The strength and diffraction parameters, Φ and Λ, are of importance in understanding fluctuations in oceanic acoustic transmission. A method for calculating Φ and Λ is described. Floquet’s theorem is shown to be of use in the calculation of Λ for a range‐independent sound‐speed profile. The sensitivity of Λ and Φ to changes in the sound‐speed profile and the buoyancy‐frequency profile is investigated. It is shown that rays with large intensity tend to have small Φ and small Λ except very near caustics.