Device for the representation, in a frequency-wave number reference frame f-k, of the propagation of an ultrasound wave in a dihedral guide (1), which comprises ultrasound emitters (2) referenced by “Ej” with j an integer varying between 1 and N, N a strictly positive integer and ultrasound receivers (3) referenced by “Ri” with i an integer varying between 1 and M, M a strictly positive integer, the receivers being disposed spatially over a first segment of a straight line according to a regular pitch “A”, which comprises means for processing the signal received by the receivers, originating from the emitters, and in which the processing means comprise means for calculating a modified discrete spatial Fourier transform, for a spatial integration variable “x”, centered in the middle of said first segment and running through the receivers in the direction of increasing x, and for a wave vector k(x) equal to a product k.P(x), with k a constant coefficient in x and included between 0 and 2*Pi/A, and with P(x) a polynomial in x, of coefficient of degree 0 in x equal to 1 and of coefficient “C” of degree 1 in x such that C.A lies between − 1/10 and + 1/10
