Update PitchShift() detection to 40Hz

Author: Spijkervet

tests/test_augmentations.py

@@ -196,9 +196,10 @@ def test_pitch_shift_transform_with_pitch_detection():
     f0_hz = f0_hz[~np.isnan(f0_hz)]
 
     detected_f0_hz = np.max(f0_hz)
-
-    # the detected frequency vs. expected frequency should not be smaller than 20Hz.
-    assert abs(detected_f0_hz - expected_frequency_shift) < 20
+    
+    detection_threshold_in_hz = 40
+    # the detected frequency vs. expected frequency should not be smaller than 40Hz.
+    assert abs(detected_f0_hz - expected_frequency_shift) < detection_threshold_in_hz
 
 
 @pytest.mark.parametrize("num_channels", [1, 2])