In 1951, the late professor Katsumi Imahori has designed a new speech frequency analyzer and named "Phonoscope. " Successive improvements have been made on this instrument with the aim of applying it to the speech correction method for the deaf children, and the investigation on representation of speech sounds for the normal and deaf people has been carried on with this "Phonoscope. " Phonoscope is a kind of direct speech translator, making spoken speech sounds visible by means of position and trace of light-spot on the phosphorescent screen of a cathode ray oscilloscope. The horizontal axis on the screen corresponds to the zero crossing (positive-going) frequency of the partial speech sound passed through a low pass filter with the cut-off frequency of 800 c. p. s. , while the vertical axis corresponds to the zero crossing (positive-going) frequency of the partial speech sound passed through a high pass filter with the same cut-off frequency as the above. The results of the vowel representation by Phonoscope are as follows: (1) The difference of the vowel distribution between adults (20-30 in age) and children (11-13 inage) was partly seen, and the authors were able to set the characteristic region of each vowel on the screen. (2) For the deaf children, the trend was shown that the light-spots representing vowels spoken by the deaf children were located outside the characteristic region for the vowel of normal people, on account of the lack of clearness in their pronunciation. And this trend was shown more strongly with increasing loss of hearing. This result agrees with that of our preliminary test on their aural articulation. (3) So it may be hoped that the Phonoscope will be usable as a means for speech correction in the deaf children.
The design of the Tuning Bar "Onpen" loaded with additional masses is explained in this paper. The design charts for the lowering of resonant frequency and transferring of nodal points by addition of concentrated masses are also presented here. This tuning bar which vibrates transversally to its long axis, is used as a standard of low audio frequency and its stability is proved very good. Three types of the tuning bar are investigated and they are; (a) Center Additional Mass Type, (b) Both End Additional Mass Type and (c) Center-Both End Additional Mass Type. By adding concentrated mass in any point of the tuning bar, the nodal points at resonance are transfered to any position from the nodal points in the non-loaded case, but in the case (c) if Center Mass/End Mass=3. 29, the nodal points of the 1st mode are identical to those of the bar with no-load.
Experiments on the internal heating effect of ultrasonic waves in high polymers were performed, giving the following main results. (1) For the case of radiation of the ultrasonic waves into the polyvinylchloride plates, the temperature rise by the absorption of ultrasonic waves are in a comparatively good agreement with the calculation; the value in the depth of 3 mm attaining to 70-80 ℃, even when a small portable ultrasonic apparatus of frequency 960 kc and intensity of 2 watt/cm^2 is used. (2) When the ultrasonic waves are radiated into two high polymer plates glued together by a proper adhesive, it is possible to make the temperature rise in the rear plate rather higher than in the front plate, provided the former has a very high absorption coefficient for ultrasonic waves. Similarly the high polymer plates can be efficiently heated even through thick metal plates, owing to the negligible absorption in metals and the selective ultrasonic absorption in high polymer. (3) The time required for adhesion (by Araldite 121) of two high polymer plates is extremely shortened by ultrasonic irradiation, because of the promotion of the polymerization of adhesive by the internal temperature rise. These experiments suggest that it is worth while to investigate the ultrasonic waves from the viewpoint of internal heating, even though these may be many limitations and difficulties in adaptability, as compared with the widely used radio-heating apparatus.
The effects of the shape and volume of the reverberation chamber on the measured absorption coefficient are discussed here. Reverberation chambers used for this research were two chambers in our institute, which were constructed in the same manner except for the shape and the volume. Same test specimens and measuring apparatus were used in this research, making it possible to investigate purely the effect of the shape and volume of the chamber. At first, the absorption coefficient of test specimen was measured in chamber No. 1 (volume 513 m^3, non-parallel walls). In this case, it was independent to the position of microphone and test specimen, as reported earlier. On the other hand, in the case of chamber No. 2 (6 m×4 m×5 m, rectangular parallelopiped), it was shown that the absorption coefficient was affected appreciably by these measuring conditions, especially for large absorption. Thus, in some cases, the absorption coefficients measured in both chambers differ from each other. Only under the specially selected measuring conditions, the absorption coefficient coincides fairly well, in general, the coefficient by chamber No. 2 is smaller than that of chamber No. 1. By considering the behavior of sound waves in both chambers, it is concluded that the shape of the reverberation chamber plays an important role for the uniform distribution of sound energy. As to the absorption coefficient defined by Sabine's formula, is should be the coefficient which is unaffected by the position of microphone and test specimen. When such a phenomenon as shown in chamber No. 2 occurs in the reverberation chamber, it is necessary to be careful of the measuring conditions; or else it would lead to erroneous results if the mean value of absorption coefficient is simply taken on several microphone position.