Determination of the coordinates of the annular cross section experiencing maximum pressure in the acoustic field of a transducer

It is often desirable to find out the spatial positions on a virtual annular disc where ultrasonic pressure from a flat unfocussed piston-type transducer would be maximum in comparison with other annular discs in the acoustic field. For example, in many applications it is required to transmit sound waves in the axial direction through the wall of a cylindrical metal pipe. It is difficult to get efficient transmission of sound energy through a pipe with a flat transducer because only a limited portion is in contact with the transducer face. Moreover, sound pressure within the near field varies along the axial direction as well as the off-axial direction. In this paper, various conditions are evaluated with a view to finding out an easy method for maximum transmission of sound through pipe material in its axial direction. Theoretical expressions are formulated for points of maximum acoustic pressure on an annular disc. These have been validated experimentally.