Quote:
Originally Posted by ratinox
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If you have an audio CD which sounds bad, it's not because it's a CD. It's because the master used to make it was rubbish.
The Redbook audio standard is 16-bit linear PCM (pulse code modulation) with a sample rate of 44.1KHz. You can read the Redbook documents if you want the particulars. In simple terms, bit depth determines dynamic range and sample rate determines frequency response. 16 bits provides a dynamic range of 96dB, and a 44.1KHz sample rate provides frequency response of 22.05KHz. Sustained exposure to sound levels above about 80dB can cause temporary or permanent hearing loss so 96dB is more than sufficient for most recordings. Human hearing frequency range is ~20Hz to ~20KHz; a 22.05Hz high end is well above any sound any human can hear.
Put even simpler: CD audio is crystal clear. What goes in is *exactly* what comes out, with no noise or distortion introduced by the AD/DA conversions (dithering aside but dither is similar to Dolby Noise Reduction on audio tapes, replacing one kind of noise in the signal with a different noise that should be below the noise floor).
Why do some CDs have horrible noise and distortion? The masters. Back when CD audio was presented to the world, the record labels though it was going to be a short-lived fad so they spared every expense they could. They pressed CDs from third and fourth generation analog masters. What happens when you dub analog tapes? You introduce noise and distortion. What happens when you feed this noise and distortion into the audio sampler used to make CDs? You get crystal clear, flawless reproduction of every flaw in that master.
Once the labels realized that CD audio was here to stay and that they could make money from CD sales, they had their recording studios shift to digital workflows to remove as much analog noise from the process as possible. And for a time CDs really did sound great.
Then the Loudness Wars happened and put paid to that. Everything sounded flat and lifeless because it was flat and lifeless. If you take a track with say 60dB of dynamic range and compress that down to 30dB? Flat and lifeless is what you get. And if you push the ceiling too high then you get all sorts of crackling and hissing and spitting and we're back to audio CDs that sound bad.
Once the labels wised up and discovered they could make even more money they started having vintage CDs remastered so that we can buy them again.
NB: there's a tangent about oversampling but I'm not going into that here and now. Maybe later.