Types of Hearing Loss




Conductive hearing loss occurs when sound cannot pass through the ear canal, ear drum or middle ear system. This category of hearing loss acts much as a plug of cotton would: sounds seem soft but speech remains clear, if it is loud enough. Some of the most often encountered conductive problems include: IMPACTED CERUMEN (ear wax plug); TYMPANIC PERFORATION (hole in the eardrum); OTITIS MEDIA (middle ear infections) which are most common in children but are also present in adults; OSSICULAR DISCONTINUITY (break or disruption in one of the three bones present in the middle ear); and OTOSCLEROSIS (bony growth) which cements the stapes (one of the three middle ear bones) at its connection point, hindering the normal passage of sounds to the inner ear.

Sensory-neural hearing loss or nerve deafness as it is commonly called, occurs when there is either a problem with the inner ear, or the nerves that transmit sound information to the brain, Individuals with this type of loss often have trouble in certain situations: a crowded room, with a softly-spoken individual, while watching the television, etc., in addition, such individuals often complain of having difficulty understanding conversation, even when sounds are presented at a loud enough level. Some of the most common factors that contribute to this type of hearing impairment are: CONGENITAL DISORDERS (those conditions present prior, at or shortly after birth, such as rubella); NOISE INDUCED HEARING LOSS, which can be due to one loud traumatic incident or extended exposure to noise over time; DRUG RELATED HEARING LOSS with certain drugs, such as quinine; MENIERS DISEASE, which typically affects only one ear, fluctuates, and is accompanied by TINNITUS (ringing) and VERTIGO (dizziness); TUMORS that grow along the auditory nerve; and finally, PRESBYCUSIS (age-related hearing loss) which affects the hair cells in the cochlea.

High Frequency Hearing Loss is one of the most common hearing disorders. It is not only caused by aging, but also by other factors such as exposure to high levels of noise and the intake of some antibiotics or other ototoxic drugs (ie. medication toxic to the ears). Noise Induced Hearing Loss is the medical term to describe a hearing loss acquired by exposure to loud noises. This could happen at work or through leisure activities such as power boats, air boats, music concerts etc. Noise polution is becoming one of the most common causes of hearing loss in our society. The long-term effect of loud noise exposure is a high frequency hearing loss.  

How The Ear Hears
The young and healthy human ear can normally hear sound frequencies (tones) varying from a very low pitch of 20 Hz up to a very high pitch of 20,000 Hz. As we grow older, we tend to lose sensitivity to the higher pitched sounds due to the degeneration of the hair cells in the cochlea- the name of the snail-shaped organ situated in the internal part of the ear. There are approximately 30,000 hair cells inside the cochlea, which respond to different frequencies. As we grow older these hair cells begin to degenerate, starting with the cells which respond to the higher frequencies.

What is it like to have a high frequency hearing loss? To have a high frequency hearing loss means that one hears all the different sounds but the high pitched ones are not heard at their correct volume. In practical terms it means that speech sounds like "s", "f", "th" and "ch" for instance, cannot be detected, making it difficult to distinguish between words such as "fix"/"six", "face"/"faith" , "deaf"/ "death", "chat"/"fat", among others. It is hardly surprising that misunderstandings result!

However, a high frequency hearing loss can easily go unnoticed and may be hard to accept, as it does not create a problem in many situations. In a one to one conversation in a quiet environment, for instance, it may not cause any problems at all.

Background noise increases the problem. When trying to follow a conversation at a social function, for example, the background noise can be very loud, yet the person speaking next to us may seem to be mumbling. If we know the topic of the conversation and do some lip-reading, we may be able to make up for what we don't hear, but if we arrive in the middle of an unfamiliar topic, we won't have much hope of understanding the conversation.

Hearing difficulties occur because background noise consists mainly of low frequency sounds which someone with a high frequency hearing loss can hear very well. In such situations good high frequency hearing is very important to allow discrimination of the different speech sounds from the background noise.

Isolation may be the consequence of a high frequency hearing loss due to withdrawal from social situations. It is certainly frustrating to go to parties and social gatherings when you cannot take part in the conversation.

As the hearing loss progresses the low tones are also affected. This is when it becomes difficult to converse even in quiet situations. The volume of the TV may need to be louder, and people may talk louder as they cannot monitor the volume of their own voices. At this stage very little communication takes place and the person may withdraw from social and family contact.

A simple hearing loss in an elderly person may be mistaken for senility, forgetfulness or just being vague, when in fact the brain is functioning normally. The aging hearing system, may in such cases, be the main reason for all the misunderstandings, confusion and apparent memory impairment!

Other related hearing disorders

Recruitment is a paradoxical phenomenon present in hearing losses due to cochlear damage. Soft sounds cannot be heard, sounds which are not uncomfortably loud to the normal ear are perceived as incredibly loud and even painful by the aging ear. It is due to recruitment that many elderly people cannot tolerate loud music or even the sound of children's voices.

Tinnitus is another phenomenon which is often experienced by those with a hearing loss. Tinnitus is the medical term used to describe those "ear or head noises" which may sound like ringing, hissing, roaring, "cicadas" etc... and which are not related to any external source. It is usually one of the symptoms of a hearing loss.

Other conditions that affect hearing:

  • Wax or foreign body in the external canal
  • Swelling of the skin tissue in the ear canal
  • Fluid in the middle ear (otitis media, common ear infection)
  • Eustachian tube swelling
  • Adenoid swelling - chronic infection
  • Menieres disease
  • Sensory-neural hearing loss and Presbycusis