Quote:
Originally Posted by 24-96 Mastering  However, I'm also interested in the theoretical, generic claim made in the original post: That in any (non-dithered) PCM recording system, sampling rate supposedly has an influence on SNR. First, I don't understand how that is possible because a generic undithered PCM system has no noise floor. |
Robin, I believe that the original quote by Bob Katz is made about a dithered PCM system, however it still holds true for a non-dithered PCM system. When quantizing a signal at a higher sampling rate, the quantization distortion (or dithering noise) has the same power (defined by the amplitude of the least-significant bit), but their spectrum is spread over a wider frequency range. If we are only interested in noise (or distortion) levels in the limited audible range, their levels (and power spectrum density) drop when higher sampling rate is used.
I believe that both
Dan Lavry and
oky**** are correct and there's nothing to argue about.
Dan's argument holds true when the dominant noise in the system is an analog noise (e.g. when recording at 24 bits). In this case, doubling the sampling rate captures a wider range of analog noise. Since analog noise is typically white, this doubles the power (+3 dB) of the recorded noise. However the noise level in the audible band remains the same.
Oky****'s (and Bob's) argument holds true when the dominant noise in the system is quantization or dithering noise (e.g. when recording at 16 bits). In this case, analog noise has relatively little impact on the recording, and quantization (or dithering) noise is spread over a wider frequency range, which results in decreased noise levels in the audible band.
Another related observation is that with many noise-shaped sigma-delta A/D converters full-band noise levels dramatically rise with higher sampling rates because noise shaping curves are only crafted to remove noise below 20-40 kHz, while high sampling rates reveal much of the ultrasound noise that is "shaped out" of the audible band.