A method for searching for a defect likely to affect a rotating mechanical power transmission device, said mechanical device being an aircraft gear comprising two toothed wheels, the method comprising: - a step of obtaining a signal s which can be modeled by a product of a high-frequency signal s1 and of a low-frequency signal s2, generated by the rotating mechanical power transmission device and acquired by a sensor; - a step of determining estimates of the signals s1 and s2 minimizing a difference between all or part of the signal s and a product of these estimates, said determination step comprising: ∘ a step of re-sampling a sequence derived from the signal s of a duration equal to an analysis duration, said analysis duration being a integer multiple of a period of the low-frequency signal s2, said sequence derived from the signal s being re-sampled with a regular pitch equal to a fraction of the analysis duration; ∘ a step of obtaining a discrete Fourier transform of the re-sampled sequence, said discrete Fourier transform comprising a plurality of harmonics; ∘ a step of constructing a matrix M from the discrete Fourier transform obtained, the dimensions of the matrix depending on a number of harmonics determined for the signal s1 and on a number d harmonics determined for the signal s2, each component of the matrix comprising an amplitude of a harmonic of the discrete Fourier transform obtained; ∘ a step of performing a rank 1 approximation of the matrix M and obtaining discrete Fourier transforms of the estimates of the signals s1 and s2; - a step of analyzing the estimates of the signals s1 and s2 with a view to detecting the presence of a defect affecting the rotating mechanical power transmission device; - if a defect is detected at the end of the analysis step, a step of locating said defect from the at least one of the estimates of the signals s1 and s2. - a step of obtaining a signal s which can be modeled by a product of a high-frequency signal s1 and of a low-frequency signal s2, generated by the rotating mechanical power transmission device and acquired by a sensor; - a step of determining estimates of the signals s1 and s2 minimizing a difference between all or part of the signal s and a product of these estimates, said determination step comprising: ∘ a step of re-sampling a sequence derived from the signal s of a duration equal to an analysis duration, said analysis duration being a integer multiple of a period of the low-frequency signal s2, said sequence derived from the signal s being re-sampled with a regular pitch equal to a fraction of the analysis duration; ∘ a step of obtaining a discrete Fourier transform of the re-sampled sequence, said discrete Fourier transform comprising a plurality of harmonics; ∘ a step of constructing a matrix M from the discrete Fourier transform obtained, the dimensions of the matrix depending on a number of harmonics determined for the signal s1 and on a number d harmonics determined for the signal s2, each component of the matrix comprising an amplitude of a harmonic of the discrete Fourier transform obtained; ∘ a step of performing a rank 1 approximation of the matrix M and obtaining discrete Fourier transforms of the estimates of the signals s1 and s2; ∘ a step of re-sampling a sequence derived from the signal s of a duration equal to an analysis duration, said analysis duration being a integer multiple of a period of the low-frequency signal s2, said sequence derived from the signal s being re-sampled with a regular pitch equal to a fraction of the analysis duration; ∘ a step of obtaining a discrete Fourier transform of the re-sampled sequence, said discrete Fourier transform comprising a plurality of harmonics; ∘ a step of constructing a matrix M from the discrete Fourier transform obtained, the dimensions of the matrix depending on a number of harmonics determined for the signal s1 and on a number d harmonics determined for the signal s2, each component of the matrix comprising an amplitude of a harmonic of the discrete Fourier transform obtained; ∘ a step of performing a rank 1 approximation of the matrix M and obtaining discrete Fourier transforms of the estimates of the signals s1 and s2; - a step of analyzing the estimates of the signals s1 and s2 with a view to detecting the presence of a defect affecting the rotating mechanical power transmission device; - if a defect is detected at the end of the analysis step, a step of locating said defect from the at least one of the estimates of the signals s1 and s2.