Method for determining active and reactive acoustic intensity of at least one sound source based on determination of acoustic impedance and mean square velocity of an acoustic particle, the method comprising the following steps: - directly measuring time signal of an acoustic pressure p(t) and an acoustic velocity v (t) = (vx(t), vy(t), vz(t)) produced by said at least one sound source and discretizing them as p(n), vx(n), vy(n), vz(n) respectively; - computing frequency spectra P̂ m ( ω n), V ^ x m ω n, V ^ y m ω n, V ^ z m ω n of the measured signals by Fast Fourier Transform; - calibrating the frequency spectra through suitable calibration functions K (ω) and Γ̂( ω) = (Γ̂ x ( ω),Γ̂ y ( ω),Γ̂ y ( ω)), according to equations: - computing a first complex vector impeidance Ẑ 1( ω n), having real spatial components R1 x,y,z (ω n) and imaginary spatial components X1 x,y,z (ω n), according to equations: - computing a second complex vector impedance Ẑ 2( ω n), having real spatial components R2 x,y,z (ω n) and imaginary spatial components X2 x,y,z (ω n), according to equations: - computing power spectra of velocity components: V x ^ 2 ω n = V ^ x V ^ x ∗ V ^ y 2 ω n = V ^ y V ^ y ∗ V ^ z 2 ω n = V ^ z V ^ z ∗ where V ^ x ∗, V ^ y ∗, V ^ z ∗ are complex conjugate spectra of the velocity components V̂ x,V̂ y, V̂ z; - computing a frequency distribution of a first active intensity I 1( ω n)according to equations: I → 1 ω n = R 1 x V ^ x 2 ω n, R 1 y V ^ y 2 ω n, R 1 z V ^ z 2 ω n - computing a frequency distribution of a second active intensity I ̅ 2 ω n _ according to equations: I → 2 ω n = R 2 x V ^ x 2 ω n, R 2 y V ^ y 2 ω n, R 2 z V ^ z 2 ω n; - determining an active acoustic intensity I ( ω n) and a first relative uncertainty ε i ( ω n):, with i=(x, y, z), according to following equations: - computing a frequency distribution of a first reactive intensity Q 1( ω n) according to equation: Q 1 ω n = X 1 x V ^ x 2 ω n 2 + X 1 y V ^ y 2 ω n 2 + X 1 z V ^ z 2 ω n 2; - computing a frequency distribution of a second reactive intensity Q 2( ω n) according to equation: Q 2 ω n = X 2 x V ^ x 2 ω n 2 + X 2 y V ^ y 2 ω n 2 + X 2 z V ^ z 2 ω n 2; - determining a reactive acoustic intensity Q ( ω n) and a second relative uncertainty ε a ( ω n), according to following equations: - directly measuring time signal of an acoustic pressure p(t) and an acoustic velocity v (t) = (vx(t), vy(t), vz(t)) produced by said at least one sound source and discretizing them as p(n), vx(n), vy(n), vz(n) respectively; - computing frequency spectra P̂ m ( ω n), V ^ x m ω n, V ^ y m ω n, V ^ z m ω n of the measured signals by Fast Fourier Transform; - calibrating the frequency spectra through suitable calibration functions K (ω) and Γ̂( ω) = (Γ̂ x ( ω),Γ̂ y ( ω),Γ̂ y ( ω)), according to equations: - computing a first complex vector impeidance Ẑ 1( ω n), having real spatial components R1 x,y,z (ω n) and imaginary spatial components X1 x,y,z (ω n), according to equations: - computing a second complex vector impedance Ẑ 2( ω n), having real spatial components R2 x,y,z (ω n) and imaginary spatial components X2 x,y,z (ω n), according to equations: - computing power spectra of velocity components: V x ^ 2 ω n = V ^ x V ^ x ∗ V ^ y 2 ω n = V ^ y V ^ y ∗ V ^ z 2 ω n = V ^ z V ^ z ∗ where V ^ x ∗, V ^ y ∗, V ^ z ∗ are complex conjugate spectra of the velocity components V̂ x,V̂ y, V̂ z; - computing a frequency distribution of a first active intensity I 1( ω n)according to equations: I → 1 ω n = R 1 x V ^ x 2 ω n, R 1 y V ^ y 2 ω n, R 1 z V ^ z 2 ω n - computing a frequency distribution of a second active intensity I ̅ 2 ω n _ according to equations: I → 2 ω n = R 2 x V ^ x 2 ω n, R 2 y V ^ y 2 ω n, R 2 z V ^ z 2 ω n; - determining an active acoustic intensity I ( ω n) and a first relative uncertainty ε i ( ω n):, with i=(x, y, z), according to following equations: - computing a frequency distribution of a first reactive intensity Q 1( ω n) according to equation: Q 1 ω n = X 1 x V ^ x 2 ω n 2 + X 1 y V ^ y 2 ω n 2 + X 1 z V ^ z 2 ω n 2; - computing a frequency distribution of a second reactive intensity Q 2( ω n) according to equation: Q 2 ω n = X 2 x V ^ x 2 ω n 2 + X 2 y V ^ y 2 ω n 2 + X 2 z V ^ z 2 ω n 2; - determining a reactive acoustic intensity Q ( ω n) and a second relative uncertainty ε a ( ω n), according to following equations: