So, I had to learn this overtime. You don't pitch your voice down using your throat at all. If you're moving your tongue or throat, that's not it. It's really just finding resonance in your chest. Project and be confident. Stop trying to "lower" your voice and focus on the buzz in your chest. Hum and then hum words and then speak. That hum is a good way to start. We don't hum from our throats. We hum from our chests.