日本音響学会誌
Online ISSN : 2432-2040
Print ISSN : 0369-4232
9 巻 , 2 号
選択された号の論文の8件中1~8を表示しています
  • 日本音響学会音響標準委員会
    原稿種別: 本文
    1953 年 9 巻 2 号 p. 69-71
    発行日: 1953/06/30
    公開日: 2017/06/02
    ジャーナル フリー
  • 日本音響学会音響標準委員会
    原稿種別: 本文
    1953 年 9 巻 2 号 p. 72-82
    発行日: 1953/06/30
    公開日: 2017/06/02
    ジャーナル フリー
  • 能本 乙彦, 池田 拓郎
    原稿種別: 本文
    1953 年 9 巻 2 号 p. 83-129
    発行日: 1953/06/30
    公開日: 2017/06/02
    ジャーナル フリー
  • 大野 壽彦, 河合 平司
    原稿種別: 本文
    1953 年 9 巻 2 号 p. 130-132
    発行日: 1953/06/30
    公開日: 2017/06/02
    ジャーナル フリー
    When the external auditory cannal is closed with an ear-plug, the absolute threshold values of bone-conduction hearing become smaller when frequency is lower than about 2000 cps and these threshold shifts have two peaks at about 150 and 800 cps, the values of these peaks seem to change with the age of the objects. The threshold shifts of a man, 21 years old , are about 30 db at 100 cps, 40 db at 150 cps, 25 db at 300 cps, 22 db at 500 cps, 20 db at 800 cps, 15 db at 1000 cps and 7 db at 1500 cps, and these values of an older person are smaller only at lower frequencies. The threshold values do not very by closing the external auditory cannal with an ear-plug in the person who has the perforated ear-drum and the karies of the malleus. The one peak at 150 cps can be explained by assuming the eardrum to be a system of mass and resistance which resonates with the cavity of the auditory cannal. The other peak at 800 cps is due to the resonance in the middle-ear mechanisms.
  • 実吉 純一
    原稿種別: 本文
    1953 年 9 巻 2 号 p. 133-139
    発行日: 1953/06/30
    公開日: 2017/06/02
    ジャーナル フリー
    The speed characteristics of the propeller noise of ship are measured in an experimental water tank. Instead of a model propeller, a rectangular iron bar is rotated by a 3kWD. C. motor. Ultrasonic noise is received with a 17. 5kc magnetostriction transducer, and audio ferquency noise with a moving coil type hydrophone with a thick rubber diaphragm. No noise except that due to mechanical vibration is detected at the speed under a critical speed of about 8m/s at the end of the bar, and a violent noise is generated when the speed is raised beyond the critical speed. The amount of bubbles produced by cavitation is measured at each speed, and its variation with the speed is similar to the noise voltage. If the depth of the rotationg bar is shallow that air is sucked into the water, some noise is detected even under the critical speed. For the investigation of the cavitation noise due to the roughness of outside surface of a ship at high speed, a wooden drum is replaced for the rotating bar, and several models of shellfish or head of rivet are attached on the cylindrical surface of the drum. The critical speed for these cases is 9-10m/s(17. 5-19. 4 knots). The author suggests, in conclusion, that a propeller and water can generate no noise without the presence of cavitation or bubbles.
  • 粟谷 丈夫
    原稿種別: 本文
    1953 年 9 巻 2 号 p. 140-146
    発行日: 1953/06/30
    公開日: 2017/06/02
    ジャーナル フリー
    Theoretical calculations were performed on the acoustic radiation pressure exerting on a cylinder, taking the effects of diffraction and inertia into account. The numerical calculations were carried out as for as the ratio of the circumference of the cylinder and the weve length is increased to 5. 0 for cylinders various materials in plane progressive and standing wave field in water.
  • 鳥飼 安生
    原稿種別: 本文
    1953 年 9 巻 2 号 p. 147-153
    発行日: 1953/06/30
    公開日: 2017/06/02
    ジャーナル フリー
    The Fresnel diffraction patterns by the ultrasonic field are theoretically investigated. They are produced by the so-called secondary interference method developed by Hiedemann and others for visualizing ultrasonic waves. The diffraction images appearing behind the phase grating, the progressive ultrasonic waves, the standing waves and the superposed waves are theoretically calculated and the results agree well with the experiments(cf. , the next paper). The present theory is the generalization of Nomoto's theoretical research on the same problem.
  • 蒲生 秀也
    原稿種別: 本文
    1953 年 9 巻 2 号 p. 154-164
    発行日: 1953/06/30
    公開日: 2017/06/02
    ジャーナル フリー
    The sampling theorem for bandpass filters is devoloped. We assign frequency bands 0-W, W-2W, . . . , (N-1)W-NW to bandpass filters, in order to discuss the signal analysis in the frequency-time domain. The elementary signals, of which examples are illustrated by Fig, 1 and 2, are u^k_n={sinkπ(2Wt-n)-sink-1π(2Wt-n)}/π(2Wt-n), k=1, 2, . . . , N, n=-∞, . . . , 0, 1, . . . , +∞ and make a complete system of orthogonal functions. Then the signal function can be expressed as f(x)=Σ^^N__&ltk=1&gtΣ^^&lt+∞&gt__&ltn=-∞&gta^k_nu^k_n, where a^k_n=f^k(n/2W):the coefficient is the amplitude sampled at every 1/2W sec of the signal f^k(t)separated by the k^&ltth&gtfilter. The sequence of sampled amplitudes is the amplitude modulation of pulse train having the repition frequency 1/T_s or 2W and these pulse trains have both side bands about each harmonic of the repitition frequency. When it is required to remake the continuous signal from the sequence of sampled amplitudes, we can realize the signal with any one of limited spectrums stated above by making pulses pass through the corresponding bandpass filter. The physical meaning of the "analytical signal" introduced by D. Gabor is discussed by showing the method which may realize the quadrature component of the analytical signal and by clarifying the independent variables of the analytical signal with limited spectrum. The analytical signals of the elementary signals stated above are obtained, and are expressed as Ψ^k_n(t)=exp{i2k-n)}sinπ(Wt-n)/π(Wt-n), k=1, 2, . . . , N, whose examples are illustrated in Fig. 5 and 7. From the complete orthogonality of the analytical signals mentioned above, a sampling theorem is derived and is expressed as Ψ(t)=Σ^^N__&ltk-1&gtΣ^^&lt+∞&gt__&ltn=-∞&gtC^k_nΨ^k_n(t), where C^k_n=∫^∞_-∞ψ(t)Ψ^k_n(t)dt=ψ^k(n/W), and bar means to take complex conjugate and ψ^k(n/2W)is the n^&ltth&gt sampled amplitude of the analytical signal separated by the filter. (It corresponds to the result obtained independently by J. Oswald. )The signal analysis in the frequency-time domain is discussed by using the results described above. We may consider that the sampling theorems stated above contain the so-called uncertainty relation in the spectral analysis, and these theorems may be more convenient to estimate the amount of information of the signal than Gabor's treatment, because our sampling coefficients are independent of each other.
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