The present technology is directed to methods for characterizing nonlinear ultrasound fields and associated systems and devices. In several embodiments, for example, a method of calculating output of a high intensity focused ultrasound (HIFU) device comprises treating a target site with a multi-element HIFU array. In some embodiments, the array comprises a generally spherical segment. The method can further include simulating a field of the array by setting a boundary condition for the array. The boundary condition can be set by simplifying at least one geometrical aspect of the generally spherical segment.