Method for processing a digital audio signal for achieving spatialization of sound, said method being applied by a digital signal processor having libraries for calculating Fourier transforms from complex number space to complex number space, for digital processing of P input signals, P being an integer greater than or equal to 2, for filtering said P input signals by the convolution of sampled fast Fourier transforms, thereby obtaining Q output signals, Q being an integer equal to 2, characterized in that the method comprises at least the following steps: - grouping said P input signals by twos, one representing the real part, the other the imaginary part of a complex number, thereby defining an input vector, - achieving filtering on said input vector by passing through the Fourier space, thereby generating a complex output vector, the real portion and the imaginary portion of said output vector representing one of said Q output signals respectively and in which said output signal is obtained in the following way: - a filtering operator is applied on said input vector giving a result, - the result of the preceding step is subject to an inverse fast Fourier transform, thereby obtaining said output vector, and wherein: - P = Q = 2, - e 1 (t) and e 2 (t) are said input P input signals, - s 1 (t) and s 2 (t) are said Q output signals, - a(t), b(t), c(t) and d(t) are filters defined such that: s 1 t s 2 t = a t d t b t c t ⊗ e 1 t e 2 t wherein ⊗ is the convolution operator, - e0(t) is said input vector such that e0(t) = e 1 (t) + j.e 2 (t), - s0(t) is said output vector such that s0(t) = s 1 (t) + j.s 2 (t), - said filtering operator is such that: S = F + H 2 ⋅ E + F − H 2 ⋅ E ̃ * wherein: * is the conjugate complex operator, ∼ is the operator for inverting indices and E f = FFT e 0 t, S f = FFT s 0 t, F f = FFT a t + j. b t, H f = FFT c t − j. d t, wherein FFT designates the fast Fourier transform operator. - grouping said P input signals by twos, one representing the real part, the other the imaginary part of a complex number, thereby defining an input vector, - achieving filtering on said input vector by passing through the Fourier space, thereby generating a complex output vector, the real portion and the imaginary portion of said output vector representing one of said Q output signals respectively and in which said output signal is obtained in the following way: - a filtering operator is applied on said input vector giving a result, - the result of the preceding step is subject to an inverse fast Fourier transform, thereby obtaining said output vector, and wherein: - P = Q = 2, - e 1 (t) and e 2 (t) are said input P input signals, - s 1 (t) and s 2 (t) are said Q output signals, - a(t), b(t), c(t) and d(t) are filters defined such that: s 1 t s 2 t = a t d t b t c t ⊗ e 1 t e 2 t wherein ⊗ is the convolution operator, - e0(t) is said input vector such that e0(t) = e 1 (t) + j.e 2 (t), - s0(t) is said output vector such that s0(t) = s 1 (t) + j.s 2 (t), - said filtering operator is such that: S = F + H 2 ⋅ E + F − H 2 ⋅ E ̃ * wherein: * is the conjugate complex operator, ∼ is the operator for inverting indices and E f = FFT e 0 t, S f = FFT s 0 t, F f = FFT a t + j. b t, H f = FFT c t − j. d t, wherein FFT designates the fast Fourier transform operator. - a filtering operator is applied on said input vector giving a result, - the result of the preceding step is subject to an inverse fast Fourier transform, thereby obtaining said output vector, and wherein: - P = Q = 2, - e 1 (t) and e 2 (t) are said input P input signals, - s 1 (t) and s 2 (t) are said Q output signals, - a(t), b(t), c(t) and d(t) are filters defined such that: s 1 t s 2 t = a t d t b t c t ⊗ e 1 t e 2 t wherein ⊗ is the convolution operator, - e0(t) is said input vector such that e0(t) = e 1 (t) + j.e 2 (t), - s0(t) is said output vector such that s0(t) = s 1 (t) + j.s 2 (t), - said filtering operator is such that: S = F + H 2 ⋅ E + F − H 2 ⋅ E ̃ * wherein: * is the conjugate complex operator, ∼ is the operator for inverting indices and E f = FFT e 0 t, S f = FFT s 0 t, F f = FFT a t + j. b t, H f = FFT c t − j. d t, wherein FFT designates the fast Fourier transform operator. - P = Q = 2, - e 1 (t) and e 2 (t) are said input P input signals, - s 1 (t) and s 2 (t) are said Q output signals, - a(t), b(t), c(t) and d(t) are filters defined such that: s 1 t s 2 t = a t d t b t c t ⊗ e 1 t e 2 t wherein ⊗ is the convolution operator, - e0(t) is said input vector such that e0(t) = e 1 (t) + j.e 2 (t), - s0(t) is said output vector such that s0(t) = s 1 (t) + j.s 2 (t), - said filtering operator is such that: S = F + H 2 ⋅ E + F − H 2 ⋅ E ̃ * wherein: * is the conjugate complex operator, ∼ is the operator for inverting indices and E f = FFT e 0 t, S f = FFT s 0 t, F f = FFT a t + j. b t, H f = FFT c t − j. d t, wherein FFT designates the fast Fourier transform operator. * is the conjugate complex operator, ∼ is the operator for inverting indices