The most familiar application of an #AWS is a #welltest down the annulus (casing) to determine the liquid level depth by counting tubing collars. Jointed tubing sections are screwed together with a collar which is an obstruction (thicker than the tubing). A small portion of the sound wave is thus reflected to surface at every collar, causing collar kicks.
Sonic surveys can also be conducted down casing only (no tubing installed) and down jointed tubing. The joints in these cases are expansions (i.e. slightly larger than the pipe) thus their kick is opposite to the first kick (explosion or implosion). Sometimes, however, the kicks are too faint for accurate interpretation. When this happens use the acoustic velocity method.
To estimate a tubing-side shot with faint kicks, one can line up the annular shot with good collar kicks alongside the tubing shot (from the same well, of course).