It can be a very frustrating situation to dislike your speaking voice. After all, you have to hear it in practically everything you do every day, whether you're socialising with your friends, giving your puppy "commands" or making important phone calls at work. If you find that your voice is perhaps too squeaky, high or thin, and want a voice that perhaps has a more commanding sound, there are several things that you can do to naturally deepen it.
Try voice training exercises. Stand straight in front of a mirror. Pick up a book and read it aloud for about 15 minutes. Slow down your talking speed and instead focus on the your pronunciation and enunciation. The faster you talk, the more tension it puts on your voice box, leading to a higher voice. Keep your talking speed slow and relaxed. Try a word repetition exercise as well. Keep repeating gibberish such as "dong dong" and "boom boom" over and over, while trying to slowly lower your voice every time.
Practice proper posture. Whenever you are talking, concentrate on keeping your chin up. Also keep your head looking straight ahead at all times.
Do not yell. No matter how stressed out you may be, abstain from yelling. This puts a lot of stress on your vocal cords, and can also cause you to lose control of your voice. If you want to speak in a calm and deep tone, avoid yelling.
Quit smoking cigarettes. If you're a smoker, it is a habit you need to stop immediately if you want to attain a deeper voice. Cigarettes can wreak destruction upon the lungs and throat, making a person feel much more pressure when talking (due to muscle tightening).
Sleep a lot. Sufficient sleep can bring a wide array of benefits, and a deeper voice is one of them. If you are sleep-deprived, it can cause your voice to become hoarse, crackly, weak, fragile and thin. Try to receive a minimum of 7 hours of shut-eye nightly to achieve a smooth, deep and controlled vocal tone.
Stay hydrated. Drink a lot of water to maintain a damp throat. The wetter your throat is, the more control over your voice you will have.