Page 18 - Fall 2007

MODERN MUSIC-PLAYING DEVICES AS HEARING HEALTH RISKS
Brenda L. Lonsbury-Martin
and
Glen K. Martin
Research Service, Veterans Affairs Loma Linda Healthcare System Loma Linda, California 92357
Noise-induced hearing loss
(NIHL) is a disorder that is
common throughout the indus-
trialized world. Exposure to excessive
sounds produces a complex set of
harmful effects that happen painlessly
and silently to the delicate inner-ear
structures responsible for the initial
stages of hearing. NIHL has always
been associated with noisy work-places
(e.g., factory machinery, construction
tools, farming equipment). In more
recent times, other threats to healthy
hearing have included loud leisure-
time activities involving, for example,
sporting events, live amplified music, and recreational shoot- ing. However, it is only within the past few decades that the general availability of personal music-players has made the risk of hearing damage seem more menacing.
Recently, several studies have reported an increasing trend of NIHL in children and adolescents. For example, Chung et al. (2005) posted a web-based survey on the Music Television Video (MTV) web site to obtain general health information from the MTV generation including whether these individuals were aware that over-exposure to loud music could result in a hearing loss. The results from almost 10,000 completed surveys were somewhat disheartening in that hearing loss was ranked as a low priority relative to other health issues such as sexually transmitted diseases, alco- hol/drug use, depression, smoking, nutrition and weight issues, and acne. Surprisingly, most respondents had experi- enced tinnitus (i.e., ringing in the ears or head) and hearing impairment after attending concerts and clubs. However, one hopeful finding of the study was that many adolescents and young adults indicated that they would wear hearing protection to avoid a lifelong hearing loss condition, if they were advised to do so by a medical professional.
Most certainly, the media have contributed to the fear that the recent rise in popularity of digital audio entertain- ment devices like MP3 players and personal music players is causing more frequent hearing loss than ever before and at younger ages than earlier models of portable music-playing devices such as transistor radios and personal cassette stereo players. Clearly, modern audio technology with its long-last- ing lithium-ion batteries, internal gigabyte memory-storage capability, and snugly fitting insert earphones (e.g., earbuds) presents a genuine hearing hazard, the degree of which is
“Most certainly, the media have contributed to the fear that the recent rise in popularity of MP3 players and personal music players is causing more frequent hearing loss than ever before and at younger ages”
related to both the level of noise as well as to the duration of the exposure.
Whether the expectation of a rise in hearing problems in children and adolescents due to portable media players is real or not is undergoing active debate at this time. While many parents, in particular, are concerned about the potential risk of hearing loss from the over-use of personal music- playing devices, cynics maintain that there are serious problems that include sampling errors in recent surveys like the one mentioned above and in opin- ion polls claiming digital audio players
are causing greater hearing losses in our youths than they did in the past. In addition, normal aging eventually causes impaired hearing (i.e., presbycusis), and consequently the natural decrease in hearing sensitivity as people get older also needs to be factored into such surveys which often it is not. Whatever the outcome of this argument, there is no doubt that the popularity of such advances in audio technology has lowered the age at which children listen to portable music players. Thus, not only are millions of adults of all ages potentially at risk for developing recreational NIHL due to over-exposure to digital music players, but young children are too, especially if they are listening at high volumes for long periods of time.
Scientists once thought that the pure energy of loud sounds caused forceful mechanical vibrations in the inner ear that directly damaged the receptor cells for hearing called hair cells, because of their fine hair-like projections. The microscopic hair cells located in the inner ear’s fluid-filled, coiled cochlea are sensitive cells that convert acoustically induced vibratory energy into electrical signals that are inter- preted by the brain as understandable sounds. It is likely that such mechanical trauma does tear hair cells apart with a one- time exposure to sudden, very intense sounds like those asso- ciated, for example, with an explosion. However, more recent research on habitual sound exposure has shown that more typical exposures to loud sounds gradually initiate the for- mation of harmful molecules inside the ear that eventually damage or destroy hair cells by building up toxic waste prod- ucts. The destructive products are known as free oxygen rad- icals or reactive oxygen species. Such toxic molecules are formed after the cochlea’s hair cells are stressed by noise- induced reductions in blood flow, excessive and deadly levels
16 Acoustics Today, October 2007