Hearing loss can be categorized by which part of the auditory system is damaged. There are three basic types of hearing loss: conductive hearing loss, sensorineural hearing loss, and mixed hearing loss.
Mixed Hearing Loss
When people suffer from mixed hearing loss, they have a combination of two separate hearing health issues. The two types of hearing problems that co-exist to produce mixed hearing loss are conductive and sensorineural hearing loss.With this sort of hearing loss, the inner ear and middle ear may be affected.
Conductive Hearing Loss
This occurs when sound is incapable of reaching the cochlea. This is merely due to malformation of the ear canal or the outer ear—it is not due to problems associated with the delicate cochlea. Thus, it is often capable of being fixed through simple surgical procedures. However, there can often arise problems with the ossicles (the bones of the middle ear), which can lead to conductive hearing loss. This can be due to trauma if something is shoved inside of the ear, since the ossicles are the first line in the chain of transmission (after the eardrum) of transmitting acoustic information to the cochlea.
Sensorineural Hearing Loss
Sensorineural hearing loss involves dysfunction of the middle ear. Here, the cochlea, hair cells, or nerve cells do not properly wire or function, causing the actual neural circuitry of the ear to malfunction. This leads to hearing loss. One of the most typical causes of hearing, loss of this type is damage to the all-important hair cells of the cochlea. These cells are responsible for ultimately converting the vibrations of acoustic signals to electro-chemical signals of the nervous system. Without these cells, the nervous system is not able to “hear” any of the vibrations. The fact that these cells do not regrow means that any damage to them is permanent. Indeed, 50% or more of people above 70 have some form of hearing loss for precisely this reason : throughout their life, they have depleted many of the finite number of hair cells in the inner ear, causing long-term and permanent hearing loss.
Some conditions involve mixed loss of hearing, in which both sensorineural and conductive hearing loss is combined. In the case of multiple ear infections, it is often the case that the entire middle ear and inner ear would be affected. In this case, mixed hearing loss results in comprehensive problems in hearing and ear physiology.
Many adults experience a precipitous decline in their capacity to hear quiet sounds and subtle communication. This condition is also called presbycusis, and generally occurs gradually and progressively over time; rarely does it occur that an aging person loses his or her hearing in one cataclysmic event. For those with age-related hearing loss, hearing aids are often a good solution. Hearing aids, most of which are digital nowadays, are completely programmable, adjustable, and convenient. Indeed, many of them are allowed the listener to focus on a single speaker, and other models have special settings for the telephone, the television, and other electronic devices. Finally, automatic settings enable the hearing aid to automatically detect when the wearer is in a musical versus a conversational environment.
Measuring the Extent of Hearing Loss
Hearing loss can come in many different levels of intensity. The severity of hearing impairment runs on a scale from mild to total deafness.
1. Mild to Moderate Hearing Loss
Mild hearing loss means that one can hear above somewhere between 20 and 40 decibels (dB). For reference, a soft whisper at one meter is about 20 to 30 dB. This means that a mildly deaf individual listening to a person whispering from one meter away will likely barely be able to hear them. Moderate hearing problems occur when an individual cannot hear below 41 to 55 dB. This is around to the intensity level of a quiet auditorium.
2. Severe Hearing Loss
Hearing problems become very problematic when they reach a level of moderately severe which is around 56 and 70 dB. At this level of deafness, one would be unable to hear a normal conversation without great effort. Severe hearing loss occurs at around 71 and 90 dB, and this removes the capacity to soft music and louder conversation. Profound deafness, which allows one to hear only above 91 dB, means that the individual would only be barely able to hear an orchestra playing its loudest possible (fff) from the first row. Above this, those who are totally deaf have no hearing at all.
Of course, this severity of hearing impairment is far from uniform across all frequency levels. Rather, certain frequencies decline overage. It is common for the normal adult not to be able to sense supersonic frequencies that smaller children and teenagers can readily perceive.