Fig. 3
From: Comparative evaluation of interpolation methods for the directivity of musical instruments
The high-resolution reference of the bassoon directivety for the second overtone at f2=468 Hz is shown with the 32 sampling points in the upper left. The triangular interpolation (TrI) and spline interpolation estimate for M={1,2} is shown at the top and the results of the spherical harmonics Interpolation (SH) for N={4,5,...,8} at the bottom. The difference of sound pressure level in dB between reference and interpolation is shown over azimuth and colatitude, the gray crosses indicate the sampling points. The result for the spline interpolation with M=3 is not included in this figure, but is shown in detail in Fig. 6