Hello @jadonlyon!
That sound is the sound that AirPods make when they are separated from their owner's device. The idea is if you planted them on someone with the malicious intent to track them, the person would hear the noise every time the AirPods are moved and find them. Obviously, you're not doing that. When it makes the noise, have they been separated from your iPhone for a long time? Is Bluetooth on your iPhone left on? If either of these things have happened, that could be the cause of the noise.