494 BELL SYSTEM TECHNICAL JOURNAL 



the means chosen for reproduction in residences would differ materially 

 from those used in large ballrooms or in the presentation of synchro- 

 nized motion pictures. 



Beforp considering the methods and results referred to in the title 

 of this paper, it may be well to make a rough division of the problem. 

 The storing or recording of sound requires, first, a mechanical system 

 which will respond faithfully to the sound waves which are to be re- 

 corded. Then, there is required some material in or on which this 

 sound may be recorded and an intervening system which permits the 

 sound waves to make the record in this material. In the usual case, 

 and in that with which we are particularly concerned here, there is a 

 mechanical system which will vibrate in response to the sound which 

 is to be recorded and directly through some mechanical linkage or less 

 directly through an electrical linkage, drive a cutting mechanism which 

 will impress a wax record. 



The first consideration, therefore, is the character of the sound which 

 is to be recorded including all of the effects of reverberation and the 

 general questions of studio design. Next to be considered is the man- 

 ner in which the cutting instrument shall impress this speech or musical 

 record upon the constantly rotating wax disk, which disk is commonly 

 called the wax master. In this connection, there will be discussed also 

 the relative value of the electrical and mechanical linking of the cutting 

 knife with the mechanism which receives the sound waves. Following 

 the discussion of these problems and a brief reference to the state of the 

 prior art, there remains to be considered the reproduction of the sound 

 which is stored in the cuts or grooves of the wax record. 



In the case of reproduction also, there is required a mechanical sys- 

 tem which will respond to these cuts in the wax and a system which will 

 set up in the air-sound waves essentially identical to those picked up 

 by the first mechanism of the recording system. Between these two 

 systems, a mechanical linkage intervenes in the case under discussion, 

 but reference is made to the relative advantages of this system com- 

 pared with the use of an electrical linkage. 



First to be described, is the character of the sound which is to be 

 recorded and reproduced and the effects of reverberation and transients 

 upon the listener's sensation of this sound. 



Studio Characteristics and Transients 



Phonographic reproduction may be termed perfect when the com- 

 ponents of the reproduced sound reaching the ears of the actual listener 

 have the same relative intensity and phase relation as the sound reach- 



