aspcol.sphericalharmonics.directivity_linear

aspcol.sphericalharmonics.directivity_linear(A, d_mic, max_order=1)

Harmonic coefficients of a linear directivity function

The directivity function is defined as c(d, omega) = A + A * d^T d_mic

Omni directivity is obtained by setting A = 0 Cardoid directivity is obtained by setting A = 1/2 Figure-8 directivity is obtained by setting A = 1

Parameters:

  • A (float) – directivity parameter. Must be between 0 and 1.

  • d_mic (ndarray of shape (num_mic, 3)) – direction of the microphone(s). It is the angle at which a cardioid microphone would give the strongest response It is the outward direction, so from the center of the microphone towards the sources Must be a unit vector

  • max_order (int) – maximum order of the spherical harmonics. If set higher than 1, the coefficients of the higher orders will be zero.

Returns:

dir_coeffs – coefficients of the directivity function

Return type:

ndarray of shape (num_mic, num_coeffs)

References

[uenoSound2018] N. Ueno, S. Koyama, and H. Saruwatari, “Sound field recording using distributed microphones based on harmonic analysis of infinite order,” IEEE Signal Process. Lett., vol. 25, no. 1, pp. 135–139, Jan. 2018, doi: 10.1109/LSP.2017.2775242. [brunnstromBayesianSubmitted] J. Brunnström, M. B. Møller, and M. Moonen, “Bayesian sound field estimation using moving microphones,” IEEE Open Journal of Signal Processing, submitted.

Notes

The directivity coefficients are defined in more detail in the supplementary notes of [uenoSound2018] and in [brunnstromBayesianSubmitted]