1. Tongue Height: How high or low the tongue is in the mouth. This creates the distinction between high vowels like "i" in "see" and low vowels like "a" in "father".
2. Tongue Advancement: How far forward or back in the mouth the tongue is. This creates the distinction between front vowels like "e" in "bed" and back vowels like "u" in "flute".
3. Lip Rounding: Whether the lips are rounded or spread. This creates the distinction between rounded vowels like "u" in "flute" and unrounded vowels like "i" in "see".
4. Tenseness: Whether the vowel is produced with more or less muscular tension. This creates the distinction between tense vowels like "i" in "see" and lax vowels like "ɪ" in "sit".
These four parameters work together to create the wide range of vowel sounds in any language.