A recent story in the UK Newspaper, The Times (www.timesonline.co.uk) reported that based on a survey conducted by ENT surgeons, earphones from portable music players may have actually prevented hearing loss in the wake of the terrorist bombings that occurred in London on July 7, 2005.
Audiology Online interviewed Brian Fligor, Sc.D. from Children's Hospital of Boston to obtain additional scientific insight on how these headphones would be able to protect users' hearing. Dr. Fligor cited unpublished data that he collected with Dr. Terri Ives from PCO School of Audiology on the passive attenuation afforded by popular headphones. They found that the earbud headphones that come with the iPod Nano and supra-aural headphones provided by Koss only provided an average of 1 and 2 dB respectively, of external sound attenuation (weighted average across frequencies). Dr. Fligor indicated that there are other earphones that are designed to provide external sound attenuation, but the article above did not indicate the type of earphones that were used. It is more likely that persons were using the stock earbuds that come with most portable music players and therefore would not provide much external sound attenuation.
An alternative possibility presented by Dr. Fligor was one of "noise conditioning" of the cochlea. The individuals could have been listening at moderately high levels sufficient to induce production of heat shock proteins within the cochlea, which are known to have a protective effect against NIHL. Animal studies have shown that experimental animals exposed to moderately intense sound constituting a near-max noise dose, followed by a significant noise-overdose, have a significantly lower degree of permanent threshold shift than control animals not exposed to the earlier moderate-intense dose.
Earphones May Have Saved Victim's Hearing
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