BMC Public Health 2008, 8:151 http://www.biomedcentral.com/1471-2458/8/151 Background Music is ever present in our daily lives, establishing a link between human beings and the arts through the senses and pleasure. However, if we use music inappropriately, that is, if we make abusive use of the duration, intensity and/or frequency of exposure to music, the noise may have an adverse impact on our hearing function. High frequency of hearing loss consistent with noise exposure (noise-induced hearing loss, NIHL), excluding cases of acute acoustic trauma, is characterized by the gradual and progressive loss of hearing acuity. NIHL occu- pies the second place among the most common hearing illnesses, only surpassed by presbyacusis [1,2]. In Brazil, noise has only been recognized as an ambient pollutant since March 1991 [3]. Epidemiological data regarding hearing loss in Brazil is scarce and only relates to certain fields of activity. Thus, there are no epidemio- logical records characterizing the real overall situation. The data on the prevalence of hearing loss that are availa- ble provide a partial picture of the risk associated with this condition. It has been estimated that 25% of the worker population exposed to noise have some degree of NIHL. In spite of being the most frequent type of damage to workers' health, the prevalence of NIHL among Brazilian workers is still unknown [4]. In the United States, approximately ten million workers have NIHL > 25 decibels (dB) [5]. In the United Kingdom, NIHL was the second most frequent workplace-related ill- ness officially recorded in 1990 and 1991 [6]. According to data from the World Health Organization (WHO), approximately 16% of the world's population endures NIHL caused by occupational exposure to noise [5]. NIHL is generally sensorineural, bilateral, symmetrical and irreversible. Individuals with this illness are likely to present a prolonged history of exposure to high noise lev- els (> 85 dB(A) for eight hours a day), sufficient to have caused a loss in the levels and configurations observed in audiological tests. Hearing loss consistent with noise exposure is likely to have gradually developed over a period of between 5 and 20 years of general exposure in all locations [7,8]. Recently, there has been rising concern about the preva- lence of NIHL caused by excessively amplified sound activities in leisure settings. Among these activities, the exposure of musicians and sound technicians (profession- als involved in sound mixing, microphone operation and video material editing) who are exposed to intense and long lasting music have been highlighted. With regard to sound technicians who begin their careers early in life and consequently are frequently exposed to high-intensity sounds, it needs to be asked how the hear- ing levels of these individuals are holding up, when music is the medium through which they perform their profes- sional activities. Sound technicians are the agents who transport to con- sumers one of Brazil's best products: Brazilian popular music. Dealing with and watching over what this process entails is of great social relevance to the country's health, culture and economy. Moreover, decreases in hearing function worsen individu- als' quality of life, communication abilities, educational achievements and enjoyment of leisure activities, and have enduring economic consequences [9]. Thus, the present study had the aim of gauging the preva- lence of high prevalence hearing loss consistent with noise exposure among sound technicians and comparing this with a control group without occupational noise exposure. Methods This study was approved by the Ethics Committee of the Federal University of São Paulo. It was a cross-sectional comparative study between two groups: sound techni- cians and individuals without occupational noise expo- sure (controls). The sample consisted of 177 participants: 82 people working with sound systems and a sample of 95 members of the general population (control group). The inclusion criterion was that participants needed to be adults > 19 years old. The sound technician group included professionals involved in sound mixing, audio equipment operation, video material editing, video equipment operation and microphone operation, working in closed or open spaces, with at least five years of exposure to sound-producing activities [7,8]. The control group consisted of individuals without a his- tory of exposure to continuous noise, i.e. individuals who were rarely exposed to music and whose work activities did not involve music. Workers exposed to high levels of industrial noise, such as factory workers, bus drivers and the like, were also excluded from this group. The following were exclusion criteria for both the sound technician and control groups: use of individual sound amplification devices (hearing aids); diagnosis of congen- Page 2 of 8 (page number not for citation purposes)