There are no known cases of congenital mutism, present since birth, in dogs and cats. However, the complete impossibility of emitting sounds can derive from traumas to the vocal cords, even if they are rather rare phenomena. Cases of congenital or acquired deafness are more frequent. And it is possible that in this case there is a phenomenon of partial silence, because the animal cannot hear the verses it emits and therefore cannot control the sound of the voice: the most frequent consequence is the low volume of the verses emitted. A deaf animal from birth has also lacked the learning phase, so the variety of sounds emitted is generally also limited. The white ones are particularly susceptible to congenital deafness among cats. Among the dogs, the Dalmatians, the bull terriers and the scottish. Acquired deafness can result from ear infections, traumatic brain injury or old age. In any case, the animal affected by deafness or mutism develops the other senses and mimic capacity more, managing to lead a practically normal existence.