362 BELL SYSTEM TECHNICAL JOURNAL 



chanical or optical translating mechanism for translating the 24-frame film 

 picture into a 30-frame interlaced television picture. In the present equip- 

 ment it was found more expedient to simplify the construction by allowing 

 the use of specially printed film. Ordinary 24-frame film is "stretched" by 

 printing every other frame twice and the remaining frames three times in 

 succession, thereby producing a film with a total of 60 frames instead of the 

 original 24. Vertical scanning is then obtained by the continuous motion of 

 this film at the rate of 60 frames per second and horizontal scanning by a 

 simple electronic line sweep in the dissector tube. 



Acoustic Design Features of Studio Stages, Monitor Rooms, and Review 

 Rooms.^ D. P. LoYE. A survey was made of studio experience, and meas- 

 urements were made of stages, review rooms, and other units. These data 

 were correlated and used as a valuable guide in the determination of the 

 optimum characteristics and dimensions recommended for major studio 

 scoring stages, monitor rooms, dubbing rooms, review rooms, and studio 

 theaters. 



Information regarding Hollywood preview tlieaters is included in an 

 Appendix. 



A New Microphone Providing Uniform Directivity over an Extended Fre- 

 quency Range? R. N. Marshall and W. R. Harry. A new microphone 

 is described which consists of a moving coil pressure element combined with 

 an improved ribbon pressure gradient element to give a cardioid directional 

 characteristic. The theory of operation is reviewed, and consideration is 

 then given to variations in directivity caused by diffraction, separation of 

 the elements, and disparities in their phase and response characteristics. 

 It is then shown how these variations are largely eliminated by equalization 

 in the electrical circuit so tliat the resulting directivity is practically in- 

 dependent of frequency throughout the range from 70 to 8000 cycles. The 

 use of a moving coil pressure element makes high efficiency possible, while 

 the design of an unusually rugged ribbon element provides a marked reduc- 

 tion in noise due to air currents. Several useful directional patterns in 

 addition to the cardioid pattern are provided in the new microphone, and 

 the theory and merits of these patterns are presented. Finally some of the 

 results which were obtained in field trials of the new microphone are dis- 

 cussed. 



The Magnetostriction, Young's Modulus and Damping of 68 Permalloy as 

 Dependent on Magnetization and Heat Treatment.^ H. J. Williams, R. M. 



^ Jour. Soc. of Motion Picture Engineers, June 1941. 

 ''Jour. Acous. Soc. Anier., April 1941. 

 ^Fhys. Rev., June 15, 1941. 



