darmok
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- Mar 19, 2023
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I'd been under the impression that noise shaping for CD audio has been around for quite a long time and was being used pretty much universally on high dynamic range recordings. However, a quick look through my library finds very few CDs that actually show evidence of noise shaping. Sometimes I see what looks like noise shaping that's so faint that I wonder if it originated in a DSD recording that was then decimated to 44.1KHz for CD release; a lot of the time I don't see anything at all.
This is what I expect to see for noise shaping on a CD. Note how there's a significant rise in the noise floor starting at 17KHz up to 22KHz. This is evidence of the quantization noise being pushed out of the (easily) audible part of the spectrum, which results in a lower noise floor in the parts of the audible spectrum that we can more easily hear.
And this is what I see on a lot of CDs. Without noise shaping, the quantization noise is smeared evenly across the spectrum. The RMS level of this particular track is -32dB, and the peak level with the exception of the last 45 seconds is -12dB. For the first 2+ minutes the RMS level is -48dB and the peak level is -32dB! Since the noise floor of a 16-bit file without noise shaping is at best -96dBFS (and actually a little worse with triangular dither) that leaves only 48dB between the noise floor and RMS level for this stretch of the recording.
I have recordings from as recently as this year that don't seem to show any significant noise shaping. I haven't yet found a CD from before 2000 that shows visible noise shaping. Amusingly, the examples above are from the same CD which is a compilation of two recordings. The recording with noise shaping appears to have had it added after the fact, probably in the process of adjusting its level for the compilation CD. The original recording dates to 1987 and was recorded in either 14-bit or 16-bit PCM without noise shaping.
My question to everyone is: what's the earliest CD you can find that clearly has noise shaping? Can you see a pattern in when labels started using noise shaping? I definitely see it more recent releases from BIS (including the last RBCDs before they started issuing SACDs), Deutsche Grammophon, and Chandos. Naxos doesn't seem to be consistently using it, and among smaller labels I have a release on Alpha Classics from 2015 without noise shaping and one from 2018 with noise shaping.
This is what I expect to see for noise shaping on a CD. Note how there's a significant rise in the noise floor starting at 17KHz up to 22KHz. This is evidence of the quantization noise being pushed out of the (easily) audible part of the spectrum, which results in a lower noise floor in the parts of the audible spectrum that we can more easily hear.
And this is what I see on a lot of CDs. Without noise shaping, the quantization noise is smeared evenly across the spectrum. The RMS level of this particular track is -32dB, and the peak level with the exception of the last 45 seconds is -12dB. For the first 2+ minutes the RMS level is -48dB and the peak level is -32dB! Since the noise floor of a 16-bit file without noise shaping is at best -96dBFS (and actually a little worse with triangular dither) that leaves only 48dB between the noise floor and RMS level for this stretch of the recording.
I have recordings from as recently as this year that don't seem to show any significant noise shaping. I haven't yet found a CD from before 2000 that shows visible noise shaping. Amusingly, the examples above are from the same CD which is a compilation of two recordings. The recording with noise shaping appears to have had it added after the fact, probably in the process of adjusting its level for the compilation CD. The original recording dates to 1987 and was recorded in either 14-bit or 16-bit PCM without noise shaping.
My question to everyone is: what's the earliest CD you can find that clearly has noise shaping? Can you see a pattern in when labels started using noise shaping? I definitely see it more recent releases from BIS (including the last RBCDs before they started issuing SACDs), Deutsche Grammophon, and Chandos. Naxos doesn't seem to be consistently using it, and among smaller labels I have a release on Alpha Classics from 2015 without noise shaping and one from 2018 with noise shaping.