Purring is one of the most well-known animal sounds. It is a distinctive vocal feature shared by domestic cats, bobcats, cheetahs, lynx, and pumas. Purring behaviour is absent in larger breeds of cats, such as lions and tigers. The sound comes from the internal laryngeal muscles in the throat, which help control the glottis opening and closing (the space between the vocal folds in the larynx). When the muscles in this area oscillate, the vocal cords separate, producing a distinct sound as air moves across the surface.