The dynamic characteristics of RMS indicators incorporated in sound level meters, noise voltmeters, etc. are discussed. First, the relationship among specifications for dynamic characteristics, mechanical constants used for design, and meter readings were investigated. The indicator characteristics can be given by threedimensional graphical presentation, and their tolerance limits can be given as some threedimensional shape. As a result, the relationship between various characteristics of the indicator can easily be studied. Finally, specifications on the design of indicators became reasonably possible from the viewpoint of indicated errors.
Hitherto diaphragms of electroacoustic transducers were made by press method, and by which high precision can be obtained as is well known. On the other hand, in the course of designing acoustical apparatus, it is often necessary to make various types of diaphragms for testing. In such cases, as required number of each type is not so many, the press method is inconvenient for this purpose because of the cost of making press moulds, and electroforming method is considered to be far better than this method. In this paper, application of electroforming to diaphragms and results of some experiments are described. Copper is used as material. Effect of deposition on thickness and structure of metal plate are studied. Density, Young's modulus and tensile strength are also examined. Displacement-frequency characteristics of electroformed diaphragms are satisfactory and similar to those of diaphragms made by usual method.