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

Health risks from exposure to noise from personal music playersear-bud in the ear canal, the volume setting of the device, the maximum output providedby the particular device and ear-bud combination and lastly the type of music. In theworst case scenario, it is possible to estimate maximum levels of about 120 dB(A).3.7. PMP usage in the populationIn the last decade PMPs have become used by an increasing portion of the population.The maximal levels of noise produced by the new generation devices are very high andobviously cause an increased risk of hearing impairment. The factors involved in thepotential risk of hearing loss are noise intensity and duration of exposure at a particularlevel. Listening environment, type of headphones / earphones as well as type of musicmay play additional roles. This chapter describes the habits of listening to music throughPMPs on a regular basis by teenagers, as well as the availability of PMPs. The dataprovided in this chapter are crucial for a risk assessment.3.7.1. Listening levelsSeveral studies are accessible in the literature assessing PMP in terms of maximumsound pressure level measured in dB SPL or dB(A). Already Katz et al. in 1982 warnedthat stereo earphones could deliver acoustic levels up to 120 dB(A) (Katz et al. 1982).Later in 1985 Lee et al. measured portable headphone cassette radios peak outputs of 90to 104 dB (Lee et al. 1985).Rice et al. examined over 60 users of personal cassette players (PCP). They were askedto set the volume control of a PCP to the level at which they would normally listen todifferent types of music. The ranges of measured sound pressure levels were between 60and 108 dB(A). Mean free-field equivalent continuous A-weighted sound pressure level(unobstructed field L Aeq ) was close to 85 dB L Aeq , 25% of the sample experienced levels ofat least 90 dB (A), and 5% had levels above 100 dB(A) (Rice et al. 1987a).In the study by Wong et al. the equivalent measured music noise levels were of 56 to116 dB(A) among 394 PMP users (Wong et al. 1990).In the study by Turunen-Rise et al. published 16 years ago, A-weighted maximum andequivalent sound pressure levels (SPLs) were measured on KEMAR (Knowles ElectronicsManikin for Acoustic Research) system on five different PCPs while playing selected typesof music and using different gain (volume) settings. The types of music included popmusic, classical music and light classical music. The transformed A-weighted fieldequivalent SPLs were on average from 75 to 85 dB(A) only (Turunen-Rise 1991).In the study by Ising et al. sound levels of music played from mini-cassette players viaheadphones were measured in a nonrepresentative group of 681 pupils whose ages werebetween 10 to 19 years. They set music levels measure as free field corrected short timeLeq, between 60 dB(A) and 110 dB(A) (Ising et al. 1994).In a study of social noise in a population sample of representative 18-25 year olds in theUK Smith et al showed that the level of preferred listening on PMP was 74 dB(A) whichwas 72.6% in the low noise category and 80.3% in those with significant social noiseexposure. In the tail of distribution it was found that 6.9% adjusted to levels in excess of90 dB(A). If adjusting for enjoyment then the average level of adjustment in a quietroom was 85 dB(A) with a mean of 92 dB(A) in those who had significant social noiseexposure (Smith et al. 2000).The availability of portable high-performance digital players, with an increased dynamicrange, has facilitated the listening to music at high levels due to reduced distortion atthese levels. Some measurements point to the fact that very high acoustic levels couldbe reached (125-127 dB(A)) with a L equ, 1h of 110 dB(A) (Loth et al. 1992). The study byFligor and Cox published in 2004 indicated that for several different styles ofheadphones/CD players, free-field equivalent sound pressure levels measured at42