diff --git a/src/iec_bus.h b/src/iec_bus.h
index ce42864..b549b0a 100644
--- a/src/iec_bus.h
+++ b/src/iec_bus.h
@@ -471,8 +471,10 @@ public:
 		if (OutputLED) set |= 1 << PIGPIO_OUT_LED;
 		else clear |= 1 << PIGPIO_OUT_LED;
 
+#if not defined(EXPERIMENTALZERO)
 		if (OutputSound) set |= 1 << PIGPIO_OUT_SOUND;
 		else clear |= 1 << PIGPIO_OUT_SOUND;
+#endif
 
 		write32(ARM_GPIO_GPSET0, set);
 		write32(ARM_GPIO_GPCLR0, clear);