 Similar to how humans learn to speak, animals learn to growl through vibration of their vocal cords that occurs when air enters the larynx and passes over them.Organisms such as Dogs tend to have a lower frequency when growling in proportion to the length of their neck, a longer neck will cause a lower frequency.Growling usually first appears in dogs when puppies are about 24 days of age during play fights, emitting a pitch of up to 450 Hz with great variation in consistency.