In this first report on nasals, we study the two kinds of nasals, namely; the critical | &a;| and the typical |&b;|. Both of these are obtained only when sounded through the nose, related thereby to the fine structure of timbre-patterns. We deal with these nasals for the purpose of clarifying the fundamental features of so-called nasality.
Here we observe and discuss the structural recurrency or periodicity which prevails over and regulates the fine detail of structure throughout the whole pattern of nasals and which comes in close contact with the peculiar characteristics of output level of nasals.
This paper intends to report on investigations made on effects of street noise upon the learning of pupils in school rooms. 4. 357 pupils among 6 primary, 3 junior and 2 senior schools in Osaka City were selected. The situations of these schools, in which the subjects were learning, were noisy. The following investigations were performed: (1) The psychic and somatic response of pupils on the noise caused by traffic, whistle etc. by means of questionnaire method. (2) Kraepelin's tests and syllable articulation tests in noisy and quiet school rooms. The following results were obtained: (1) The sound levels encountered in noisy school rooms (91 rooms) ranged 40-65 phons and in about one quarter of these rooms, the levels were 55 phons or higher while the sound levels in quiet school rooms (investigated as control) ranged 40-45 phons. (2) Among the replies by the subjects who studied in noisy school rooms with the sound level higher than 55 phons, more than 50 % filled out "Yes (measuring, difficulty)" regarding to the items concerned with emotion and perception of speech while same answer was given by 31 % of the subjects regarding to mental works and 24 % regarding to physical conditions. (3) The statistical study of Kraepelin's tests revealed that there were no significant differences in the work amount, the percentage of errors the percentage of rest efficiency between the tests in noisy and quiet school rooms. (4) In noisy school rooms, with noise level higher than 55 phons, articulation of syllable decreased especially at the rear seats. (5) The noise level in school rooms, which are exposed to street noise, seems necessary to be lower than 55 phons for satisfactory learning.
This paper deals with a qualitative consideration of experimental results of the evaporated thermo-couple used as an intensity detector in a sound field. This special thermo-couple is made of evaporating Bi and Sb or their alloys on the mica or collodium film in a vacuum. It has been found that the electro motive force generated in a sound field is a direct current E. M. F. proportional to the square of the sound pressure. From this fact, the possibility of using the special thermo-couple as a measuring instrument of sound intensity was established. The frequency range of the thermo-couple in this experiment is from 200 to 5000 c/s. This instrument does not indicate the alternating electro motive force induced by the sound wave, so the time constant of the thermo-couple is not a serious problem. Further-more the resistance of the thermo-couple must be a stable one.
The subject hall has often been used as an auditorium, while it was originally constructed as a gymnasium. But it was too reverberant and moreover suffered from remarkable multiple echoes due to the acoustically undesired shape. In this paper, the cause of origination of the multiple echoes is described, followed by the method of improvement of its acoustics and the results. The results of the filed measurement on the multiple echoes and the geometrical study on the travelling sound beams between the concave spherical shell ceiling and the flat floor showed as follows; (1) The time process of the observed multiple echoes was consistent with that concluded from the geometrical study, (2) That part of the ceiling where we looked up from the centre of the floor with an angle of elevation of above 30 degrees acted the leading role for the origination of the multiple echoes. In order to get rid of the multiple echoes and to get sufficient diffusion of sound, several hundreds of circular absorbers of three different sizes were suspended at random from that part of the ceiling in question. Further in order to decrease the reverberation time to optimum, plywood panels and rockwool with perforated facings were used on the remaining part of the ceiling. And the wavy canopies of plywood panel (reflecting board) were newly installed above the stage for the purpose of reinforcing speech and music heard at the seats. Thus, the multiple echoes became completely imperceptible and also the reverberation time became optimum. The complaints on the acoustics of the hall have ceased since the above reconstruction.
An approximate theoretical calculation is performed in obtaining the ultrasonic field near the circular plane source, vibrating with uniform normal velocity. As shown by Schoch, the Reyleigh surface integral giving the field reduces to a line integral when the coordinates are suitably chosen. By employing a simple approximation in calculating the above integral, it is shown that the pressure amplitude at the observed point is given as the sum of two terms, besides the constant term. Each of them, varying simply with the observed position, consists of the product of the so-called 'phase factor' and the 'amplitude factor'. Both factors given above can be easily obtained by a simple numerical calculation and the distribution figures of the values of them are shown for the near filed. The results obtained are in reasonable agreement with the author's experimental data for a 6. 9 mc quartz crystal described in his previous paper.