xref handling

as proposed by mgeier

Author: fs446

doc/examples/wfs-referencing.ipynb

@@ -197,10 +197,10 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "xref = [0, 0.1175, 0]  # intentionally no stationary phase point\n",
+    "xref = 0, 0.1175, 0  # intentionally no stationary phase point\n",
     "#  we don't forget to normalize the point source's amplitude\n",
     "# to this new reference point:\n",
-    "normalize_gain = 4 * np.pi * np.linalg.norm(xs - np.array(xref))\n",
+    "normalize_gain = 4 * np.pi * np.linalg.norm(xs - xref)\n",
     "d, selection, secondary_source = sfs.fd.wfs.point_25d(\n",
     "    omega, array.x, array.n, xs, xref=xref)\n",
     "p_point = sound_field(\n",