diff --git a/audio_filters/butterworth_filter.py b/audio_filters/butterworth_filter.py
index 4e6ea1b18fb4..31eae6703a4f 100644
--- a/audio_filters/butterworth_filter.py
+++ b/audio_filters/butterworth_filter.py
@@ -1,6 +1,7 @@
 from math import cos, sin, sqrt, tau
 
 from audio_filters.iir_filter import IIRFilter
+# Audio filter functions for signal processing
 
 """
 Create 2nd-order IIR filters with Butterworth design.