M. P. Fodch 117 
4, 
5. 
Fig. 6.15. Sectional 
drawing of the barge. 
Primary reciprocity calibration by sine wave or in a narrow band. 
Secondary calibration by sine wave by comparison with a standard pro- 
jector. 
Calibration and recording of directivity patterns of transducers larger 
than the wavelength where the dimensions of the anechoic tank do not 
allow working out of the Fresnel zone. 
Calibration of small transducers where surface reflection due to the small 
value of the directivity could not be avoided in an anechoic tank. 
Study and tests of sonar domes. 
6.3.2, Physical Features and Layout 
A pit 30 m long, 15 m wide, and 4.5 m deep has been dredged in the harbor 
bottom of Le Brusc, and the testing barge, shown in Figs. 6.14 and 6.15, has 
been moored over it 200 m off shore. This barge has been converted into a test 
facility by the installation of two test wells permitting a maximum separation 
distance from projector to receiver of 6.5 m. The barge has an over-all length 
of 19.10 m and a width of 7.2 m. It has a glass-walled structure covered with a 
roof, and is divided into calibrating, measuring, and office rooms. For hoisting 
the transducers and lowering them into the well, there is a monorail carrying a 
hoist with a weight-handling capacity of 1.5 tons. 
The wells are surrounded by a gliding rail for measuring instruments. A 
bridge is mounted across carrying a rolling carriage and a shaft which rotates 
by remote control, while a polar ink recorder driven by a servosystem records 
the directivity patterns. By means of this carriage, transducers of up to 1.5 tons 
can be displaced in all directions, the bearing being adjustable to 14°, while the 
separation distance between the two shafts is known with an accuracy of 5 mm. 
Less weighty transducers (up to 300 kg) and projectors to be tested are displayed 
by two smaller carriages. 
Another rolling carriage gliding on a rail fixed below the keel of the barge 
carries transducers for continuous measurement of the acoustic field between 0 
