diff --git a/mysignal/phasefreq.py b/mysignal/phasefreq.py
index 5132712..f07c4d4 100644
--- a/mysignal/phasefreq.py
+++ b/mysignal/phasefreq.py
@@ -91,7 +91,7 @@ def filter_signal_by_modes(time, signal, num_modes=1, bandwidth_factor=0.1, nyqu
     return filtered_signals, dominant_freqs, time_filtered
 
 
-def analyze_signal_Hilbert(time, e_signal, s_signal):
+def analyze_signal_Hilbert(time, e_signal, s_signal, freq_rtol=0.01):
     """
     Analyzes the dominant frequencies, phase shift, time shift, and periods between two signals e_signal(t) and s_signal(t) from a DataFrame.
     Uses Hilbert transform method for phase shift calculation (single mode only).
@@ -143,8 +143,8 @@ def analyze_signal_Hilbert(time, e_signal, s_signal):
     freq_s = s_peak_freqs[s_idx]
 
     # Check if frequencies match within 1%
-    if np.abs(freq_e - freq_s) / ((freq_e + freq_s)/2) > 0.01:
-        raise ValueError("Frequency difference exceeds 1%. Phase shift cannot be determined.")
+    if np.abs(freq_e - freq_s) / ((freq_e + freq_s)/2) > freq_rtol:
+        raise ValueError(f"Frequency difference exceeds {freq_rtol*100}%. Phase shift cannot be determined.")
 
     # Calculate mean frequency for phase shift calculation
     mean_freq = (freq_e + freq_s) / 2
@@ -200,7 +200,7 @@ def analyze_signal_Hilbert(time, e_signal, s_signal):
     return (period_e, period_s, freq_e, freq_s,
             mean_phase_diff, phase_diff_deg, time_shift)
 
-def analyze_signal_sinfit(time, e_signal, s_signal):
+def analyze_signal_sinfit(time, e_signal, s_signal, freq_rtol=0.01):
     """
     Analyzes the dominant frequencies, phase shift, time shift, and periods between two signals e_signal(t) and s_signal(t) from a DataFrame.
     Uses curve fitting method for phase shift calculation (single mode only).
@@ -252,8 +252,8 @@ def analyze_signal_sinfit(time, e_signal, s_signal):
     freq_s = s_peak_freqs[s_idx]
 
     # Check if frequencies match within 1%
-    if np.abs(freq_e - freq_s) / ((freq_e + freq_s)/2) > 0.01:
-        raise ValueError("Frequency difference exceeds 1%. Phase shift cannot be determined.")
+    if np.abs(freq_e - freq_s) / ((freq_e + freq_s)/2) > freq_rtol:
+        raise ValueError(f"Frequency difference exceeds {freq_rtol*100}%. Phase shift cannot be determined.")
 
     # Calculate mean frequency for phase shift calculation
     mean_freq = (freq_e + freq_s) / 2
@@ -300,7 +300,7 @@ def analyze_signal_sinfit(time, e_signal, s_signal):
 
 
 
-def analyze_signal_cross_correlation(time, e_signal, s_signal):
+def analyze_signal_cross_correlation(time, e_signal, s_signal, freq_rtol=0.01):
     """
     Analyzes signals using cross-correlation method for phase shift calculation (single mode only).
     """
@@ -351,8 +351,8 @@ def analyze_signal_cross_correlation(time, e_signal, s_signal):
     freq_s = s_peak_freqs[s_idx]
 
     # Check if frequencies match within 1%
-    if np.abs(freq_e - freq_s) / ((freq_e + freq_s)/2) > 0.01:
-        raise ValueError("Frequency difference exceeds 1%. Phase shift cannot be determined.")
+    if np.abs(freq_e - freq_s) / ((freq_e + freq_s)/2) > freq_rtol:
+        raise ValueError(f"Frequency difference exceeds {freq_rtol*100}%. Phase shift cannot be determined.")
 
     # Calculate mean frequency for phase shift calculation
     mean_freq = (freq_e + freq_s) / 2
@@ -401,7 +401,7 @@ def analyze_signal_cross_correlation(time, e_signal, s_signal):
             phase_diff, phase_diff_deg, time_shift)
 
 
-def analyze_signal_wavelet(time, e_signal, s_signal):
+def analyze_signal_wavelet(time, e_signal, s_signal, freq_rtol=0.01):
     """
     Analyzes signals using wavelet transform for phase shift calculation (single mode only).
     """
@@ -452,8 +452,8 @@ def analyze_signal_wavelet(time, e_signal, s_signal):
     freq_s = s_peak_freqs[s_idx]
 
     # Check if frequencies match within 1%
-    if np.abs(freq_e - freq_s) / ((freq_e + freq_s)/2) > 0.01:
-        raise ValueError("Frequency difference exceeds 1%. Phase shift cannot be determined.")
+    if np.abs(freq_e - freq_s) / ((freq_e + freq_s)/2) > freq_rtol:
+        raise ValueError(f"Frequency difference exceeds {freq_rtol*100}%. Phase shift cannot be determined.")
 
     # Calculate mean frequency for phase shift calculation
     mean_freq = (freq_e + freq_s) / 2