Diagnosis
That's electronic interference, usually because the monitor is picking up a signal from something else—like another wireless device or a poor power connection.
How to Fix It
1. On the monitor, press the VOX button to turn off the Voice-Activated mode. 2. Press the volume down button to lower the main volume. 3. Unplug the monitor from power and run it on battery only for a minute. If the noise stops, the issue is with your wall outlet or the power adapter. Try a different outlet away from routers or cordless phone bases.
If That Didn't Work
Go into the menu and manually change the channel. Cycle through channels 1, 2, 3, and 4. One of them will likely be much clearer.
Heads Up
This monitor is analog, so it's susceptible to interference from things like Wi-Fi routers, microwaves, or even LED lights. Keep it a few feet away from other electronics.