Tom turkeys usually gobble when they are not with, or have not been with, thehens. Gobbling usually peaks when the toms are not with hens, but want to be with them. Then when they are with the hens, they switch to strutting, spitting and drumming to attract the hens. Once most of the hens have nested, the toms start gobbling again, because they still want to breed, but the hens don't , because they are on the nest.

Rainy or windy days also reduce gobbling.

Itcould bethe weather, or the toms may be between gobbling peaks, or the tomsare not in your "hearing" area, or they just don't feel like gobbling.

Check out these Gobbling Activity Graphs, they might help you understand - http://www.trmichels.com/TurkeyActivityGraphs.htm.