An experiment was performed to investigate the noncollinear interaction of a high‐frequency tone with low‐frequency noise. The nonlinear interaction took place in an air‐filled rectangular duct. A low‐frequency band of noise was transmitted in the (0,0) mode together with a high‐frequency tone in the (1,0) mode. The angle between the two interacting waves was 55°. Measurements of the frequency spectra were made at locations that were well within the shock formation distance of either primary wave. The spectral shapes of the sum and difference frequency sidebands of noise are scalloped in appearance, and the number of nulls in each sideband increases with range from the source. Theoretical predictions for the nonlinearly generated sidebands are in good overall agreement with experiment. The predictions are based on a quasilinear analysis developed previously to describe the noncollinear interaction of two tones in a rectangular duct [M. F. Hamilton and J. A. TenCate, J. Acoust. Soc. Am.81, 1703–1712 (1987)]. Comparisons are made with the corresponding case of collinear interaction, in which both primary waves propagate in the (0,0) mode.