In recent years we've seen the advent of two new forms of digital radio - satellite radio and HD radio.

What is the audio quality of these two formats? What bitrate are they - what kind of dynamic range, frequency response, distortion, etc, do they offer? How do they compare with the MP3 and AAC files we're used to - what would they be most similar to? How do they compare with each other? Do they come in different flavours or degrees of quality?

Thanks in advance.

I believe we've discussed DAB radio here before. As far as I know, DAB uses MP2 with bitrates usually between 128 kbps and 192 kbps. In other words: rubbish.

Values for the UK radio stations can be found here:

http://www.digitalradiotech.co.uk/dab/digi...o_bit_rates.htm

And what about satellite?

Also if I listen to the "HD" stream of a station on the Internet what format am I likely to hear? For example WGBH in Boston has a classical stream on the Internet at 128K. Last night I was listening to it on the little player built into their website it said 128K, but I don't know 128K-what. nAnyway, it sounded pretty good most of the time except every so often there was the most god-awful distortion that sounded like really bad clipping.

My link contains values for satellite, as well as DAB and Freeview.

If you are actually in the US then this may not be of interest.

Perhaps this thread could be relevant as well:
UK DAB digital radio sinks to a new low, 32kbps mp2 for R5 live SX, 160kbps for "flagship" Radio 3

They appear to have a flash player on their web site so it is very very likely to be just mp3.

I'm in the US and by "satellite" I meant Sirius and XM.

Is HA mostly a UK website? Typical American - I just assume everyone has a US-centric view of things!

Where do you come from?, Just wondering...

60% Europe
25% US

At least the people who responded to the poll

I don't think that there's an easy answer to this.

HD Radio bandwidth can be split to host a number of different streams/signals. The more HD channel offerings a station has, the lower the bitrate of each individual channel. Stations that offer multiple channels can also choose how to partition things -- allowing their music channel to have a higher bitrate than a talk channel, for example.

I believe that the rates on Satellite (Sirius and XM) vary as well -- music is better quality than talk offerings.

Here are a few stats for the US:

FM HD Radio uses AAC as the codec with 96 kbps availalbe for any given frequency. The radio station can divide that 96 kbps into multiple streams. For instance, many stations will simulcast their analog signal on their HD1 using 64 kbps. Then will provide a second stream (essentially a second radio station) at 32 kbps. The station engineer can divide up the streams however they like...for instance 48 and 48 kbps for two HD streams. HD Radio has provisions to divide up the signal in to 3 or more streams...but the audio quality for each stream will drop as the bitrate gets lower since the total bandwidth is just 96 kbps.

I must say that AAC sounds very good at 96 kbps. 64 kbps is still pretty darn good. 32 kbps is still very listenable, albiet with some digital artifacts.

AM HD Radio only has 32 kbps of bandwidth.

XM and Sirius refuse to release the details on their standard bitrate. Audio channels on XM are digitally compressed using the aacPlus codec from Coding Technologies for most channels, and the AMBE codec from Digital Voice Systems for some voice channels, including all of the Traffic and Weather channels. Sirius uses their own tweaked version of the PAC codec for their music channels. Bitrates are estimated to be around 32 kbps for the music channels on both services; but once again...neither satellite service will confirm the numbers.

As for dynamic range and signal to noise ratio, all of the digital services have specs similar to CD's. The actual dynamic range for HD Radio and satellite radio is squashed down by the engineers to achieve a "loud" station; and to accomodate the different levels of the various recordings. EQ of the sound is also part of the processing done by most stations.

32 kbps for MUSIC?? I don't care how good their codec is - that sounds like one sow's ear that's never gonna graduate to a silk purse. What does it sound like with good speakers?

How does it sound? Well....

I have XM plugin for foobar in my home monster rig. I go from the PC out via an audigy PCMCIA card (44.1 bit for bit) via optical to an old Audio Alchemy jitter reducer and then to my Accuphase DP-67 CD player (has digital ins to use as a processor) then to my pair of VTL Deluxe 300 amps then to Magnepan 20 speakers - MIT cabling. This is a high-res audiophile system by most definitions. So.....

XM sounds like crap. Even in my car it is not so hot. For the car it beats Philly radio by a mile simply because of the content choice of XM but the quality is just OK for the car. For the car, most pop stations don't sound good anyway so it is a bit of a toss up although XM seems more compressed with less stereo spread. On my home rig, it doesn't sound good at all so I don't use it very much. My home system is so revealing that I get annoyed if I really listen to it. OK for background music.

If I were to do it again, I would look at Sirius as I've heard it sounds better but I can't confirm it. I do like XM because of the content and the bad Philly radio.

When the two services started operation, it was rumored that the actual bitrate was somewhere between 48 and 64 kbps. But XM and Sirius got in to a "numbers" war, trading quality for quantity, as they both kept adding channels. Each service only has so much bandwidth available to them...so to add more channels means decreasing the bitrate of all the current channels to make room.

If you go to XM Fan, you will find a thread regarding the lack of sound quality that is several hundred posts long. In my opinion, when the two services first started, the sound quality was definitely better than regular analog FM Stereo. But now, the stereo seperation seems almost mono at times, and the overall sound is very compressed sounding with loads of digital artifacts.

As Bruce in Philly said, XM and Sirius are really only good for background listening. The better your stereo system, the more glaring the crappiness of each services sound quality. It's too bad because some of the content is really great. But I dumped both of my subscriptions over a year ago. Now I only hear it at a friend's house...and it still sounds like SH**.