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Animals are able to make sounds by creating vibrations of vocal cords or folds. These fibrous cords are part a rigid chamber at the beginning of the trachea or windpipe called the larynx or voice box. The vocal folds open and close the opening of the trachea, producing the characteristic bark and growls of dogs, the meow and purr of cats, and our own voices. When the vocal folds close, they close the tracheal airway. This is why we can’t breathe and talk at the same time. The same is true when dogs bark and cats meow.
The cat is unique in that its vocal fold cords have an additional membrane called the ventricular cords that are used for purring. They can vibrate these rapidly without closing the trachea completely and can breathe when they are purring. So how do animals lose their voice?
Vocal sounds are made by the physical vibration of the vocal folds. The vibrations are initiated and controlled by nervous signals from the brain through nerves to the larynx. Changes or loss of voice are caused for two reasons: mechanical interference with vocal cord vibration or lack of stimulation of the nerves to the vocal cords.
Simply put, this is anything that physically makes it hard for the vocal cords to vibrate. Our cold virus is a good example. The swelling from infection and inflammation interferes with normal cord function and our voice changes. However, upper respiratory infections are not the major source of voice loss in dogs and cats.
Although some young animals may have voice changes with severe neonatal virus infections, this seldom happens in older animals. Mechanical interference is more likely to be caused by:
Decreased or non-stimulation of the nerves to the vocal cords will cause paralysis and voice changes or loss. There are many causes of neurological interference.
Unlike us, colds and flus are not the major reason for voice changes and loss in pets. If your dog or cat is losing their bark or meow do not put off a visit to your vet. Many of these conditions are treatable or easily managed.
With less treatable conditions, early intervention can lead to a longer, higher quality of life.
Dr. Ken Tudor writing for PetMD