Audiology/Otolaryngology/Hearing loss

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Expert: Daniel J. Bosnyak, PhD - 10/26/2009


Question
Hi,
How is hearing lost due to loud noises?

Thanks for the help
Regards
Jeff

Answer
Jeff,

That is a very good question, and one that scientists are only beginning to fully understand the answer to.  There is actually more than one way that this can happen.  Of course in the case of an explosion or something like it, the eardrum itself can be ruptured.  I assume you are not talking about that but rather medium or long term exposure to loud noises.

Inside the inner ear there are some complicated structures that are responsible for converting the sound energy into neural impulses for the brain.  A type of nerve cell known as a 'hair cell' (different from the ones on your head) senses the vibration in the sound and as a result triggers a nerve impulse.  These hair cells can be detached from the membrane they are connected to, and this detachment results in an often temporary loss of hearing.  In many cases the detachment heals and hearing returns after a day or two.  In other cases, the extreme over-activity of the hair cells actually builds up a form of metabolic poison (free radicals) inside the cell, causing eventual cell death.  This process can continue for as many as 30 days after noise exposure.  There is some recent research that shows that anti-oxidants such as vitamin A or E can help to prevent this - even if you take them after the noise exposure (within a few hours).  Of course the best way to prevent hearing loss due to loud noises is to avoid them if possible or use appropriate hearing protection otherwise.  Once the hair cells have died, your hearing ability will be permanently impaired.

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Daniel J. Bosnyak, PhD

Expertise

I am a neuroscientist and experimental psychologist who specializes in the study of Tinnitus (ringing of the ears). Our laboratory focuses on trying to understand what causes the tinnitus sensation, which we believe is an important first step in developing a cure for this debilitating illness. We believe that in many cases the sensation is generated as a result of changes in brain organization resulting from mild or moderate hearing loss, a phenomenon known as 'cortical plasticity' and akin in some ways to phantom limb pain. Although we do not offer treatment for tinnitus patients at this time, I do attend most of the worldwide conferences on Tinnitus and I am aware of most of the recent advances in treatment methodologies. Our research has been supported by the American Tinnitus Association, the Canadian Institute for Health Research and the Tinnitus Research Initiative.

Experience

As a research scientist and Adjunct Assistant Professor in the department of Psychology, Neuroscience and Behaviour at McMaster University I have been studying tinnitus and associated phenomena for several years.

Publications
Bosnyak, D. J., Gander, P. E., & Roberts, L. E. (2007). Does auditory discrimination training modify representations in both primary and secondary auditory cortex. New Frontiers in Biomagnetism. International Congress Series (pp. 25-28). Amsterdam: Elsevier Science. Roberts LE, Moffat G, Baumann, M, Ward LM, and Bosnyak DJ (2007). Residual inhibition functions overlap tinnitus spectra and the region of auditory threshold shift. Journal of Research in Otolaryngology. Roberts, L.E., Moffat, G., & Bosnyak, D. J. (2006). Residual inhibition functions in relation to tinnitus spectra and auditory threshold shift. Acta Otolaryngologica, 126, 27-33 Bosnyak D.J., Leone A.M., Gander P.E., Roberts L.E. (2007). Responses in the primary auditory cortex in tinnitus sufferers after induction of residual inhibition by masking sounds. Annual meeting of the Canadian Association for Neuroscience, Toronto, May 23-25.

Education/Credentials
MCMASTER UNIVERSITY PhD, Psychology, 2003. Hons B.A., Psychology, 1994, Summa Cum Laude

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