Potential health risks of exposure to noise from personal music ...

Health risks from exposure to noise from personal music playerset al. 1998, Giraudet et al. 2002), and NMDA blocking agents (Chen et al. 2003, Diao etal. 2005, Ruel et al. 2005).MiscellaniousHypothermia (Henry 2003), prior heat acclimatation (Paz et al. 2004) and a heat shockprotein inducer (Mikuriya et al. 2005) were reported to protect from NIHL, as were alsoATP (Sugahara et al. 2004), NO inhibitors (Xiong et al. 2002, Ohinata et al. 2003) and acalcium pump activator (Liu et al. 2002). A special reference must be made tomagnesium treatment which was found repeatedly protective (Scheibe et al. 2001,Scheibe et al 2002, Haupt et al. 2003, Attias et al. 2003 , Sendowski et al. 2006b).3.5.5. Clinical evaluation of noise damage3.5.5.1. Hearing lossNIHL refers mostly to deafness, the inability to hear certain sounds, but this hearing lossis most often associated with considerable difficulties in auditory discrimination ofsimultaneous sounds, such as speech understanding in a noisy environment, whichaffects notably social interactions. In addition NIHL is often associated with tinnitus whichmay also be very damaging to a person’s living, and sometimes also with hypersensitivityto loud sounds. Overall NIHL has a noxious socio-economic impact for both the affectedperson and the society in which he lives. The noise-induced auditory impairments aremost often progressive and insidious, they begin at high frequencies with only slightdisturbances hardly perceptible which usually disappear within some time after noiseexposure and so they are almost always neglected. However, over time and repeatedexposures these troubles progressively increase to become a patent nuisance, but thenphysiological damages to the ear are almost always irreversible and at present quasiincurable.Subjective audiometryNIHL is evident on the audiogram as mild or moderate bilateral sensory (cochlear)hearing loss, predominantly at high frequencies. The greatest hearing loss is commonlyat 4 kHz, giving rise to the typical 4 kHz notch in the audiogram pattern (Alberti 1977).Although the notched audiogram is the most specific audiometric feature of NIHL, recentstudies re-emphasized that caution should taken to this feature as it can be seen in earpathologies of other causes and that a significant number of NIHL do not show a notchedaudiogram (Murai 1997, McBride and Williams 2001, Schmuzigert et al. 2006).In line with previous studies several articles confirmed that very often in NIHL acousticsensitivity at the very high frequencies (which are not measured in usual audiometry)shows deficiencies starting earlier than at other classical frequencies (Wang et al. 2000,Ahmed et al. 2001, Schmuzigert et al. 2006).It was also confirmed that NIHL due to impulse sounds such as firearms shots produceon average more loss at high frequencies and may have longer-lasting effects(Schmuzigert et al. 2006, Tambs et al. 2006).Although hearing losses appear stabilized over years it may continue to progress andaffect lower frequencies (Gates et al. 2000, Brickner et al. 2005). The loss of sensitivityfor quiet sounds is accompanied by a loss of frequency resolution which then affectsspeech recognition. Typically, people with NIHL complain of loss of perceived clarity ofspeech and greater difficulty than normal following speech in a background of noise.Objective audiometryAuditory-evoked potentials can be useful to monitor and/or ascertain NIHL. Past studiesusing late cortical potentials and brainstem potentials were forsaken in recent years (only34