El, interesting point. If we look at a 20K waveform, one cycle of the wave is only sampled twice in redbook cd encoding. The entire cycle of the waveform must be reconstructed from only these two samples.
Editor John Atkinson makes some interesting points in his review of the Meridian CD player in the latest Stereophile. He correctly points out that if one looks at the impulse response of CD players, one can see ripple both before, and after, the impulse. This being a consequence of the use of FIR filters. It was thought that this ripple was of very minimal importance, as it is both down in level and at the Nyquist frequency of 22.05K. However, the work of Peter Craven seems to indicate that, while the post impulse ripple is covered by natural decay and becomes part of the music, the distortion that precedes the impulse is not masked and is psychoacoustically destructive. He goes on to posit that this is not related to our regular frequency dependent perceptions, but that humans also have a type of wavefront detection mechanism that is independent of our freqency perception. The pre ripple trips this wavefront detector and is perceived as diminishing the detail in the music. Now, this is intrigueing as it makes sense in the context of us living in caves and huddling around the fire, but there are many questions that are unanswered in the brief write up. Such as, are these high frequency wavefronts perceived by the auditory system or the skin, or some other organ? Is the music diminished because some of the finite processing power of the brain is taken up in the wavefront perception process, etc? There are two AES white papers on the phenomenon, but I have not had a chance to read them yet. It does seem like an interesting idea, forwarded by scientists that are at the forefront of digital theory, rather than analog loving detractors.
Editor John Atkinson makes some interesting points in his review of the Meridian CD player in the latest Stereophile. He correctly points out that if one looks at the impulse response of CD players, one can see ripple both before, and after, the impulse. This being a consequence of the use of FIR filters. It was thought that this ripple was of very minimal importance, as it is both down in level and at the Nyquist frequency of 22.05K. However, the work of Peter Craven seems to indicate that, while the post impulse ripple is covered by natural decay and becomes part of the music, the distortion that precedes the impulse is not masked and is psychoacoustically destructive. He goes on to posit that this is not related to our regular frequency dependent perceptions, but that humans also have a type of wavefront detection mechanism that is independent of our freqency perception. The pre ripple trips this wavefront detector and is perceived as diminishing the detail in the music. Now, this is intrigueing as it makes sense in the context of us living in caves and huddling around the fire, but there are many questions that are unanswered in the brief write up. Such as, are these high frequency wavefronts perceived by the auditory system or the skin, or some other organ? Is the music diminished because some of the finite processing power of the brain is taken up in the wavefront perception process, etc? There are two AES white papers on the phenomenon, but I have not had a chance to read them yet. It does seem like an interesting idea, forwarded by scientists that are at the forefront of digital theory, rather than analog loving detractors.