Reply To: Muzika-įrašas-atkūrimas

Audiofilas Forums Akustikos inžinerija Muzika ir atkūrimas Muzika-įrašas-atkūrimas Reply To: Muzika-įrašas-atkūrimas


    80-aisiais metais tarp objektyvistų ir subjektyvistų buvo kilęs disputas dėl garso technikos objektyvaus vertinimo. Objektyvistų pusei atstovavo žymūs garso mokslo atstovai (prof. Stanley Lipshitz, prof. John Vanderkooy, Thomas. A Nousaine,  David Clark ir kiti), išpublikavę gausybę mokslinių straipsnių garso inžinierių  asociacijos (AES) žurnale.  Straipsnių serijoje “The Great debate” garso mokslo atstovai aiškiai deklaravo, kad įrenginių/sistemos objektyvių techninių parametrų rinkinys pilnai leidžia nusakyti garso kokybę. Rekomenduočiau pavartyti šiuos straipsnius tiek objektyvistams, bet ypač subjektyvistams, nepripažįstantiems garso mokslo viršenybės.
    Straipsniais galėčiau pasidalinti asmeniniam skaitymui, su sąlyga, kad nebus platinami viešai.

    Stanley Lipshitz and John Vanderkooy, The Great Debate: Subjective Evaluation
    John Vanderkooy, The Great Debate- Some Reflections Ten Years Later
    Tom Nousaine, The Great Debate: Is Anyone Winning

    Trumpai anuos žymius debatus reziumuoja pirmojo straipsnio išvados.

    In summary, our position is that as yet we have not encountered audible phenomena for which we could not measure a possible cause. On the contrary, measurements easily show up differences where none are audible in careful listening tests. It may be difficult initially to associate a measurable effect with an audi*ble difference, but this should be done to advance the state of audio.Our findings are that level differences of 0.2 dB are audible if present over a fairly wide band, and we therefore suggest that A/В tests must have linear differences matched to 0.1 dB. This represents an amplitude difference of about 1% as the minimum amount detectable by the trained ear.

    Nonlinear distortions are also audible to the ear, and early work has long established that although a few tenths of 1% of low-order harmonic distortion may be audible on some sinusoidal signals, for music only about 1% distortion becomes audible. We have done tests with a circuit (Fig. 5) that produces controllable amounts of pure crossover distortion similar to that of a class В audio amplifier, and found that crossover distortion is not as audible as commonly supposed. On sine waves it is detected to levels of about 0.1% (on an average basis), because one can move the head into positions in the room where the fundamental is weak, but not the harmonics. On earphones the audibility is much poorer. On music signals the crossover distortion is about 1% before it becomes audible,3 and is most readily heard on solo piano music, where it appears surprisingly as a noise modulation.

    We emphasize that listening tests may produce sur*prises in the parameters that should be controlled. Our tests and those of SMWTMS indicate that a difference in absolute polarity of the audio signal is audible, al*though admittedly subtle. Particularly on percussive sig*nals there is a change in perceived depth, high-frequency detail, clarity and even level. Such words and others are commonly found in subjective reviews, and it is our belief that this may be due in part to the almost arbitrary signal polarity in much audio equipment. Thus relative polarity must be rigorously maintained in an A/В test.

    As a final exhortation, we urge the audio community to improve and continue well-controlled subjective tests. Not all hypotheses will be backed by rigorous tests, but some corroborating evidence ought to be given.

    • This reply was modified 4 weeks, 1 day ago by BelasBelas.