diff --git a/tool/test_frequency_and_SNR.py b/tool/test_frequency_and_SNR.py
index 41e7425..ad8f095 100755
--- a/tool/test_frequency_and_SNR.py
+++ b/tool/test_frequency_and_SNR.py
@@ -15,7 +15,7 @@
     for freq in magic_rates:
         audio_name, audio_ext = os.path.splitext(audio_file)
         audio_freq = audio_name + "-" + str(freq) + audio_ext
-        os.system("sox " + audio_file + " -G -r " + str(freq) + " -b 8 -c 1 " + audio_freq)
+        os.system("sox -G -v 0.92 " + audio_file + " -r " + str(freq) + " -b 8 -c 1 " + audio_freq)
         if audio_ext in ('.wav', '.WAV'):
             audio_module = wave
         else: