Online ISSN : 2432-2040
Print ISSN : 0369-4232
29 巻, 8 号

• 三井田 惇郎
原稿種別: 本文
1973 年 29 巻 8 号 p. 445-450
発行日: 1973/08/01
公開日: 2017/06/02
ジャーナル フリー
It is important in the acoustical engineering to calculate the amplitude of reflected wave from a target. The calculation method has been developed by J. Saneyoshi, who defined the "sound reflectivity of the target" and derived analytically the approximate formulas of the reflectivity. The reflectivity expresses the ratio of the sound pressure of the reflected wave from the target at the position of the sound source to that of the reflected wave at the same position when the target is replaced by an ideally reflecting infinite normal plane. This formula for a circular plate is given by Eq. (10), which is fairly simple and practical. But as shown in Figs. 7 and 8, the discrepancy increases between the results of its numerical calculations and the actual behavior of the reflected wave when the value of the abscissa R/√λX is increased greatly or the distance between the transducers and a target becomes small in comparison with the size of a target. In this paper, the accurate solution for the reflectivity of the rigid targets of simple shape, such as circular plate and square plate, were derived which is applicable to the above case. As shown in Fig. 1, the velocity of the air particles on the target which is located at a distance r from the sound source is given by Eq. (2); φ_i is the velocity potential of the incident wave and k is the wave length constant. The reflected wave can be considered to be equal to the radiated wave from the target which is vibrating at the velocity of -V_N without incident wave. So, the absolute value of the reflectivity is given by Eqs. (12) and (13). Assuming that the shape of the target is circular, the equations are simplified in the form of Eq. (14). This equation becomes Saneyoshi's relation when √X/λ is increased up to infinity. The numerieal result of these equations are shown in Figs. 2 and 3. Some experiments were executed so as to verify the validity of above theories. These were performed in the air at the frequency of 39. 90 kHz. Fig. 4 shows the arrangement of the apparatus in the experiments. Two piezoelectric transducers were put on the axis of the circular plates were made of hard plastics. The pulse width of the sound wave from the transmitter was 1. 38 ms. The amplitude of the reflected pulse was measured on the screen of the C. R. O. . Figs. 5 and 6 show examples of the results of these experiments. Figs. 7, 8 and 9 show experimental and precise theoretical values of R/√λX divided by the approximate values obtained from Saneyoshi's equation when the reflectivity is minimum. The results of the experiments were in qualitatively reasonable agreement with the numerical results of this precise method.
• 本岡 誠一, 奥島 基良
原稿種別: 本文
1973 年 29 巻 8 号 p. 451-457
発行日: 1973/08/01
公開日: 2017/06/02
ジャーナル フリー
• 伊藤 勝彦, 森 栄司
原稿種別: 本文
1973 年 29 巻 8 号 p. 458-464
発行日: 1973/08/01
公開日: 2017/06/02
ジャーナル フリー
The resonator with directional converter was analyzed already. However, the converter is usually used as an element in a system of a vibrational transformation rather than a separate devics ; so that, it will be very convenient for understand a vibrational system as a whole, if the converter can be represented by an electrical equivalent circuit. From this point of view, the authors tried to analyze a L-L-type converter by its electrical equivalent circuit. The converter was divided in two principal parts, each part of four bars and one connecting part. Each part of bars was expressed by a four-terminal network of a distributed constant circuit and a connecting part was expressed by a four-terminal network of a concentrated or lumped constant circuit. Then the converter was indicated by four terminal network (see Fig. 2〜5), as vibrational modes of the converter in resonances were symmetric with respect to two axes. Thus, the frequency equation (35) and the equation (37) of the vibrational velocity ratio at each free end of the converter were derived. From this study, it was found, by referring to the other report, that these two equations were applicable to the converter with the connecting part which is small enough as compared with a wavelength of two axial directions, and were able to describe well its vibrational characteristics also.
• 戸塚 良則, 安広 輝夫
原稿種別: 本文
1973 年 29 巻 8 号 p. 465-472
発行日: 1973/08/01
公開日: 2017/06/02
ジャーナル フリー
This paper describes a new method of feature extraction from speech spectra based on multi-category linear discriminant function. Five Japanese vowels pronounced by 24 male speakers and 26 female speakers were analyzed by a filter bank (Fig. 1). Then four components were extracted from the output of the filter bank by this method and a vowel feature space was constructed by these four components (Fig. 3). 96% of these vowels were identified correctly using only two of the four components and 98. 6% using all the four components. It was shown that this method gives a better result than principal-component analysis under the same condition (Figs. 4 and 5). The coefficients calculated from the sample vowels were also applicable to new sample vowels (Figs. 6 and 7). Furthermore, the first and the second components were found to be highly correlated with the first and the second formant frequencies, respectively (Figs. 8~11). The trajectories of combined vowels /ie/, /ia/, /io/ and /iu/ in the first and the second component plane were similar to their trajectories in the F_1 - F_2 diagram (Fig. 12). From these experimental results, this method is expected to be useful for real time feature extraction from speech signals.
• 野村 浩康, 馬場 恒孝, 黒木 明徳, 宮原 豊
原稿種別: 本文
1973 年 29 巻 8 号 p. 473-477
発行日: 1973/08/01
公開日: 2017/06/02
ジャーナル フリー
The ultrasonic velocities of the mixtures of benzyl alcohol and methanol, ethanol, n-propanol and n-butanol were measured with a high pressure type ultrasonic interferometer at a frequency 4 MHz. The measuring pressure was up to 300 atm and the measuring temperature was 30℃. The ultrasonic velocities of these alcohol mixtures increased with the increase of pressure parabolically and decreased with the temperature rise linearly. As an illustrating example of experimental results, the pressure and temperature dependence of the ultrasonic velocities in these mixtures were shown in Fig. 1 and 2 for the mixtures of benzyl alcohol and n-propanol. From these results, the non-linearity parameter, B/A, were determined. These values were summerized in table 5-8. As is seen in these tables, the non-linearity parameters were almost constant in spite of the fact that the pressure coefficients of ultrasonic velocities varied lineary with the mole fraction in each of the alcohol mixtures.
• 白砂 昭一, 川上 福司
原稿種別: 本文
1973 年 29 巻 8 号 p. 478-483
発行日: 1973/08/01
公開日: 2017/06/02
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• 五十嵐 寿一
原稿種別: 本文
1973 年 29 巻 8 号 p. 484-
発行日: 1973/08/01
公開日: 2017/06/02
ジャーナル フリー
• 厨川 守
原稿種別: 本文
1973 年 29 巻 8 号 p. 485-489
発行日: 1973/08/01
公開日: 2017/06/02
ジャーナル フリー
• 中村 昭
原稿種別: 本文
1973 年 29 巻 8 号 p. 490-
発行日: 1973/08/01
公開日: 2017/06/02
ジャーナル フリー
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