The two different definitions of the "amount of information", due respectively to N. Wiener and to C. E. Shannon, apparently contradict each other. Although recently L. Brillouin clarified the interrelation between them by a very ingenious argument, there are still several ambiguous points which require further remarks. We intend to make the notion of the amount of information much clearer by extending his arguments and making more profound considerations of these points. In§1 two definitions are compared and a unified interpretation is given. It becomes clear that they are in fact equivalent, merely looking the same thing from different points of view. Both are equal to the decrease of entropy during the process of extracting the message:I=-ΔS. In§2 the Brillouin's argument is somewhat extended, introducing the notion of the noise of the first kind. Ordinary noise, which is called here that of the second kind, is introduced in §3. With due definitions of "message entropy" and "noise entropy", the interpretation made in §1 is found to be not only still valid but able to claim the most generality. Misinterpretations about Shannon's theory can be avoided by introducing these notions of different kinds of entropy. In§4 the relationship between our entropies and those which appear in Brillouin's arguments is discussed, with some miscellaneous remarks.
The normal modes of vibration of 10 violin bodies have been studied with the resonance method. Excepting a few modes, most modes of vibration are different for each violin. From the vibrational figures it is shown that:1)one of the nodal lines of every modes of vibration passes by the neighbourhood of the sound-post. 2)the ends of the nodal lines on the front board correspond just to the ends of the nodal lines on the back board. 3)according to the observation of phase shift on the both sides of a nodal line, the violin body vibrates as a plate near the edge of the boards, and as a drum at the inner parts of the boards.
The auther deviced a new method of measuring the ultrasonic field intensity, using a small sonde (adout 2mm in diameter)consisted of a thermistor and sound absorbing material. By this method the transmitted waves(450KC and 1000KC)through thin plates were measured at various angles of incidence. The measurements were performed also on curved surfaces. The results give informations on designing vessels for ultrasonic applications.
The transmission of a plane acoustic wave at oblique incidence through a stratified solid medium is studied theoretically. The matrix method is used following Thomson, but the three errors in his paper are corrected. And some special cases are considered.
(A)The ultrasonic velocities and elastic constants of linear polymers were measured by Bar-Walti's rotating plate method with impulse ultrasonic waves. (B)The linear polymers used are polystyrene, polymethyl-methacrylate, polyamide(Amilan), polyvinyl-acetate, and polyvinyl-chloride. (C)The frequencies from 450 kc. to 8Mc. /sec. were used. (D)No difference of elastic constants was found with polyvinyl-acetates of different polymerisation degrees from 6700 to 1150. (E)Elastic constants decrease with increasing plasticiser contents in the following systems:polyvinyl-acetate with dibutly-phthalate, and polyvinyl-chloride with dioctyl-phthalate.