Flexurally vibrating bars used for mechanical filter are generally supported at their nodal points with slender steel wires. These wires are in many cases straight, but sometimes curved wires are used (Fig. 1). Their characteristics in vibration have not yet made clear. For the support wire of a mechanical filter, the consideration of the static stiffness of the wires and the frequency range to be practically utilized determines whether or not the curved wires are better than straight ones. On the otherhand, the curved wire is also used in practice as a bridging coupler over the adjoining resonators for the mechanical filter with attenuation-poles characteristic (Fig. 2). As the coupler of a narrow-band mechanical filter, a ∩︀-shaped coupler is suitable for practical use because the stresses are less concentrated at its curved portion than a ⊓︀-shaped coupler. This paper deals with the analysis of these curved wires and attempts to make their vibration characteristics clear. For the matrix analysis applied effectively in this paper, the straight portions of the wire are considered as a single section whereas the curved portions are divided into several elements approximated by a series of straight sections (Fig. 3 to 5). In the first part of this paper, the models of the curved wires and the matrices for the straight section are presented. Two different matrix equations are presented. Two different matrix equations are separately utilized for the segment. That is, one is Equation (1), which is used for the calculation of the dynamic characteristics and the other is Equation (5), for the calculation of static characteristics. In the second part of the paper, methods of calculating the input impedances, the resonant and the antiresonant frequencies are described (Figs. 6 and 7). Finally, the numerical results are demonstrated (Tables 1 and 3, Figs. 8 to 13). From these results, the following conclusions are drawn. (1) In the application to the support wire, the stiffness of the curved wire is less than that of the straight wire, so that curved support wire less affects the resonant mode of the vibration, but its frequency range is narrower than that of the straight support. In addition, the curved support wire may not always be superior from the point of the resilience against the rigid body vibration due to external shock. (2) Concerning the application to the bridging coupler, the coupling stiffness is greatly affected by very small change of the curvature. The resonances and anti-resonances appear repeatedly at narrow internals in the frequency characteristics (Figs. 11 and 12). (3) A coupler of the ∩︀-shape is superior to that of the ⊓︀-shape for the narrow-band filter applications, because it can provide small coupling stiffness (Table 3). (4) The equivalent circuit and element values of tee type are based on the numerical results.
A spoken-word recognition system composed of the following three steps has been in this research. That is, the first step is the extraction of the acoustic parameters, the second is the transformation of the acoustic parameters into a string of features, and the third is the transformation of the string of the features into a string of characters or some symbols which represents a word or short sentence. The use of the linguistic information is considered to be effective on the third step. On the first two steps, the local peaks in the short time spectra analyzed by a filter bank composed of 29 single peak filters of low selectivity are treated as the acoustic parameters. And some experiments on vowel samples uttered in isolation and in continuation by 31 male adults were carried out to investigate the effectiveness of the use of the local peaks. The usefulness of the local peaks for the recognition was proved by experiments. And the discrimination experiments on vowels and consonants in Japanese 20 city names uttered by 5 male adults by use of the static properties of the spectral local peaks were carried out. The scores of the discrimination were more than 80% expect for voiced stops (47%) and for some phonemes described in this paper. For the semivowels, liquid, unvoiced fricative/h/, stop consonants and choked sound, the dynamic property has an important part for the transformation of the speech segments into the phonemic symbols. Then, the discrimination experiments on the phonemes by use of the changes in local peaks and the variation in the total power of speech segments with time have been carried out as described in this paper. The speech samples are frequency-analyzed by a filter bank composed of 29 single peak filters as Q≒6. The center frequencies of the filters are every 1/6 octave from 250 Hz to 6300 Hz. Three major spectral local peaks, P1, P2 and Pe3 are picked up in every 10 ms from the six largest local peaks of the frequency spectrum obtained by analysis with the filter bank by applying two-peak processing rules. The phonemes were discriminated use of the changes in these local peaks and the variation in the total power of speech segments with time. From the speech samples of 20 city names uttered by 5 male adults, the standard patterns for the discrimination of phonemes were made. The scores of the discriminations of phonemes in the speech samples were as follows; /w/:65%, /j/:80%, /r/:68%, /h/:60% (in the initial position of words) and 87% (in the other position of words), /p, t, k/:97% and /Q/:100%. By using the above-mentioned standard patterns, a discrimination experiment was carried out with other 146 city names and the following scores were obtained; /w/:42%, /j/:71%, /r/:74% and /h/:27% (in the initial position of words) and 88%(in the other position of words). These results give us the expectation for the effectiveness of this method of feature extraction and the transformation into the phonemic symbols in the speech recognition system. And some recognition experiments were carried out. The 20 city names from which the standard patterns were made were used for the first time, and 96% of 100 samples were correctly recognized. The 20 city names uttered by other 3 male adults were used for the second experiment, and 86% of 60 samples were correctly recognized. The recognition score is considered to be increased by the improvement in the linguistic processing in the recognition system.
The object of this experiment is to clarify the effect of rising speed of a sound on its annoyance. White noise was used as stimulus sounds whose rising speed ranged from 25 dB/s to 1000 dB/s. The idealized time pattern of signal employed in the judgment test is shown in Fig. 1, and some physical characteristics of the stimulus sounds are presented in Table 1. Ten male and ten female students with normal hearing acuity served as the subjects. They were given abundant practice before the actual experiment began. Subjects were instructed to judge the whole perceived magnitude of the sound, for example, annoyance, unpleasantness and so on. The sounds were arranged at random with respect to test variables and presented to the subjects through a headphone in the sound proof room. Annoyance of sounds thus presented are estimated by the subjects by the method of magnitude estimation. The number denoting annoyance of a sound, the level and rising speed of which were 80 dB and 1000 dB/s respectively, was arbitrarily equated to 1, and the other annoyance estimates for each subject were transformed with reference to this value. The results obtained as shown in Fig. 3 that the annoyance expressed as the logarithm of the ratio of annoyance increases linearly with the logarithm of the rising speed. The following equation was obtained by multiple regression analysis with two independent variables: logψ=0. 0278L+0. 0346R_s-2. 269, where ψ is the ratio of annoyance, L is the peak level (dB), and R_s is the rising speed (dB/s). From the equation, it can be seen that annoyance becomes twice when the level of sound increases by 10. 8 dB (Fig. 4). From this relation, ψ is expressed as the relative sound pressure level (RSPL), which is shown in the left ordinate of Fig. 3. To show the average annoyance increase with rising speed, the results shown in Fig. 3 are averaged and plotted in Fig. 5. However, since acoustic energy of stimulus decreased as the rising speed increases, the results are corrected so that the annoyance increase due to steepening of rising speed can be obtained for equal energy stimulus (Fig. 6). Difference of sound pressure level corresponding to the difference of annoyance between the sounds with rising speeds of 25 dB/s and 1000 dB/s was about 2. 6 dB.
In the preceding paper, the authors reported the results of surface heating and absorption heating of a small solid body irradiated with ultrasonic waves in a liquid medium. We continued this research further so as to elucidate some unclarified phenomena. This report consists of two parts; one is concerned with further experiments on surface heating itself and the other is concerned with heating in general including absorption heating of various metallic and plastic materials. 1. Surface Heating (1) We attempted to find the relation between the heating and the surface roughness of the specimen. The apparatus used is shown in Fig. 1. The specimens were disks of fused quartz with a diameter of 4 mm and a thickness of 2 mm. The roughness was made by ditching as shown in Fig. 2. The number, depth and width of the ditches were changed. The results are shown in Fig. 6. The temperature rise is almost linearly proportional to the actual area of the surface. (2) We investigated how the heating of the specimen varied with incident angle of waves. The specimen used was a fused quartz plate, with an area of 20×20 mm^2 and a thickness of 2 mm. Fig. 7 illustrates the arrangement of the experiment. The temperature rise was measured at the center of the front surface by means of a very tiny thermocouple and its plate was rotated around the vertical axis as shown in the figure. The temperature rise is the solid curve of Fig. 8. In the smaller angle region (up to about 10°), we could not get steady results because of the standing wave effect, but the temperature rise increased with increasing angles between about 15°and 80°. This phenomenon was assumed also to be due to surface heating, because the velocity component of the liquid particles parallel to the surface increased with the above angles. (3) We investigated the relation of the heating and the surface materials of the specimens. On the fused quartz plate mentioned above, several kinds of metal film were prepared by vacuum deposition and also a thin plastic film was painted. The method of measurement was the same as that of (2). The authors found that the rise in temperature were almost independent of the surface materials deposited or pained, and were about the same as the result in the case of bare fused quartz plate. We assumed that the reason for this phenomenon was that the wetting between these materials tested and oil should be almost of the same order. 2. Heating of various materials We tried to investigate the relation of surface heating and absorption heating of various materials with different ultrasonic absorptions. The shape of the specimen and apparatus of measurement were the same as 1. (1). The depth and width of ditches were 0. 5 mm and 0. 2 mm respectively. The solid curves of Fig. 12 show the relation between viscosity of liquid and the saturated temperature rise of the specimen. The temperature rises of each of the materials for viscosity are expressed by equation (7), where θ is the temperature rise, η the coefficient of viscosity and A, α constants. The first term corresponds to surface heating, the second to absorption heating and the third to the heating of the liquid itself. The result is shown in Fig. 13. From these graphs, we could obtain the approximate magnitude of surface heating and absorption heating of various materials. For materials with low absorptivity, such as fused quartz, the main heating was that of surface heating. For materials with absorptivity of middle grade, such as Sn or Pb, both surface heating and absorption heating appeared together. For materials with high absorptivity, such as plastics, the heating was absorption heating.