Abstract: 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.

Abstract: 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.

Abstract: A probe including NE ultrasonic emitters and NR ultrasonic receivers is applied on the medium to be characterized. Each emitter is activated successively and each time signals are detected on the set of receivers during a time window. Each of the NE×NR signals detected is converted by temporal Fourier transformation to a sum of vibrational components each having its temporal frequency. For each frequency, a matrix NE×NR of complex amplitudes of vibrational components having this frequency is extracted. These matrices are decomposed into singular values, the smallest are eliminated, and the singular vectors associated with the singular values retained, a base of the space of the reception signals is formed, for each frequency. The contribution of each plane wave, characterized by its velocity, in this base is calculated. This contribution is represented in the form of a grey level in a frequency-propagation velocity reference system.

Abstract: A probe including NE ultrasonic emitters and NR ultrasonic receivers is applied on the medium to be characterized. Each emitter is activated successively and each time signals are detected on the set of receivers during a time window. Each of the NE×NR signals detected is converted by temporal Fourier transformation to a sum of vibrational components each having its temporal frequency. For each frequency, a matrix NE×NR of complex amplitudes of vibrational components having this frequency is extracted. These matrices are decomposed into singular values, the smallest are eliminated, and the singular vectors associated with the singular values retained, a base of the space of the reception signals is formed, for each frequency. The contribution of each plane wave, characterized by its velocity, in this base is calculated. This contribution is represented in the form of a grey level in a frequency-propagation velocity reference system.