Have you ever heard a recording of your voice and had a double take? You might have thought, "Is that really what my voice sounds like?" Maybe your accent is more pronounced in the recording than you realized, or your voice is higher than it seems to your own ears. This is of courese quite a common experience.
The explanation is actualy fairly simple. There are two pathways through which we perceive our own voice when we speak. One is the route through which we perceive most external sounds, like waves that travel from the air through the outer, middle and inner ear.
But because our vocal cords vibrate when we speak, there is a second internal path. Vibrations are conducted through our bones and stimulate our inner ears directly. Lower frequencies are emphasized along this pathway. That makes your voice sound deeper and richer to yourself than it may sound to other people.
That explanation makes sense for many people, but it doesn't quite explain some variations in this phenomenon, like people whose voices sound higher to themselves than it does to others. These variations occur simply because very person's hearing is different.
There are more nuanced ways for sounds to be perceived by the inner ear, which creates different perceptions between ourselves and others. For example, vibrations of your voice may encounter cerebrospinal fluid, the clear liquid that sits within the brain and spine, which can influence how you perceive your voice.
All these variations and more make it so that your voice will always sound different to your own ears than it sounds to others.