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1954-55 Theatre Catalog, 12th Edition, Page 277 (241)

1954-55 Theatre Catalog, 12th Edition
1954-55 Theatre Catalog
1954-55 Theatre Catalog, 12th Edition, Page 277
Page 277

1954-55 Theatre Catalog, 12th Edition, Page 277

Basic Principles of Stereophonic Sound*

An Important and Fundamental Study of the Principles of Stereophonic Sound is Offered by A Leading Sound Expert

BRIEF: Stereophonic sound has become of vital importance to the industry. The subject has been studied for many years . . . but the published material is scattered . . . This paper summarizes the fundamental theory underlying stereophonic sound so far as it has been published . . . and gives examples of how the theory is employed in representative practical situations . . . Fundamental differences between ordinary binaural listening and stereophony are pointed out . . . as well as similarities . . . It is shown that much qualitative but little quantitative information has been reported . . . Factors which aid some stereophonic effects are shown to be detrimental to others . . . aml methods of minimizing the undersirable conditions are suggested.


In 1941 K. de Boer wrote: thhen the time comes to make use of stereophonic reproduction in the cinema, in broadcasting, etc., and the opinion becomes more and more general that the improvement in quality so obtained is worth the trouble, it will become necessary in

HMO]! of My] article appeared a; a paper in the November, 1953 itmr of {be Jam/ml of the Sour/y of Motion P/t'lnre and Tflft'lJ'i071 Engincrrr, and ii promoted with the [Jazmin/'01: of the SMPTE.

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Sound Consultant

the first place to find a process of making. stereophonic records on a large scale." Although even at that time stereophonic reproduction was far from new, de Boer's enthusiasm for ttmaking an orchestra plastically audiblell was shared by only a few. Now the time he forecast has finally come. Stereophonic sound has suddenly become of vital concern to the motion picture and sound recording industries, with multiplechannel recording the order of the day.

Stereophonic reproduction brings a truly remarkable increase in the realism of the sound and in the pleasure of listening to it. In one attempt to measure this quantitatively, reported by Fletcher, the observers listened alternately to singleschannel and stereophonic reproduction. In the stereophonic channels low-pass filters were inserted, while the single channel was maintained flat to 15 kc. Half of the observers still preferred stereophonic reproductions when the low-pass cutoff was reduced to about 5 kc. However, this paper is concerned primarily with the mechanism of stereophonic sound rather than its advantages, which are now so well recognized.

DEFINITIONS As in most new developments, differences in nomenclature have arisen

which tend to obscure precise descriptions of systems. The words tibinauralli and ustereophonic" are those most frequently used, but not with uniform meanings. This is not a new phenomenon. Alexander Graham Bell writing in 1880 referred to the "stereophonic phenomena of binaural audition," in describing experiments on the directional sense' in hearing conducted with his newly invented telephone. The following definitions apply to the discussions of this paper, and are limited to electroacoustic sound reproducing systems:

Binaural-A system employing two microphones, preferably in an artificial head, two independent amplifying channels, and two independent headphones for each observer. This duplicates normal listening,

Stereophonic a A system employing two or more microphones spaced in front of a pickup area, connected by independent amplifying channel to two or more loudspeakers spaced in front of a listening area. This creates the illusion

THE ORIGINAL two channel slereophonic sound system is shown in the foyer ol Philadelphia Academy of Music back in the year 1932.
1954-55 Theatre Catalog, 12th Edition, Page 277