XPost: rec.audio.pro, comp.dsp   
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   On Mon, 22 Nov 2010 11:58:45 -0500, Dick Pierce   
    wrote:   
      
   >Don Pearce wrote:   
   >> On Mon, 22 Nov 2010 10:58:30 -0500, Dick Pierce   
   >>  wrote:   
   >>   
   >>   
   >>>Since energy is power integrated over an interval of time,   
   >>>we have all the information we need. The power is whatever   
   >>>the scaled sample value is. The interval is 1 sample period.   
   >>>Thus the energy is knowable.   
   >>   
   >>   
   >> The sample period is the interval between samples, not the duration   
   >> over which a sample is integrated. As far as I know, all ADCs sample   
   >> an instant as the edge goes low.   
   >   
   >No, for simple implementation reasons, the aperture,   
   >while small, is not zero. It is much smaller than   
   >the sample interval, but the fact that is is non-zero   
   >leads to a seldom-quoted A/D spec called "aperture   
   >error". But, as I mention elswhere, sampling theorom   
   >suggests that the difference between an aperture of 0   
   >and an aperture approaching a sample width is   
   >irrelevant to the resulting data.   
   >   
   This is all true, I accept that you have trumped my nit-pick with an   
   even smaller nit-pick (and so ad infinitum)   
      
   >> Energy at an instant is always zero,   
   >   
   >Mr. Einstein muight disagree, given that mass   
   >can exist during that same instant.   
   >   
   Things approaching zero gave Mr Einstein considerable trouble. He   
   wasn't at all happy about quantum mechanics.   
      
   >> whereas power at an instant is whatever it is.   
   >   
   >But, as you will probably agree, there are no "instants"   
   >in any practical system we can build.   
      
   No, no instants - but we do go an awful lot smaller than the sampling   
   interval.   
      
   d   
      
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