In the application of longitudinal vibration system is usually of one-dimensional construction from the driver to the portion utilizing vibration energy. However, the authors are sure it may be more convenient that ultrasonic energy can be transmitted from the driver to the other direction. From this point of view, the suthors have reported in this journal the resonator with basic directional converters of the following three types, (A) L-L type converter, (B) L-L-L type converter, and (C) R-L type converter. These converters can be used as any part or unit of the vibration system from the driver to the portions utilizing vibration energy, and constructed as a three dimensional vibration system. In this paper, we analyzed the radial vibration of a hollow cylinder with various sections in general and utilizing this result analyzed the R-L type converters with various sections as shown in Fig. 4, and formulated the equations necessary for the design of these converters as given in equations from (3-7) to (3-10) and from (4-3) to (4-6). Then the converters were designed and tricllymanufactured, and the vibration characteristics of the converters were measured. As the result, it was found that the values of measurement by experiment are in good agreement with those by calculation within about 10%. In actual use of these converters, we trially made another converter with large connecting part of this type as shown in Figs. 10-12. We obtained a result that the experimental values of measurement are in good agreement with those of calculation within about 20% as shown in Figs. 13-15.
The temporal process of frequency analysis in the ear has been investigated from some aspects, but further investigations are required because it involves complicated problems owing to the neural complexity. Actually the ear shows various response modes depending on the stimulus. In this paper, we describe the results of four experiments carried out using tone bursts of short duration, and frequency selectivity for short durations. The results obtained as follows:1) Experiment on simultaneous masking when the signal has the same duration as the masker. Fig. 1 shows a schematic diagram of the stimulus presentation. The masked thresholds obtained as functions of duration and signal frequency are shown in Figs. 2 and 4. In Fig. 2, the sharpness of the masking curve increases with the duration. The masking curve is much sharper for our experiments than the steady-state response curve of the basilar membrane calculated from the model of Flanagan even for a duration of 5 msec (Fig. 3). A comparison between Figs. 2 and 4 shows that the threshold shift at the center frequency for the narrow-band masking noise is smaller than that for broad-band noise when the duration of the stimuli are shorter. This result can be interpreted by assuming that the critical band in the ear is wider for short durations than normal durations. 2) Experiment on trill threshold. Two tones of different frequencies were alternated successively from several times to one hundred or more times per second (Fig. 5). When the difference in frequency was large, the alternation sounded like two unrelated, interrupted tones. The just noticeable frequency difference (ΔF) as so perceived was measured as functions of duration and interval (Figs. 6 and 7). ΔF increases with decreasing duration of the signal and the data are described reasonably well by a straight line with a slope of about-0. 5 on the logarithmic coordinates used here (Fig. 7). It is interesting that similar results were obtained by Liang and Chistovich (1961), Oetinger (1959), and Stevens (1952), namely, that the frequency difference limen is reduced in direct proportion to the square root of the increase in duration. 3) Experiment for comparison of loudness and pitch between sine and cosine pulses. Cosine phase sound is perceived as considerably louder and higher in pitch than sine phase sound for very short durations. The critical duration as so perceived was measured at signal frequencies of 250, 1000 and 4000 Hz (Figs. 8 to 10). The results shown in the figures can be explained assuming that there is a linear filter whose bandwidth is inversely proportional to the critical duration in the ear (Fig. 11). 4) Experiment on hearing threshold for complex sounds. The hearing threshold for multitone complex sounds composed of 1 to 24 sinusoidal tones evenly spaced 80 Hz apart were measured for signal durations of 5 msec and 200 msec (Fig. 12). Similar results are obtained for both durations (Fig. 13). These results can be interpreted if the critical band assumed to be independent of the duration. Thus, in experiment on the signal detection of noise (simultaneous masking) and the experiment on frequency discrimination (trill threshold), the critical band appears to widen with decreasing duration. However, in the experiment on the energy summation along the frequency axis (hearing threshold and loudness), the critical band appears to remain constant.
In the theoretical analysis of phonograph pickup, there are some researches based on the conception of one degree of freedom system, but it seems that any studies, in which the oscillating system is considered as of infinite degree of freedom have not yet been performed. In this paper the osciiating system of pickup is regarded as a simplified system shown in Fig. 1, and a theoretical analysis of an actual pickup (moving magnet type) as shown in Fig. 2, is carried out using eq. (1), thst is, the equation of motion in a bar with infinite degree of freedom. Under boundary conditions given by eq. (2) and eq (3), eq(5) is a solution of displacement for the pickup cantilever, which is needed to obtain some results, about frequency responses for example. The frequency response and the mechanical impedance characteristic are respectively calculated from eq. (8) and eq. (11), and several constants needed in the calculation are determined as shown in Table 1. Fig. 4 shows calculated freqency responses of an actual pickup, and the dotted line in the figure represents a response in case of very amall viscous damping. Fig. 5 and Fig. 6 show respectively phase angles and mechanical impedance characteristics. From these calculated results it is known that a pickup has generally three resonant points in the normal frequency range. Fig. 7 shows a measured frequency response of the actual pickup, and a true response of the vibrating system which is compensated by an electromagnetic frequency response of the pick up body (Fig. 10) is compared with the response previously calculated shown in Fig. 11. Fig. 8 shows a comparison between measured and calculated mechanical impedance characteristics. From these investigations it is made clear that the theoretical results approximately coincide with the experimental results, but it is known that this analysis does not always give satisfactory results in spite of considering the system as of infinite degree of freedom. Finaly a few shapes of vibration of the pickup cantilever are calculated, and some aspects of the bending cantilever are manifested to a certain extent. In future a study on the difference between theory and experiment will have to be accomplished.
As shown in Fig. 1, an optical heterodyne technique can be successfully applied for in-plane vibration measurement. The purpose of this paper is to make clear the design method and technical details to construct a measuring instrument based on this technique. For the purpose, a prototype apparatus is constructed and its performance is studied experimentally. It is ascertained that an in-plane vibration with an amplitude of 10Å at 20 kHz can be measured together with the velocity vector distribution. Figs. 2 and 3 show schematic diagrams of the optical system and an experimental setup respectively. Figs. 4 through 8 are photographs and schematic diagrams of main components. In order to determine the optimum conditions of the optical imaging system shown in Fig. 2, studies on mutual relations among beat signal amplitude, diameter of pinhole, and mean diameter of speckle are made. Fig. 10 shows the results of these studies and it is concluded that the diameter of pinhole should be a few times as large as that of speckle to obtain adequate beat signals. Figs. 13 and 15 are the results of performance test.