214 BELL SYSTEM TECHNICAL JOURNAL 



depends upon the frequency, the intensity and the overtone structure of the 

 sound wave transmitting the tone. Similar relations are also given which 

 show how the loudness and the quality depend upon these same three 

 physical characteristics of the sound wave. These relationships were de- 

 monstrated by using the new Tone Synthesizer. By means of this in- 

 strument one is able to imitate the quality, pitch and intensity of any musi- 

 cal tone and also to produce many combinations which are not now used in 

 music. 



The Sound Spectrograph.^ W. Koenig, H. K. Dunx, and L. Y. Lacy. 

 The sound spectrograph is a wave analyzer which produces a permanent 

 visual record showing the distribution of energy in both frequency and time. 

 This paper describes the operation of this device, and shows the mechanical 

 arrangements and the electrical circuits in a particular model. Some of 

 the problems encountered in this type of analysis are discussed, particularly 

 those arising from the necessity for handling and portraying a wide range of 

 component levels in a complex wave such as speech. Spectrograms are 

 shown for a wide variety of sounds, including voice sounds, animal and bird 

 sounds, music, frequency modulations, and miscellaneous familiar sounds. 



Geometrical Characterizations of Some Families of Dynamical Trajectories} 

 L. A. MacColl. a broad problem in differential geometry is that of 

 characterizing, by a set of geometrical properties, the family of curves which 

 is defined by a given system of differential equations, of a more or less 

 special form. The problem has been studied especially by Kasner and his 

 students, and characterizations have been obtained for various families of 

 curves which are of geometrical or physical importance. However, the 

 interesting problem of characterizing the family of trajectories of an electri- 

 fied particle moving in a static magnetic field does not seem to have been 

 considered heretofore. The present paper gives the principal results of a 

 study of this problem. 



Visible Speech Cathode-Ray Translator."^ R. R. Riesz and L. Schott. A 

 system has been developed whereby speech analysis patterns are made 

 continuously visible on the moving luminescent screen of a special cathode- 

 ray tube. The screen is a cylindrical band that rotates with the tube about 

 a vertical axis. The electron beam always excites the screen in the same 

 vertical plane. Because of the persistence of the screen phosphor and the 

 rotation of the tube, the impressed patterns are spread out along a horizon- 



^ Jour. Acous. Soc. Amer., July 1946. 



^ Amer. Math. Soc. Transactions, July 1946. 



' Jour. Acous. Soc. Amer., July 1946. 



