BACKGROUND OF THE STUDY
Hearing loss is defined as diminished sensitivity to the sounds normally heard. Globally, hearing loss affects about 10% of the population to some degree. It caused moderate to severe disability in 124.2 million people as of 2004 (107.9 million of whom are in low and middle income countries). Of these, 65 million acquired the condition during childhood. At birth, around 3 per 1000 in developed countries and more than 6 per 1000 in developing countries have hearing problem.
There is a progressive loss of ability to hear high frequencies with increasing age known as presbycusis. This begins in early adulthood, but does not usually interfere with ability to understand conversation until much later. Although genetically variable it is a normal concomitant of aging and is distinct from hearing losses caused by noise exposure, toxins or disease agents.
A sensorineural hearing loss is one resulting from dysfunction of the inner ear, the cochlea, the nerve that transmits the impulses from the cochlea to the hearing center in the brain or damage in the brain. The most common reason for sensorineural hearing impairment is damage to the hair cells in the cochlea. As one grows older, the hair cells degenerate and lose their function, and our hearing deteriorates. Depending on the definition it could be estimated that more than 50% of the population over the age of 70 has an impaired hearing. Impaired hearing is the most common physical handicap in the industrialized world.
Noise-induced hearing loss
Noise-induced hearing loss (NIHL) occurs when too much sound intensity is transmitted into and through the auditory system. An acoustic signal from an energy source, such as a radio, enters into the external auditory canal, and is funneled through to the tympanic membrane (eardrum). The tympanic membrane acts as an elastic diaphragm and drives the ossicular chain of the middle ear system into motion. Then the middle ear ossicles transfer mechanical energy to the cochlea by way of the stapes footplate hammering against the oval window of the cochlea. This hammering causes the fluid within the cochlea (perilymph and endolymph) to push against the stereocilia of the hair cells, which then transmit a signal to the central auditory system within the brain. When the ear is exposed to excessive sound levels or loud sounds over time, the overstimulation of the hair cells leads to heavy production of reactive oxygen species, leading to oxidative cell death. In animal experiments, antioxidant vitamins have been found to reduce hearing loss even when administered the day after noise exposure
Singh, Bhardwaj, & Kumar (2012) concluded that levels of noise exposure and occupations wherein there is a significant, prolonged exposure to noise is significantly associated with hearing loss. Effect of Music on Hearing Loss
Musical training has been known to improve the neural representation of key acoustic features important for speech perception (Kraus and Chandrasekaran. 2010). According to a research study by Parbery-Clark, et. al. (2012), music has a significant effect on the neural mechanisms that are involved with the encoding of a sound stimulus. Musical experience was also said to reduce the effects of aging on the neural encoding of the time-course of the changes in vowel formant frequencies. Formants are the acoustic resonance of the human vocal tract, which is part of the components of human speech.
Musicians are also found to have greater proficiency on auditory-based cognitive measures, enhanced perception of speech in a noisy environment, better auditory working memory and auditory temporal acuity compared to non-musicians (Strait, D., et.al., 2011). These may be attributed by the increased neural sensitivity of musicians to acoustic irregularities. These studies show that music has a positive effect on auditory perception and cognitive processes.
Bibliography: Mirhaj, P., Khani, G., Sedaie, M., and Faghihzadeh, S.The effect of music on hearing of string musicians.Audiology. 14,2. p.56.
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