Added calculation of critical distance

pyrato/parametric.py

@@ -187,6 +187,42 @@ def air_attenuation_coefficient(
 
     return air_abs_coeff
 
+
+def critical_distance(
+                     volume,
+                     reverberation_time):
+    r"""Calculate the critical distance of a room with
+    given volume and reverberation time.
+    Assumes the source directivity is 1 (omnidirectional source).
+    See [#kra]_.
+
+    .. math::
+        d_c = 0.057 \sqrt{\frac{V}{T_{60}}}
+
+    Parameters
+    ----------
+    volume : double
+        Volume of the room in cubic meters.
+    reverberation_time : double
+        Reverberation time of the room in seconds.
+
+    Returns
+    -------
+    critical_dist : double
+        The resulting critical distance in meters.
+
+    References
+    ----------
+    .. [#kra] H. Kuttruff, Room acoustics, 4th Ed. Taylor & Francis, 2009.
+
+    """
+    if reverberation_time <= 0:
+        raise ValueError("Reverberation time must be greater than zero.")
+    if volume <= 0:
+        raise ValueError("Volume must be greater than zero.")
+    critical_dist = 0.057 * np.sqrt(volume / reverberation_time)
+    return critical_dist
+
 
 def mean_free_path(
         volume,

tests/test_parametric.py

@@ -1,8 +1,28 @@
 """Tests for parametric related things."""
 
+import numpy.testing as npt
+import pytest
+import pyrato.parametric as parametric
 from pyrato.parametric import mean_free_path
 import pyrato as ra
-import pytest
+
+
+@pytest.mark.parametrize(("volume","reverberation_time","expected_critical_distance"),
+        [(100, 1, 0.57),(200, 2, 0.57),(50, 0.5, 0.57),(150, 3, 0.403050865)])
+def test_critical_distance_calculate(volume, reverberation_time,
+                                     expected_critical_distance):
+    critical_distance = parametric.critical_distance(
+        volume, reverberation_time)
+    npt.assert_allclose(critical_distance,
+                        expected_critical_distance,
+                        atol=1e-2)
+
+
+@pytest.mark.parametrize(("volume","reverberation_time"),
+        [(100, 0),(0, 2),(0, 0),(-20, 3),(20, -1)])
+def test_critical_distance_error(volume, reverberation_time):
+    with pytest.raises(ValueError, match='must be greater than zero.'):
+        parametric.critical_distance(volume, reverberation_time)
 
 
 @pytest.mark.parametrize(