. Basic methods for the calibration of sonar equipment. BAFFLES 163 180'. 270" = ?ioo bJ r R= CM 1 â â rH m fri d: Oj 10 â¢- R= CM â1â1â1â z _. â1 A^ = Dtnn9 S. I: 1 *" o ^ tc fel m Q 1 i ^ A ^ -R= CM z ^ t ^ * tâ o f \ / \ ^ y \ k \ 5 p / h= \ ^ u k= -^ ^ > \ \, / \ . \ .01 \ \ D 0 ?. 0 3 0 40 50 Figure 7. Chaiij^c in response of dome-enclosed trans ducer due to inteiposition ol l)alfle. KC RH 8. Attenuation \ersus lrcqiicnc% for different si/ed bubbles. {R = bubble radius.) Few ha\ c been inadc on the effect of a baffle on the rear respo
. Basic methods for the calibration of sonar equipment. BAFFLES 163 180'. 270" = ?ioo bJ r R= CM 1 â â rH m fri d: Oj 10 â¢- R= CM â1â1â1â z _. â1 A^ = Dtnn9 S. I: 1 *" o ^ tc fel m Q 1 i ^ A ^ -R= CM z ^ t ^ * tâ o f \ / \ ^ y \ k \ 5 p / h= \ ^ u k= -^ ^ > \ \, / \ . \ .01 \ \ D 0 ?. 0 3 0 40 50 Figure 7. Chaiij^c in response of dome-enclosed trans ducer due to inteiposition ol l)alfle. KC RH 8. Attenuation \ersus lrcqiicnc% for different si/ed bubbles. {R = bubble radius.) Few ha\ c been inadc on the effect of a baffle on the rear response of a transducer, ])articu- larly for transducers eiulosed in domes. Figure 7 shows the residts of one sucli measurement. Referring to tliis figure it is seen tliat for angles between the transcfucer and dome axes \arying from 90-270 de- grees (180 degrees corresponds to tire transchicer lac- ing away from the source) a '^4x24-inch rectangular and dome-enclosed baffle gives an average decrease of only a few decibels in the response of a dome-enclosed transducer 20 inches away compared to the response of a bare projector at the saine distance with no baffle interposed. These measurements, however, aLso in- clude the detrimental effect of reflections from the dome wall which usually increase the response in the 90 to 270-degree sector by 5-15 db. Thus, in this case, the effect of the baffle more or less cancels that of the dome. Further experiments are particularly desired which will compare the rear response (angles of 90- 270 degrees) of dome-enclosed and of bare transducers with and without a baffle. Sunnning up, it has been shown that the diffraction of sound around, rather than its transmission through, the baffle limits llie hitler's effectiveness. Roth witli regard to transmission loss and to diffiadion, air- lilled baffles are superior to steel. l"o minimize the dif- fraction effect, the baffle sliould be appreciably larger than the transducer and should
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