著者

二階堂 誠也

出版者

公益社団法人 計測自動制御学会

雑誌

計測と制御 (ISSN:04534662)

巻号頁・発行日

vol.19, no.3, pp.325-332, 1980-03-10 (Released:2009-11-26)

参考文献数

19

著者

難波 精一郎 桑野 園子 二階堂 誠也

出版者

一般社団法人 日本音響学会

雑誌

日本音響学会誌 (ISSN:03694232)

巻号頁・発行日

vol.38, no.4, pp.199-210, 1982

被引用文献数

3

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The effects of noise, distortion and band limitation on the tone quality of broadcasting sounds are investigated using the method of continuous judgment by category. The advantages of this method are that the long-term program can be used as stimulus as it is, and that subjects listen to the program without paying attention to any specific deteriorative conditions. Popular songs with conversation between an announcer and singers broadcasted by NHK FM are used as source program. The duration is about 23 minutes. Four kind of noise, three kinds of distortion and three kinds of band limitation are added on the program. Twenty subjects judge the instantaneous tone quality using eight categories. The effects of the deteriorative conditions are compared with one another in the same context. As a results, it is found that this method is appropriate to evaluate the tone quality of broadcasting sounds in a natural listening attitude. And it is confirmed by the experiment using this method that noise has the greatest effect on the tone quality, and that distortion also plays an important role in the estimation of the tone quality when either noise or band limitation is not added.

著者

二階堂 誠也

出版者

一般社団法人日本音響学会

雑誌

日本音響学会誌 (ISSN:03694232)

巻号頁・発行日

vol.28, no.9, pp.485-495, 1972-09-01

被引用文献数

20

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The conventional measuring method of nonlinear distortion using one or two tones of a fixed level does not always provide an objective value of distortion which agrees with the subjective sound quality of speech or music signal passing through the apparatus or the system to be measured. To find a better agreement, the distortion produced in the actual performance of the system should be obtained, and the distortion components appearing in various frequency bands should be extracted separately. A measuring method that meets these requirements is proposed in this paper. Fig. 1 shows the principle. As a test signal, a wide-band signal whose spectrum is similar to that of speech or music is used. The test signal is applied to the system to be measured after removing the narrow band components with band-elimination filter. Distortion components that appear in the eliminated band are extracted with an appropriate band-pass filter having the same frequency as that of the band-elimination filter. In this way the distortion component appearing in a specified frequency band is extracted, and the whole spectrum of distortion is also obtained by using pairs of filters of various central frequencies. Perceptibility of nonlinear distortion for three kinds of typical program sound was obtained as a function of frequency of distortion components using a distortion circuit having an input-output characteristics as shown in Fig. 6. The results are shown in Fig. 11, from which it is clearly seen that the distortion appearing in the high frequency band is much noticeable. Results of this measurement and a few additional experiments were discussed from the viewpoint of masking, and it was shown that the perceptibility of distortion components in a specified frequency band is mainly determined by the signal level in the same and the neibouring frequency bands, and that the just perceptible level of distortion is almost constant when the level is given relative to the signal level of the same frequency band as far as a fixed program signal is concerned.