Using a microbarograph at Brisbane, Australia, ground-level atmospheric gravity waves (GL-AGWs) have been detected during three sunspot-minimum (Rz-min) periods (1971-1977; 1983-1987 and 1992-1997). Analyses have produced results similar to those found earlier for the Rz-min period 1963-1966. Some of the GL-AGWs (around 25%), which occur one-or two days before cold-front passages at Brisbane, are recorded statistically on the same day, as the low-pressure centres responsible for these fronts pass the Brisbane longitudinal meridian. As before (for 1963-1966), delays by several days after enhanced activity are found using (i) the geomagnetic H component for the periods 1971-1977 and 1983-1987 and (ii) the Kp sum for the other period (1992-1997) for which H-component data were unavailable. Also, AU-indices were used for the 1983-87 period. During 22 years embraced by the four periods there were 619 frontal passages at Brisbane, 40% of which were associated with GL-AGWs. If, similar to auroral-zone events, D-region absorption spike events occur in sub-auroral regions, it is suggested that burst precipitation events of this kind may be responsible for the generation of GL-AGWs.