diff --git a/examples/time_domain.py b/examples/time_domain.py
index d790372..d9a4ab9 100644
--- a/examples/time_domain.py
+++ b/examples/time_domain.py
@@ -31,7 +31,7 @@
 a = sfs.mono.drivingfunction.source_selection_point(n0, x0, xs)
 twin = sfs.tapering.tukey(a, .3)
 p = sfs.time.soundfield.p_array(x0, d, twin * a0, t, grid)
-p = p * 100  # scale absolute amplitude
+p = p * 30  # scale absolute amplitude
 
 plt.figure(figsize=(10, 10))
 sfs.plot.level(p, grid, cmap=my_cmap)
diff --git a/sfs/plot.py b/sfs/plot.py
index 05a9af6..2f265fe 100644
--- a/sfs/plot.py
+++ b/sfs/plot.py
@@ -3,7 +3,8 @@
 import matplotlib.pyplot as plt
 from matplotlib.patches import PathPatch
 from matplotlib.path import Path
-from matplotlib.collections import PatchCollection
+from matplotlib.collections import PatchCollection, LineCollection
+from matplotlib.colors import ListedColormap
 from mpl_toolkits import axes_grid1
 from mpl_toolkits.mplot3d import Axes3D
 import numpy as np
@@ -86,6 +87,43 @@ def secondarysource_2d(x0, n0, grid=None):
         ax.add_artist(ss)
 
 
+def secondarysourcecontour_2d(x0, a0=True, ax=None):
+    """Draw contour of secondary source distribution as polygon.
+
+    Parameters
+    ----------
+    x0 : (N, 3) array_like
+        Secondary source positions.
+    a0 : bool or (N,) array_like, optional
+        Active secondary sources.
+    ax : Axes object, optional
+        The loudspeakers are plotted into this `matplotlib.axes.Axes`
+        object or -- if not specified -- into the current axes.
+    """
+    x0 = util.asarray_of_rows(x0)
+    a0 = util.asarray_1d(a0)
+
+    # colormap with black and gray to indicate active parts
+    cmap = ListedColormap(np.stack((.5*np.ones(3), np.zeros(3))))
+
+    # setup line collection with secondary source contour
+    x0 = np.append(x0, x0[0:1, :], axis=0)
+    points = np.array([x0[:, 0], x0[:, 1]]).T.reshape(-1, 1, 2)
+    segments = np.concatenate([points[:-1], points[1:]], axis=1)
+    lc = LineCollection(segments, cmap=cmap)
+    lc.set_linewidth(2)
+
+    # set color of line to indicate active parts
+    a0 = np.append(a0, a0[0])
+    active = np.logical_and(a0[0:-1], a0[1:])
+    lc.set_array(active)
+
+    # add collection of lines to current axis
+    if ax is None:
+        ax = plt.gca()
+    plt.gca().add_collection(lc)
+
+
 def loudspeaker_2d(x0, n0, a0=0.5, size=0.08, show_numbers=False, grid=None,
                    ax=None):
     """Draw loudspeaker symbols at given locations and angles.