A person whose sensorineural hearing loss is caused by damage to the hair cells in the cochlea typically has difficulty hearing sounds at particular frequencies, or pitches. This is because each group of hair cells is sensitive only to one frequency, and when any damage occurs, some hair cells may be affected more than others. The hair cells nearest the entrance from the middle ear, which detect high-frequency sounds, seem to be more susceptible to damage related to aging and noise. This can lead to hearing loss in the high-frequency range, making it difficult to understand speech, which contains a mix of low- and high-frequency sounds.
Sudden sensorineural hearing loss. Sensorineural hearing loss that appears suddenly can have a number of causes, including a blow to the side of the head or a sudden loud sound like an explosion. This type of hearing loss can involve a wide range of frequencies, depending on the nature of the injury. Sudden sensorineural hearing loss that has no known explanation occurs only rarely, and in a large percentage of these incidents, the people recover their hearing spontaneously. (Many physicians think these cases are the result of viral infections, but this explanation has not been confirmed.)
There have been reports of sudden sensorineural hearing loss associated with diabetes, but this is extremely rare. However, there is evidence that high blood pressure may increase damage to the small blood vessels in the cochlea of people with diabetes, which could result in sudden sensorineural hearing loss. A recent study found that people with diabetes and sudden sensorineural hearing loss were more likely to have higher blood pressure, higher cholesterol, and a higher HbA1c (an indicator of blood glucose control over the previous 2–3 months) than people with diabetes but no sudden hearing loss.
If you experience sudden hearing loss, you should report it to a physician, preferably an otolaryngologist (ear, nose, and throat specialist). It’s important to get medical attention as soon as possible, because specific medicines can often recover some or most of the hearing if they are administered early.
Noise-induced hearing loss. Hearing damage from noise exposure typically occurs in a very restricted frequency range, creating a gap in the sequence of frequencies that can be heard. The gap is usually in the high-frequency range, which can affect a person’s ability to understand speech. However, noise damage can sometimes affect such a narrow frequency range that the person may not even be aware that he has hearing loss.
Protecting your ears from loud sounds can reduce the potential for hearing loss caused by noise exposure. Many comfortable forms of hearing protection are available, including earplugs, which fit into the ear canal, and earmuffs, which secure over the ears with a band. Some people are reluctant to wear hearing protection in noisy environments because they are concerned they won’t be able to hear others talking to them. This is not something to be concerned about, however, because most people talk louder in noisy situations, so it is possible to hear conversations even with ear protection.
Age-related hearing loss. As we age, hearing loss occurs gradually, beginning with the high frequencies. In general, vowels, which account for the loudness of speech, are in the low-frequency range, while consonants, which provide the clarity of speech, are in the high-frequency range. Therefore, high-frequency hearing loss may not affect how loudly sounds are heard, but it can make speech less clear and, as a result, more difficult to understand. This is especially the case when watching television or listening to the radio, where speech is often fast and where visual cues, such as lip movements and body language, are not as readily available, as well as in noisy situations.