A. B. Wood 189 
shown by a horizontal midwater line of the scan record (a). The latter shows 
not only this, but the whole pattern of sound distribution between surface and 
bottom of the water layer. The stratified character of the transmitted beam 
and their relative intensities and angular spacings are clearly shown in the 
original scan records. Figure 10.29 shows a series of nine scan records, the 
first eight of which show sound fields in vertical sections across the tank at 
various ranges between 5 and 400 cm from a 2 cm-diameter barium titanate 
transmitter operating at a frequency of 568 kcps, the semiangle of beam in this 
case being 9.3°, approximately. The water depth was 2 in. and the bottom rubber - 
covered. The last (9th) record shows a scan picture along the axis of the pri- 
mary beam from one end of the tank range (5 to 400 cm) to the other. It is of 
interest to identify the transverse section scans at the corresponding ranges of 
the longitudinal scan. The eight transverse records show very clearly the spread- 
ing of the primary beam and its tendency to stratification in horizontal planes, 
varying in spacing between the layers according to range from the transmitter. 
While it is appreciated that the directional transmitters used in these experi- 
OIRECTIONAL TRANSMISSION. 
Sound Fields across the beam at various ranges (Recors 8) 
Scund Fields along the heam 5 to 4O0cms ronge (R, 5 
RANGE cms. 
20 
40 
Fig. 10.29. Sound fields across 
the beam of the directional 
projector at various ranges. 
Stems 100 200 700 600 
VERTICAL SESK ON AXIS OF PRIMARY SEAN 
