Method of determining impulse responses from a medium in relation to the transmission of waves between different points

Procedure for determining impulse responses of a medium (2) with respect to the transmission of waves between different points (T1-TN), method comprising: (a) at least one step of emission in the course of which waves are emitted in means (2) generating signals ei (t) from a number N of emission points (T1-TN) belonging to the medium, an integer at least equal to 2 i where N is an understood index between 1 and N which designates one of said N emission points, (b) at least one receiving step during which rj signals (t) are detected from said waves after transmission in said medium, at a number M of reception points (T1-TN) belonging to the medium, where M is a natural nonzero integer and j an integer between 1 and M index designating one of said M reception points, (c) and at least one step of determination of said impulse responses hij ( t) between each emission point i and each point ja reception from the signals emitted ei (t) and detected rj (t), characterized in that during step (a), the ei signals (t are emitted simultaneously) by said N emission points (T1-TN), taking these signals ei (t) a duration T and being each a sum of n elementary signals substantially monochromatic, of equal amplitude and of respective frequencies f 0, i + k. Af, where f 0, i own predetermined frequency point i, k is an integer between 0 and n, n an integer at least equal to 2 and Af a step predetermined frequency, being the f0 frequencies, i own respective of the different points i different and being included in a frequency band .DELTA.f width, and because in the course of step (c), each impulse response hij (t) is calculated from a correlation signal between ei signal (t ) issued at the point i and the signal rj (t) detected at point j.