What happens when the cochlea is damaged?

Cochlea Damage The majority of hearing losses in the world are due to damage caused to the cochlea,(sensori-neural). In nearly all cases the patient will struggle with speech discrimination ( "I can hear your voice but you sound like you are muttering")


This is made even worse in the presence of background noise. The fitting of hearing aids will be beneficial, but simply amplifying sounds will not overcome the problems found in the cochlea. We will now look at the various problems within the cochlea.


Loudness Recruitment


People with cochlea damage need a greater level of sound to hear well, but when sounds get louder they become just as intolerant of loud sounds as people with no hearing impairment. As seen in audiometry, this leaves the patient with a reduced dynamic range. This causes problems with speech discrimination, as the dynamic range of speech is about 50dB i.e. a 50dB intensity difference between the loudest and quietest parts of speech.Someone with a reduced dynamic range may not be able to accommodate the whole range of speech, which could become a problem when a hearing aid is fitted.


A hearing instrument with the ability to adjust the amounts of amplification will provide a better option for patients with a reduced dynamic range.Recruitment is found only in patients with cochlea (hair cell) damage. The term "abnormal growth of loudness" is commonly used and relates to patients perception of loudness throughout their dynamic range.

A full explanation of cochlea damage can be found here.

Gunshot blasts pose a serious hazard to hearing

The impulse noise from firearms is as intense as 132-165 Db and thus extremely dangerous to
hearing.
A Polish study including 18 hunters and 8 police trainees, with average ages of 46.2 years and
25.2 years, respectively, found that as many as 72.2 percent of hunters suffered from hearing
loss. Only 11.1% had completely normal hearing, and the remaining 16.7% had normal hearing
only in the ear furthest away from the rifle.
The hunters had never used hearing protection while hunting. The police trainees had always
used hearing protection when practising target shooting and none of them suffered from
measurable hearing loss.
In a comparison of the two groups their hearing was examined before and after a number of
test gunshots. Changes were noted in the hearing of the hunters, whereas no measurable
changes were found in the police trainees after the test shots. The latter group wore hearing
protection throughout the test shooting.
The study indicated that long-term exposure to gunshot blasts is not the only hazard when
using firearms. Even short-term exposure can cause temporary hearing damage and make the
ear more susceptible to noise damage later on.
On the plus side, the study confirmed that hearing protection prevents hearing loss. The use of
hearing protection is therefore highly recommended when using firearms.
Source; International Journal of Occupational Medicine and Environmental Health
http://www.all-about-the-human-ear.com/hearingprotection.html

What is deafness from noise?

Deafness or hearing impairment resulting from prolonged exposure to loud noise is most frequently associated with industrial workplaces, airports etc. The damaging effects of this kind of noise are also the most studied type of noise-induced hearing loss.


But according to an article in "The Hearing Review", February 1999, by otolaryngolist Ken Einhorn, up to 52 % of classical musicians and up to 30 % of rock or pop musicians suffer from music-induced hearing loss, MIHL. It is hardly surprising that music can cause damage while on the job. The sound pressure of a large concert orchestra may reach 112 dB - of amplified rock bands even up to 130 dB, far more than that accepted in an industrial environment.

For the musicians who are regularly subjected to this kind of noise, the resulting problems can be devastating described as noise induced hearing loss. Symptoms begin with losing the ability to hear high-frequency sounds and tones.

In many cases, this causes problems for musicians and singers who must be able to hear and play high notes equally as well as low ones in order to play or sing along with other orchestra members. Often, a musician who suffers from loss of high frequency hearing will try to compensate by playing louder at high-pitched notes, which leads to an artistically unacceptable performance.

As the problem grows, the musician might react oversensitively: suffer from increased blood pressure, headaches, fatigue or experience some sounds or instruments as being painfully loud, a state that often leads to tinnitus.

Another common symptom is the inability to perceive changes in pitch. This state, known as displacusis, is extremely problematic for singers, who have to be in control of their voice and stay in tune at all times. A hearing-impaired singer is also at risk of damaging his or her own her voice by constantly singing louder in order to monitor his/her own voice.

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