. Basic methods for the calibration of sonar equipment. EQUIPMENT AT MOUNTAIN LAKES 101 Tablk I. Tesldiita required for dome investigation. PROJECTOR HYDROPHONE Purpose of Angular position* Arrange- ment in observation a e <j) = e â a Fig. 36 Transducer response 0° (A) without dome Transducer pattern IStiO" (A) without dome Transmission response f)° 0° (B) through nose of dome Transmission response l)'^ 180° (C) tlirougli rear of dome 1 ransducer pattern |:iGO° 180° (C) with l)affle and rear of dome iiucrposedt Transmission pattern 0° -[â .â iliO" (D) tliiougli tiomc \s ang
. Basic methods for the calibration of sonar equipment. EQUIPMENT AT MOUNTAIN LAKES 101 Tablk I. Tesldiita required for dome investigation. PROJECTOR HYDROPHONE Purpose of Angular position* Arrange- ment in observation a e <j) = e â a Fig. 36 Transducer response 0° (A) without dome Transducer pattern IStiO" (A) without dome Transmission response f)° 0° (B) through nose of dome Transmission response l)'^ 180° (C) tlirougli rear of dome 1 ransducer pattern |:iGO° 180° (C) with l)affle and rear of dome iiucrposedt Transmission pattern 0° -[â .â iliO" (D) tliiougli tiomc \s angular position 1 ransducer patterns -[â¢atjo" |360° 0° (E) through dome 15° 30° 45° etc., incl. known critical angles * Transducer used as a receiver oidy. t If the dome is equipped with a remo\able halllc, tests shoidd be matle with (a) tlomc and battle, (b) dome alone, and (c) bailie alone, to see how battle and dome attect noise pickiq) over a range of angles aboia the rear of the transducer. Studies of Acoustic IVar'e .S'/gnrt/ Generators of Complex Waves. Devices designed to generate acous- tic signals of complex wave iorms are divided into two major categories, each retinii ing a special testing technique. In general, the choice of technitjue is based on such factors as a continuous signal, recur- rent signal and ils rate, and the crest factor (ratio of peak to rms valtics). Obviously, the use of eleclroniechanical eipiip- ment for the recording of random events is limited by such factors as the speed and dynamic range of re- corder response. Signals that are intermittent, that have low recurrence rates, and those with crest factors greater than , are usually studied by means of a cathode-ray oscilloscope and high-speed oscillograms. Signals that are continuous or of high recurrence rate, with crest factors not exceeding , may be studied with the apparatus of system 2. The procedure for in- vestigating such signals with system 2
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