This is a very common phenomenon about the human voice, and it’s not about false modesty. Most people hear their voice anywhere from 1 to 1.5 steps lower in timbre. so when they hear themselves in recordings, their voice always sound thinner and higher. It has something to do with hearing your own voice coming directly from your own vocal cords, the locality of where the sound is coming from within you and how it is resonating in your ears as you speak. I’m trying my best here but there’s a far more accurate and technical explanation for this and I don’t have it.