diff --git a/FlashSR/Util/UtilAudioLowPassFilter.py b/FlashSR/Util/UtilAudioLowPassFilter.py
index 31a5ae1..657e904 100755
--- a/FlashSR/Util/UtilAudioLowPassFilter.py
+++ b/FlashSR/Util/UtilAudioLowPassFilter.py
@@ -37,14 +37,18 @@ def lowpass(audio:ndarray, #[time] 1d array
     
     @staticmethod
     def lowpass_filter(x:ndarray, #[time] 1d array
-                       highcutoff_freq:float, #high cutoff frequency
-                       fs:int, 
-                       order:int, #the order of filter
-                       ftype:Literal['butter', 'cheby1', 'cheby2', 'ellip', 'bessel'],
-                       upsample_to_original:bool = True
-                       ) -> ndarray: #[time] 1d array
+                   highcutoff_freq:float, #high cutoff frequency
+                   fs:int, 
+                   order:int, #the order of filter
+                   ftype:Literal['butter', 'cheby1', 'cheby2', 'ellip', 'bessel'],
+                   upsample_to_original:bool = True
+                   ) -> ndarray: #[time] 1d array
         nyq = 0.5 * fs
+        # Ensure hi is between 0 and 1 (exclusive)
         hi = highcutoff_freq / nyq
+        hi = min(hi, 0.999)  # Clamp to just below 1
+        hi = max(hi, 0.001)  # Clamp to just above 0
+    
         if ftype == "butter":
             sos = butter(order, hi, btype="low", output="sos")
         elif ftype == "cheby1":
@@ -106,4 +110,4 @@ def subsampling(data, lowpass_ratio, fs_ori=44100, upsample_to_original:bool = T
     
 if __name__ == "__main__":
     util = UtilAudioLowPassFilter()
-    util.lowpass(np.zeros(24000),48000, filter_name="cheby", filter_order=8, cutoff_freq=8000)
\ No newline at end of file
+    util.lowpass(np.zeros(24000),48000, filter_name="cheby", filter_order=8, cutoff_freq=8000)