Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site unc.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxj!houxm!vax135!cornell!uw-beaver!tektronix!decvax!mcnc!unc!rentsch From: rentsch@unc.UUCP (Tim Rentsch) Newsgroups: net.audio Subject: Re: CD reflections Message-ID: <92@unc.UUCP> Date: Tue, 22-Jan-85 23:37:56 EST Article-I.D.: unc.92 Posted: Tue Jan 22 23:37:56 1985 Date-Received: Fri, 25-Jan-85 21:09:56 EST References: <81@unc.UUCP> Reply-To: rentsch@unc.UUCP (Tim Rentsch) Organization: CS Dept., U. of N. Carolina at Chapel Hill Lines: 32 Summary: In article newton2@ucbtopaz.CC.Berkeley.ARPA writes: > > is that information gets fuzzier (and so reconstruction gets > worse) as the frequency gets closer to the nyquist limit." > > Like so much opinion presented as "the actual fact" on net.audio, >this is just hogwash. "Fuzziness" is independant of frequency, up to or >even above the Nyquist limit, unless you consider fully precise aliased >components (resulting from sampling too seldom) to be fuzziness. Noise >and distortion are functions of the number of bits per sample and linearity. > Sorry for the misunderstanding. "Fuzziness" is, I admit, an imprecise term. I chose it for its intuitive appeal. The idea is that uncertainty in the sample can result in error in the reproduced sine wave, and that this error increases as the frequency gets closer to the nyquist limit. Think of this as another manesfestation of aperture uncertainty -- in the same way that jitter in *when* the signal is sampled can result in error in the amplitude of the sampled value, so uncertainty in the amplitude of the sampled value can be interpreted as error in the time when the signal is sampled. For a given delta t of uncertainty in sample time, this uncertainty affects high frequency signals more than it does low frequency signals, since perurbing a sine wave by 1% (say) of its period will have more effect than perturbing a sine wave by 0.1% of its period. To set the record straight: the explanation of fuzziness is my own. The existance of aperture uncertainty is sampling-theory-accepted fact. (Hope you're not still feeling grumpy), Tim