The frequency spectrum of log‐amplitude fluctuations is substantially modified (flattened) by a previously neglected effect: the vertical advection of short internal waves by the more energetic internal waves with large vertical wavelength. The log‐amplitude spectrum is sensitive to this vertical advection and to curvature of the equilibrium sound ray, whereas the phase spectrum is not. Noninternal‐wave ’’frozen’’ finestructure contributes to the log‐amplitude frequency spectrum through vertical advection, but not to the phase spectrum. The Cobb Seamount experiment is treated as an example; the spectrum of the modified theory agrees well with observations except at high frequency ( near the buoyancy frequency ).