Why cats purr???

Experts still haven't nailed down the exact mechanism that creates the purr, which happens on both the inhale and exhale for a constant sound. Cats that lose their "meows" (exhale) due to injury are often still able to purr, but cats with laryngeal paralysis lose their purr. It appears that the internal laryngeal muscles, which control the opening and closing of the space between the vocal chords (glottis), creates the purr sound. Studies have shown that this laryngeal muscle movement is controlled by a unique "neural oscillator" in the cat's brain.