diff --git a/src/devices/apu.c b/src/devices/apu.c
index 00d52ec..28c4101 100644
--- a/src/devices/apu.c
+++ b/src/devices/apu.c
@@ -13,7 +13,7 @@ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 WITH REGARD TO THIS SOFTWARE.
 */
 
-#define NOTE_PERIOD 0x10000
+#define NOTE_PERIOD (SAMPLE_FREQUENCY * 0x4000 / 11025)
 #define ADSR_STEP (SAMPLE_FREQUENCY / 0xf)
 
 /* clang-format off */