The document summarizes the four stages of voice production:
1. Compression - The air is compressed in the lungs before exhalation through the process of breathing.
2. Vibration - When the exhaled air hits the vocal folds in the larynx, it causes them to vibrate, producing an initial sound.
3. Amplification - The vestibule, pharynx, nasal cavities, and mouth act as resonators, amplifying the vibrations into the actual voice.
4. Modification - The lips, teeth, tongue, and jaw articulate and shape the amplified sound into distinguishable vowels and consonants through speech.