OK, folks, here you go. By popular demand, it's narkspud's audio guide to HD artifacts.
I'll warn you again, if you are happy with your HD radio, just skip this post and pretend you never saw it. Once this sound gets in your ears, you will not be able to listen to your lower-bitrate HD stations anymore, because it will drive you bananas.
Still with me? OK. Here are 4 actual, hot-off-the-press airchecks from Hollywood, USA. I hope my ISP doesn't demand my head on a pike after I do this . . .http://members.dslextreme.com/users/narkspud/KSCA-2.mp3
This sample really shows off The Artifact. Notice the raspy fizz that accompanies the vocals. That's the sound. If you're a vinyl guy it makes you want to wipe the big gob of lint off your needle. It's most obvious on the vocals here, but it's affecting everything. I'm assuming this is a 32 kbps stream, because this is pretty heinous.http://members.dslextreme.com/users/narkspud/KMVN-2.mp3
A male vocal with exactly the same Artifact, on a different station's -2. He's a raspy-voiced dude, but the artifact isn't rasp . . . it's a consistent hiss that pops in whenever the high-frequency energy passes a certain frequency and intensity. This sample's really short, but listen to the word wallowed at :03, where the o turns into this weird buzzy tone that doesn't even sound human, and how a swish of fizz pops in as the w goes to the e in the word welcome at :07. I think that's the main thing that bothers me so much about the HD Artifact . . . that it comes and goes second-by-second, depending on what's going on in the program material. If it was steady, I could ignore it. If it was higher pitched, I could EQ it out. Here, it's too far down into the business frequencies. I'm stuck with it hissing at me.http://members.dslextreme.com/users/narkspud/KOST-1.mp3
Now that you have it in your ear and are doomed to hear it in everything from now on, here's a somewhat longer and better-sounding sample. The fizz is still there, but in a higher register, and not as noticeable. It comes out as a kind of artificial sheen on the vocals rather than an obvious foreign sound, and a harshness in the strings at :23. When Linda sings see at :20, that's the worst spot, and, not coincidentally, the highest note they sing. Listen also to the hi-hat cymbals, which are hissing rather than making proper metal cymbal sounds. KOST's super-squash level limiting isn't helping either, but that's not the source of the fizz, just a contributing factor to its intensity. This is what most of the multicasting stations sounded like to me. Yes, sounded. More on that in a sec.http://members.dslextreme.com/users/narkspud/KKGO-3.mp3
FM HD Radio's near-CD-quality sound from my buddies at KKGO. Mono AND fuzzy. The worst of both worlds. I can't imagine trying to listen to this. As noted earlier, I'm not sure I can blame this on HD - I can't believe even a 32 kbps mono stream would sound this bad. Their primary stream, which is country, sounds exactly like this, only in stereo. (Note: I was typing this at the same time as k6sti was typing his comments above. I'll reply in a moment.)
I will tell you that, now that my Sangean HDT-1 is back, I have noticed either a big improvement in the sound of some of the FM's primary streams, or else I'm finally starting to get used to that sound, just a little. If I had to place a bet, I'd say that several of the locals have decided that 64/32 is preferable to 48/48 (since I also don't remember KSCA and KMVN's secondaries sounding as bad as the samples above). If you think it's improved processing or a codec upgrade, I ain't gonna argue with you.
I also noticed a couple of stations that seemed to be rolling off their highs to reduce artifacts. KIIS-FM2 was one of em. It does seem to help a bit.
And a reminder . . . I'm the guy who thinks 96 kbps sounds great, so please don't spraypaint a big orange HD logo on my car while I'm asleep.