diff --git a/src/preprocessing/spectral_Preprocessing.py b/src/preprocessing/spectral_Preprocessing.py
index 1b05560..64b7f9e 100644
--- a/src/preprocessing/spectral_Preprocessing.py
+++ b/src/preprocessing/spectral_Preprocessing.py
@@ -502,11 +502,15 @@ class PhysicalFeatureExtractor(TransformerMixin, BaseEstimator, _ArrayAsFloat64)
             a = X[:, ia]; b = X[:, ib]
             if ftype == 'ratio':
                 denom = a + b
-                denom = np.where(np.abs(denom) < 1e-12, 1e-12, denom)
-                feats.append(((a - b) / denom).reshape(-1, 1))
+                valid = np.abs(denom) >= 1e-10
+                vals = np.zeros_like(a, dtype=np.float64)
+                vals[valid] = (a[valid] - b[valid]) / denom[valid]
+                feats.append(vals.reshape(-1, 1))
             else:  # ratio_single
-                denom = np.where(np.abs(b) < 1e-12, 1e-12, b)
-                feats.append((a / denom).reshape(-1, 1))
+                valid = np.abs(b) >= 1e-10
+                vals = np.zeros_like(a, dtype=np.float64)
+                vals[valid] = a[valid] / b[valid]
+                feats.append(vals.reshape(-1, 1))
         out = np.hstack(feats)
         out = np.nan_to_num(out, nan=0.0, posinf=0.0, neginf=0.0)
         out = np.clip(out, -1e15, 1e15)