diff --git a/notes.md b/notes.md
index 29ef053..b927c36 100644
--- a/notes.md
+++ b/notes.md
@@ -31,3 +31,11 @@
   is not a linear relationship
  - the speaker's datasheet has a graph of this which can be used to
    adjust the speaker's volume at the problematic frequencies
+
+## 2024-04-03
+- other speakers sold on DigiKey have more stable frequency response
+  graphs where the volume does not fluctuate very much compared to the
+  speaker included in the kit
+- those speakers however use sine waves instead of square waves, so our
+  first step should be focused on figuring out how to send sine waves at
+  certain frequencies, perhaps with fast PWM