If we would like to discuss in technical terms , all that is fully subjective has to be considered out .
Questions and answers ( theory of linear systems ) : 1) If we put a single or multiple monochromatic signal in a system with flat response , linear amplitude response and flat group delay , will the signal be distorted ? NO 2) If we put a single monochromatic signal in a system with flat response , NON linear amplitude response and flat group delay , will the signal be distorted ? YES 3) If we put a multiple monochromatic signal in a system with flat response , NON linear amplitude response and flat group delay , will the signal be distorted ? YES 4) If we put a single monochromatic signal in a system with flat response , linear amplitude response and NOT flat group delay , will the signal be distorted ? NO 5) If we put a multiple monochromatic signal in a system with flat response , linear amplitude response and NOT flat group delay , will the signal be distorted ? YES .NEW SIGNALS (DISTORTION )WILL BE CREATED FROM THE GROUP DELAY BEING NOT FLAT ,LIKE WHEN THERE IS ONLY NON LINEAR AMPLITUDE RESPONSE . 6) Does the human being perceive audio distortion ? YES 7) Is the annoying effect of a perceived distortion proportional to the distortion ? YES 8) Are the human being able to discriminate between the same distortion coming from the effect of non linearity or from the group delay being not flat . NO . THE INSTRUMENTS ARE NOT ABLE TOO TO DO THIS WHILE ONLY MEASURING THE TOTAL EFFECT . 9)Does this mean that the effect of both non linearity and not flat group delay is the creation of new signals that was not present in the original composite signal ? YES 10) Can we put a large number of persons in a controlled environment and perform audio tests to correlate the values of the parameters of amplitude distortion or group delay with a quality grade scale ? YES , THIS NORMALLY DONE FROM SEVERAL STUDIES GROUPS OR TECHNICAL BODIES ( ETSI , ITU , FCC , AES EBU , MPEG ETC. ) . 11) What are the typical recommendations of the limit of the technical parameters that has to be reached for professional equipements ? IF POSSIBLE THE DEGRADATION HAS TO BE AN ORDER OF MAGNITUDE LESS OF WHAT IS PERCEIVED IN THE SUBJECTIVE TESTS . It is late and I could have made errors , but I hope that the overall sense could be clear . 73-Claudio I1RFQ
