Method for converting an ambisonic signal of the first order into a spherical field which is constituted by a plurality of monochromatic progressive planar waves and which is based on a frequential representation of the ambisonic signal obtained after temporal windowing and time/frequency transformation, including, for each frequency among a plurality of frequencies: • the separation of the ambisonic signal into three components comprising: ∘ a first complex vector component A which corresponds to the mean acoustic intensity vector of the ambisonic signal, ∘ a second complex vector component B whose complex coefficient is equal to subtracting the pressure wave generated by the component A from the pressure component of the ambisonic signal and whose direction is modified in accordance with a random process, ∘ a third complex vector component C which corresponds to subtracting the pressure gradient generated by the component A from the pressure gradient of the ambisonic signal and whose phases are modified in accordance with a random process and each of the three axial components of which takes, as a direction, a vector which is derived from a random process; • the grouping of the first, second and third vector components A, B and C as a total vector and a total complex coefficient which describes the spherical field, characterised in that: ∘ the total complex coefficient is equal to the sum of the complex coefficients corresponding to the three components, ∘ the total vector is equal to the sum of the directions of the three components, weighted by the amplitude of the complex coefficients corresponding to the three components. • the separation of the ambisonic signal into three components comprising: ∘ a first complex vector component A which corresponds to the mean acoustic intensity vector of the ambisonic signal, ∘ a second complex vector component B whose complex coefficient is equal to subtracting the pressure wave generated by the component A from the pressure component of the ambisonic signal and whose direction is modified in accordance with a random process, ∘ a third complex vector component C which corresponds to subtracting the pressure gradient generated by the component A from the pressure gradient of the ambisonic signal and whose phases are modified in accordance with a random process and each of the three axial components of which takes, as a direction, a vector which is derived from a random process; ∘ a first complex vector component A which corresponds to the mean acoustic intensity vector of the ambisonic signal, ∘ a second complex vector component B whose complex coefficient is equal to subtracting the pressure wave generated by the component A from the pressure component of the ambisonic signal and whose direction is modified in accordance with a random process, ∘ a third complex vector component C which corresponds to subtracting the pressure gradient generated by the component A from the pressure gradient of the ambisonic signal and whose phases are modified in accordance with a random process and each of the three axial components of which takes, as a direction, a vector which is derived from a random process; • the grouping of the first, second and third vector components A, B and C as a total vector and a total complex coefficient which describes the spherical field, characterised in that: ∘ the total complex coefficient is equal to the sum of the complex coefficients corresponding to the three components, ∘ the total vector is equal to the sum of the directions of the three components, weighted by the amplitude of the complex coefficients corresponding to the three components. ∘ the total complex coefficient is equal to the sum of the complex coefficients corresponding to the three components, ∘ the total vector is equal to the sum of the directions of the three components, weighted by the amplitude of the complex coefficients corresponding to the three components.