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

Health risks from exposure to noise from personal music playersby exposure to aircraft and road-traffic noise and speech noise at 66 dB(A) L equ during 15min exposure time while reading a text and tested for memory of the text an hour lateror a week later. For aircraft noise there was impaired memory also from 15 min exposureto 55 dB(A) L equ .For chronic aircraft noise exposure the Munich study (Hygge et al. 2002) and the RANCHstudy (Stansfeld et al. 2005) indicated that children exposed to chronic aircraft noiseshowed cognitive deficits compared to children not having been exposed to chronicaircraft noise. It was also found that the children at the old airport in Munich, who got ridof aircraft noise, improved their cognitive performance. Thus, there was somereversibility in the negative effects of noise on cognition when the noise ceased. To whatextent this recovery is dependent upon the age of the children in question (11-12 years)and the accompanying continuing growth in cognitive development, we do not know.Thus, short time exposure (15 min) to noise with average levels of 65 dB(A), impairsmemory and learning. Long-time chronic exposure to, at least aircraft noise, indicate thatthere will be statistically significant impairments of memory and language skills when thenoise levels increase from around or below 55 to above 60 dB(A) L equ .3.9.1.2. Attention and distractionUse of music is sometimes employed to distract from a noisy working environment, andsometimes this is beneficial. One reason for this to happen is that the more boring,repetitive and simple a task is, the more will it benefit, both in quality and quantity, frombeing performed in noise (Kryter 1994). On the other hand, the more complex anddifficult the task is, the more it is prone to be hampered by excessive sounds.When the noise is preferred music from PMP one would in addition expect more of aperceived comfort. Further, when the music from the PMP also masks distracting soundsin the environment, devoid of relevant information or warning characteristics, it will mostlikely be a subjective advantage to listen to the PMP rather than to shut it off. On theother hand, the more cognitively demanding the task is, the more it is dependent uponspeech communication, and the more there are of potential warning sounds in the closeenvironment, the more to the disadvantage of the task performance and the security ofthe listener the PMP-listening is.With regard to attention, there is always a risk that the sound of the music listened tofrom the PMP will acoustically mask warning sounds e.g. from approaching cars, streetcrossings or reversing trucks. Even if the music is not in a physical sense masking thewarning sound, the focused attention on the music will from time to time make thelistener inattentive to other sounds, some of which my be warning sounds.3.9.1.3. School performanceThere are a several cross-sectional studies that have reported a covariation between highnoise levels (from aircraft or road traffic) and low grades or low levels of schoolachievement (Cohen et al. 1981, Cohen et al. 1986, Green et al. 1982, Evans andMaxwell 1997, Haines et al. 2001a, Haines et al. 2001b, Haines et al. 2001c, Haines etal. 2002, Maser et al. 1978, Stansfeld et al. 2005). However, cross-sectional studiessuffer from two possible short-comings. The first is the differential socio-demographiccomposition of the noise dose groups, which may favour children in quiet middle-classhousing and living areas. Adjusting statistically for the social class effects may not besufficient to control for this. The second is the possible confound between being exposedto noise both while learning and when tested for what is learnt. Noise at testing maylower the test scores without learning being effected, but the effects of noise on learningand performing can not be disentangled. Thus, cross-sectional studies are not the bestplatform for a strong inference on cause-effect relationships.56