The sense of hearing in the average cat is much more fine-tuned than that of a human, allowing it to detect much higher sound pitches. The upper range of hearing is thought to be around 60,000 kilohertz for cats, well above the 20,000-kilohertz norm for people.
Anatomy and Physiology
The feline hearing apparatus can be divided into three portions: the inner ear, the middle ear, and the external ear canal and associated structures. The inner ear is that portion containing the nerve endings responsible for the sensation of hearing.
It also plays a leading role in maintaining balance and equilibrium in your pet (cats get carsick, too!). The inner ear apparatus lies protected within the bony confines of the skull. The nerves and associated structures within the inner ear are very sensitive and can be damaged through continued exposure to loud, high-pitched noises, infections, and/or toxic medications.
The middle ear communicates directly with the inner ear and is contained within a pear-shaped bony cavity originating from the skull called the tympanic bulla. This middle-ear cavity is normally filled with air and contains blood vessels and nerves that supply the face and the rest of the head.
Inflammation involving the middle ear can adversely affect these nerves, leading to paralysis of the muscles of the face. The eardrum, or tympanic membrane, separates the middle ear from the external ear canal.
This external canal directly communicates to the outside world, but not without first going through some significant anatomical changes along the way. A horizontal portion of the canal courses a short distance directly away from the eardrum before angling sharply upward to form a long vertical portion.
This distinct bend has medical significance in that it can lead to the entrapment of wax, hair, and debris deep within the ear, predisposing to inflammation and infection. These substances can be removed by application of a liquid cleansing agent.
The vertical external ear canal—and to a lesser extent, the horizontal ear canal—are lined with special glands that produce ear wax, or cerumen. In the past, cerumen was thought to exert some beneficial antibacterial effects in the ear.
Yet research has disproved this and has shown that too much of a waxy buildup can actually promote bacterial growth and infections. In the healthy ear with normal amounts of cerumen produced, this doesn’t present much of a problem.
Yet when an ear becomes inflamed, wax production increases, and can predispose to infectious complications. Surrounding the opening of the external ear canals is the earflap, or pinna. Each pinna is supported by a sturdy band of cartilage that courses from the vertical ear canal to the tip of each flap.