. Basic methods for the calibration of sonar equipment. EQUIPMENT AT MOUNTAIN LAKES 115. Figure 19. AjJijlicalioii ol high-fieqiiciuy s\5tciu in Icsting scale model submarine in oiittlooi itsl aica. urenients of the reflection coefficient of such models will give a value for the reflection coefficient of the actual target. As the dimensions of the target and the wave length of the sound in actual operations are both reduced in the same ratio, all the reflection and diffraction of sound from the scale model and from the actual craft will occm- in exactly the same manner. Figure 49 shows a scale
. Basic methods for the calibration of sonar equipment. EQUIPMENT AT MOUNTAIN LAKES 115. Figure 19. AjJijlicalioii ol high-fieqiiciuy s\5tciu in Icsting scale model submarine in oiittlooi itsl aica. urenients of the reflection coefficient of such models will give a value for the reflection coefficient of the actual target. As the dimensions of the target and the wave length of the sound in actual operations are both reduced in the same ratio, all the reflection and diffraction of sound from the scale model and from the actual craft will occm- in exactly the same manner. Figure 49 shows a scale model of a submarine with all linear dimensions reduced 60 to 1. Measurements of the reflection coefficient carried out at 1565 kc give the results which would be obtained for similar measiueinents on the actual object at 26 kc and dis- tances 60 times those used for the model. Sound re- flected from the model is measured by an adjacent hydrophone shielded fi om the direct radiation of the projector. As the model is placed at several distances from the projector and rotated around various axes of s)iiimetr\, measiueinents of the reflection coeffi- cient are obtained as finictions of the range and the aspect of the model relative to the projector. Low-Frequency Pressure System The low-frec[uency pressure s\stem at the Moun- tain Lakes laboratory covers 2 to 100 c and was evolved as a result of the increasing need for an ac- curate method of hydrophone calibration at these frequencies under controlled conditions of tempera- ture and pressure. The system was designed and con- structed by the Bell Telephone Laboratories, Inc., under NDRC contract.^'' Uses and Limitations The testing technique with this apparatus is inde- pendent of auxiliary hydrophone standards. The. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the origi
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