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of ambient noise at the lower audio frequencies has been suggested by C. J. Loda 

 of the Underwater Sound Laboratory. This system consists of three pairs of 

 equally spaced hydrophones placed along three mutually perpendicular axes (with 

 proper isolation this can be done with four hydrophones rather than six). Each 

 pair is connected in phase opposition so that three mutually perpendicular figure 

 eight patterns are formed. By simultaneous comparison of the signals from the 

 three pairs of hydrophones, information relative to directional distribution with- 

 in the noise field may be obtained. 



The spacing of the hydrophones in each pair is limited to that represent- 

 ed by one-half wavelength at the highest frequency to be used. The lowest us- 

 able frequency will be determined by the sensitivity of the hydrophone pair and 

 the receiver noise. Amplification before combination of hydrophone pairs will 

 be necessary if this scheme is to be used when the spacing is very small com- 

 pared to a half wavelength atthe frequency in question. 



The Underwater Sound Laboratory has been engaged for a number of 

 years in the collection of underwater sound propagation data, including measure- 

 ments of reverberation and ambient noise. In order to handle expeditiously the 

 large volume of data being accumulated, it was decided to establish a small IBM 

 calculating unit. While this hardly falls in the realm of underwater sound in- 

 strumentation for oceanographic research, the IBM equipment is a tool which 

 has permitted the study of problems which we would not otherwise have consid- 

 ered. In addition to providing a versatile facility for rapid analysis, the IBM 

 installation insures the orderly storage of basic data in a form useful to future 

 investigators. 



. Having once established such a computing facility, we have found it de- 

 sirable to give attention to the manner in which data are collected so that they 

 may be most efficiently processed by the machines. Where meter readings are 

 made in the field, the data are recorded on mark sensed IBM cards so that upon 

 return to the Laboratory the machines can immediately be put to work. How- 

 ever, for many applications, photographic film, paper recording tape, or mag- 

 netic tape are the most desirable medium for data collection. It was, there- 

 fore, necessary to provide for rapid reading and transcription of such records. 

 For this purpose the Underwater Sound Laboratory utilizes a Telereader* and 

 Telecorder. 



The Telereader is capable of handling either translucent or opaque rec- 

 ords with a maximum width of 12 inches and a minimum width determined by the 

 adequacy of the magnification of 2.5:1 for the record in question. It provides 

 means, for accurately measuring distance on the records along two orthogonal 

 axes, permitting rapid and convenient transmission of data from records to digi- 

 tal numbers representing deflections from an arbitrary fixed reference. It in- 

 corporates the necessary equipment for supporting and transporting the record; 

 for magnifying and projecting a section of the record, along with the measuring 

 cross wires, on a viewing screen; and for indicating the position of the cross 

 wires by mechanical counters. The Telecorder, in conjunction with an IBM 

 Summary Punch, permits recording of the cross wire positions in standard IBM 

 cards. 



The combination of Telereader, Telecorder, and Summary Punch is 

 capable of punching IBM cards at a maximum rate of 50 per minute. With this 

 combination the reproducibility of the measuring system of the Telereader is 



* - Manufactured by the Telecomputing Corporation, 133 E. Santa Anita 

 Avenue, Burbank, California. 



