diff --git a/tests/test_flight_2.csv b/tests/test_flight_2.csv
index 6f4aab4..5c81eee 100644
--- a/tests/test_flight_2.csv
+++ b/tests/test_flight_2.csv
@@ -1,2 +1,2 @@
 segment, startxyz, endxyz, speeds
-constant-speed flyby, -10 20 30, 10 20 30, 30 30
\ No newline at end of file
+constant-speed flyby, 0 -10 30, 0 10 30, 30 30
\ No newline at end of file
diff --git a/tests/test_flight_3.csv b/tests/test_flight_3.csv
new file mode 100644
index 0000000..6f4aab4
--- /dev/null
+++ b/tests/test_flight_3.csv
@@ -0,0 +1,2 @@
+segment, startxyz, endxyz, speeds
+constant-speed flyby, -10 20 30, 10 20 30, 30 30
\ No newline at end of file
diff --git a/tests/tests.py b/tests/tests.py
index 71e38f9..3c891f0 100644
--- a/tests/tests.py
+++ b/tests/tests.py
@@ -107,6 +107,10 @@ def __init__(self, methodName: str = "runTest") -> None:
         renderer_2 = UASEventRenderer(params_2, 'asphalt', fs, 1.5)
         self.xout_2 = renderer_2.render(self.x)
 
+        params_3 = utils.load_params('tests/test_flight_3.csv')
+        renderer_3 = UASEventRenderer(params_3, 'asphalt', fs, 1.5)
+        self.xout_3 = renderer_3.render(self.x)
+
     def test_output_sensible(self):
         # rendering should equal length of calculated trajectory
         self.assertEqual(len(self.renderer._flightpath.T), len(self.xout))
@@ -123,4 +127,10 @@ def test_output_sensible(self):
         self.assertTrue((self.renderer.r[:n] == 0).all())
 
         # rendering of greater distance should have lower max amplitude
-        self.assertGreater(np.max(abs(self.xout)), np.max(abs(self.xout_2)))
+        self.assertGreater(np.max(abs(self.xout)), np.max(abs(self.xout_3)))
+
+        # rendering of flight along Y should result in zero signal in Y channel
+        self.assertAlmostEqual(self.xout.T[1].sum(), 0)
+
+        # rendering of flight along X should result in zero signal in X channel
+        self.assertAlmostEqual(self.xout_2.T[3].sum(), 0)
diff --git a/uasevent/environment_model.py b/uasevent/environment_model.py
index 3d1ee44..793587f 100644
--- a/uasevent/environment_model.py
+++ b/uasevent/environment_model.py
@@ -109,25 +109,27 @@ def __init__(
     ):
 
         self.max_amp = max_amp
-        self.c = c
         self.fs = fs
         self.reflection_surface = reflection_surface
-        self.theta, self.phi, self.r = utils.cart_to_sph(flightpath)
 
         # calculate delays and amplitude curve
-        delays = (self.r / self.c) * self.fs
+        _, _, r = utils.cart_to_sph(flightpath)
+        delays = (r / c) * self.fs
         self.init_delay = delays[0]
         self.delta_delays = np.diff(delays)
-        self.amp_env = 1 / (self.r**2)
+        self.amp_env = 1 / (r**2)
 
         self.frame_len = frame_len
         self.hop_len = frame_len // 2
-        self.phi_per_frame = np.lib.stride_tricks.sliding_window_view(
-                self.phi, self.frame_len)[::self.hop_len].mean(1)
-        self.theta_per_frame = np.lib.stride_tricks.sliding_window_view(
-                self.theta, self.frame_len)[::self.hop_len].mean(1)
         self.N = N
 
+        # calculate angles per frame for reflection filter and spatialisation
+        position_per_frame = np.lib.stride_tricks.sliding_window_view(
+            flightpath, self.frame_len, 1)[:, ::self.hop_len].mean(2)
+
+        self.theta_per_frame, self.phi_per_frame, _ = \
+            utils.cart_to_sph(position_per_frame)
+
     def apply_doppler(self, x):
         # init output array and initial read position
         out = np.zeros(len(self.delta_delays) + 1)
@@ -192,7 +194,7 @@ def spatialise(self, x):
         return x_out
 
     def process(self, x):
-        if len(x) < len(self.r):
+        if len(x) < len(self.delta_delays + 1):
             raise ValueError('Input signal shorter than path to be rendered')
 
         return \