from the face of the transducer to the
point in the sound field where the signal ... indicated by the focal length ptf
point target focus for a ptf focus the lens ... focal length and the focal target
point or flat surface need to be specified ... 6 times the near field length and for a
point target focus ptf the maximum practical ... that the actual maximum response
point from a given target may not correspond ... increase in sensitivity at the focal
point as a practical matter there may be no ... shift the location of the y0
point toward the transducer face the end ...