320 BELL SYSTEM TECHNICAL JOURNAL 



The Rapid Record Oscillograph in Sound Picture Studies.* A. M. 

 Curtis, T. E. Shea, and C. H. Rumpel. This paper describes a 

 special oscillograph which was designed for making rapid records in 

 sound picture studies. The oscillograph is briefly described, and 

 illustrations are presented of records obtained in making the following 

 studies: microphonic action of vacuum tubes; noise levels in amplifiers; 

 investigations on rectifiers; studies on light valve clash; action of the 

 biasing current of light valves as used in noiseless recording by the 

 variable density method; acoustical studies showing the rise and 

 decay of transients ; loud speaker selection with regard to load carrying 

 capacity and mechanical flutter investigations of reproducer sets. 



Vertical Sound Records — Recent Fundamental Advances in Mechanical 

 Records on " Wax." ^ H. A. Frederick. This paper describes recent 

 progress which has been made in laboratory studies of mechanical 

 records of sound cut on a wax disk. Both theoretical and experi- 

 mental investigations indicate that a phonograph record, cut with 

 vertical undulations instead of the more usual lateral undulations 

 possesses fundamental advantages. The principal improvement 

 comes from a marked increase in the volume and frequency range over 

 which faithful reproduction may be obtained. A higher volume level 

 can be recorded for the same groove spacing and speed. More playing 

 time can be provided with a given size of record and volume level since, 

 for these conditions, both the groove spacing and speed may be re- 

 duced. Improvements in methods of processing the stampers and in 

 the record material give a large reduction in surface noise and hence a 

 corresponding increase in the volume range. With these improve- 

 ments the frequency range which can be reproduced satisfactorily can 

 be extended nearly an octave to 8000 to 10,000 cycles. Other improve- 

 ments incidental to the improvements noted above are great improve- 

 ment in the quality of reproduction obtainable directly from a soft 

 "wax" record and a great extension in the life of the hard record. 



Effect of Shore Station Location Upon Signals.^ R. A. Heising. 

 Experiments are described for ascertaining the attenuation suff^ered 

 by the unreflected wave in traversing relatively small amounts of land 

 between the seashore and hypothetical inland sites. The results 

 show 8 to 12 db attenuation for 1 mile inland with greater attenuation 

 thereafter for unfavorable terrain. Swampy ground produces small 

 attenuation. The classical theory of wave transmission past a straight 



* Jour. S. M. P. E., January, 1932. 

 6 Jour. S. M. P. E., February, 1932. 

 ^Proc. I. R. E., January, 1932. 



