quality of BBC Radio 3 in a number of ways.
- First, I don’t work for them, but they’re not 128k - my understanding is that they’ve dropped from a permanent 192k to a permanent 160k (though this is dynamic and can drop to 128k for a small amount of times a day; particularly when BBC Radio 4 is doing a ‘Yesterday in Parliament’ opt-out, and Radio 5 Live Sports Extra is broadcasting). This coincides with much more efficient audio encoding techniques - which should mean BBC Radio 3 at 160k sounds better or similar to Classic FM at 192k, which is using much older encoders. The bitrate number isn’t the only thing.
- Second, nobody’s taking FM away from you. No date has been fixed, and nobody is even talking about switching FM off. If you’re blessed with that perfect FM signal, you can keep on listening to it.
- Third, you also have the choice, particularly in a perfect audio environment like your front room, of getting a solid and high bitrate signal from Sky Digital and from Freeview. DAB is not going to replace these either; and particularly Sky has the capacity to be much richer in terms of audio bandwidth.
You say…
“If the BBC and other broadcasters had not agreed the very low standard of digital radio technology as is represented by DAB things might be differerent”
I’m terribly sorry to disillusion you, but it wasn’t the BBC and other broadcasters - it was consumers like you that made this choice. When DAB was all 192k streams or above, and offered exemplary audio quality, nobody bought DAB Digital Radios, since they didn’t offer anything particularly extra. Now that DAB Digital Radio offers a vast extra amount of choice (doubling or even trebling the amount of stations you can get), the receivers are flying off the shelves. The truth is that most people listen to the radio in mono and don’t give a tinker’s cuss about audio quality. And the good news, for you, is that there’s plenty of other places to get fantastic quality broadcasts.
It might interest you to know that most listeners are entirely happy with the audio quality for AM music radio. Which came as much of a surprise to me as it doubtless does to anyone else!
M Green said at April 13th, 2007 at 12:00pm 
