ABSTRACTS OF TECHNICAL ARTICLES 421 



Direct Recording and Reproducing Materials for Disk Recording} 

 A. C. Keller. Recently materials for direct recording and repro- 

 ducing work have been improved so that they are now suitable for 

 many uses. These materials, as they are available on the market, 

 are classified chemically into five groups and measurements are given 

 of frequency characteristic, surface noise, life, distortion, etc. These 

 data have been taken with both lateral and vertical recording, 



^ Jour. Acous. Soc. Amer., April 1937. 



