My son gets lulled to sleep with the sound of my voice. My wife and I initially thought that he was falling asleep with the sound of us conversing. But we noticed that if it was my wife who was doing most of the talking, it would take a long time for him to fall asleep.

After a little more experimentation we finally confirmed that it was indeed the sound of my voice that was putting him to sleep.

I hope it was because of the soothing sound of my baritone voice and not really because I was boring him to sleep. *snicker*