音質の総合評価

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A model of the process of evaluating reproduced sound quality was examined experimentally. As shown in Fig. 1, it was assumed that there was such relationship between the preference scale of sound quality R and multidimensional sensory scale D_i(i=1, 2. . . , n), as R=w_iD_i, where w_i=W(L, S, A), L: listener groups classfied in terms of the similarity of preference, S: musical signals classfied by their effect on w_i, A: age(time) and D_i=φ_i(t_j, s_i), t_j: a physical parameter of a transmission system, s_i: components of S, contributing to D_i. To examine this model, three experiments were made. The first and the second experiments were made to examine a linear equation relating to above-mentioned R and D_i. Stimulus conditions are shown in Table 1, and the block diagram of experimental circuits is shown in Fig. 2. Two of classic music(A: synphony, B: string quartet) were used as the source S, and presented to ten listeners under the above stimulus conditions. By means of the method of paired comparisons, the preference scale R and two sensory scales D_1(sensation of noises, mainly related to nonlinear distortion) and D_3(sensation ob treble, mainly related to low-pass filtering frequency) were obtained. From three scales the least square solutions of w_1 and w_3 were calculated. These values are shown in Fig. 3 and 4. Finally, from the scale values of D_1 and D_3 and estimated weights w_1 and w_3, estimated value R^^~ of preference scale was calculated. As shown in Figs. 3 and 4, the coincidence of observed value R and estimated value R^^~ was fairly good. This seems to prove the adequacy of the model. Fig. 5 shows the coincidence of R and R^^~ with four dimenstional sensory scales (D_1-D_4) taken into account. This third experiment was made to examine the stability of w_i. If w_i is only affected by L, S and A, and not by t_j, and once w_i for definite L and S is obtained, as far as L and L and S are fixed, R^^~ for various t_j will be able to be estimated from the curves of φ_i. These estimated values of R^^~ should coincide with observed R for such t_j. Fig. 6 shows the curves, in which w_i was calculated, and Fig. 7 shows tho estimated scale values of D^^~_<2i> for the second set of t_j, which is different from that used in determing w_i (the first set of t_j). From such predetermined w_i and estimated D^^~_<2i>, estimated value R^^~_2 of preference scale was calculated. As shown in Fig. 8, estimated value R^^~_2 and obserbed value R_2 for the second set of t_j coincided with each other very well again. If this model is proved to be adequate, and when a listener group and a source classification are given, it will became possible to design a transmission system, the sound quality of which is liked best by the listener group.
社団法人日本音響学会の論文
1966-11-30

音質の総合評価

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