Introduction

The development of studies in both the national and internationally occupational health arena has been decisive for the implementation and update of rules and norms that regulate many aspects of labor relations and conditions. Similarly to other areas of knowledge, studies continue to search for knowledge, interfere to favor changes, and maintain a dynamic process. However, laws and norms only reach their purpose if followed by the appropriate enforcement.

The purpose of the present study was to examine the practice of initiatives directed to prevention of hearing loss, including discussion about the labor legislation related to prevention of risks and daily application of its concepts. We intended to detect flaws that might negatively interfere in performance and analysis of our professional activities, as well as to direct them to more effective practices. We used the translation of the questionnaire proposed by the National Institute of Occupational Safety and Health (NIOSH), American institute responsible for defining occupational health policies and how to prevent work-related diseases, in the publication Preventing Occupational Hearing Loss - A practical guide (1996). The original questionnaire is online at the website : http:/www.cdc.gov/niosh/topics/noise/noisesolutions/hearingchecklist.html.

The translated questionnaire can be found in Cavalli (2002). It comprises many different aspects about theory and practice of hearing loss prevention programs (HLPP) and it was directed to occupational physicians, engineers or safety technicians involved in these programs. NIOSH proposed that this material or other similar ones be used annually to conduct auditing of preventive programs and to identify weaknesses and issues that require further remediation.

Labor legislation and Hearing Loss Prevention Programs (HLPP)

Even though it is argued that the main objective of hearing loss prevention programs is to preserve workers' hearing by creating a work environment that is healthy and safe, and not only to comply with governmental regulations and/or reducing cost of labor indemnifications, we should recognize that the legislation is a powerful driver for the existence of these programs (NIOSH, 1996).

In Brazil, the Labor Department approved in 1978 the Administrative Rule 3214 concerning Regulating Norms (NR) of chapter V, title II, of Consolidation of Labor Laws, related to occupational health and safety. The legislation aimed at ensuring preservation of health of workers, as well as the identification of occupational risks so that preventive measures could be taken in a systematic and continuous fashion.

There are 29 Regulating Norms and they address specialized services in safety engineering and occupational medicine (NR4-SESMT), accident prevention internal commission (NR5-CIPA), personal protective equipment (NR 6- EPI), occupation health medical control programs (NR7 - PCMSO), and prevention of environmental risks (NR9-PPRA), unhealthy activities and operations (NR15) or dangerous works, specific outdoors or underground activities, activities with explosives, etc, as well as inspection and penalties.

HLPP in Brazil is provided by NR9 and Annex I of Chart II of NR 7 of the Labor Department, and the topic was subdivided in the present study according to the items included in the data collection instrument. It is important to point out that NR9 states that all workers and institutions with workers shall prepare and implement a HLPP, aiming at preserving health and integrity of workers. This program should be part of other medical control programs (PCMSO).

NIOSH (1996) advocated that before putting HLPP into practice, or before changing the current HLPP, an audit should be performed. The audit shall cover:

checking whether the rules of HLPP are being complied with and are known by all those that manage or participate in the program;

 indicate a responsible person for the implementation of the program;
 define the role of supervisors;
 discuss risk assessments;
 create methods for the assessment of risk measurement results;
 identify the priority measures to be taken, as well as their frequency;
 discuss about types or auricular PPE to be used;
 assess administrative and engineering controls to be made and the definition of priorities;
 determine frequency, methodology and topic of training sessions.

Couto & Santino (1995) also indicated the need for review and periodical reassessment of HLPP in order to correct possible gaps and prevent mistakes from relying too much on the existing program.

Historically, a good HLPP consists of 7 identifiable elements: monitoring of auditory loss, administrative control, engineering control, audiometric assessment, personal auditory protective equipment, education and motivation, data storage. One more element is assessment of the program, which has been added. Considering that all elements of the program are essential to prevent hearing loss, the addition of one more element is specifically related to a process of program assessment to ensure efficiency.

Material and Method

In the present study we interviewed professionals from Occupational Safety and Medicine from industries in Curitiba and the metropolitan region, involved in hearing loss prevention activities.

Our sample comprised 30 plants, being two graphic plants, 4 food industries, 3 metallurgic facilities, 3 automotive industries, 7 wood application plants, 4 ceramic plants, 1 beverage plant, 2 chemical facilities, 1 miscellaneous manufacturing plant, 2 bagging facilities, and 1 manufacturer of electronic components. They were small, medium and large-sized companies with number of employees that ranged from, 60 to 1,718 workers, risk level of 2, 3, and 4, maximum noise level of 81 to 124 dB HL, recorded by HLPP in the companies. Out of the total, 50% reported they had an implemented HLPP. We recorded the number of effective workers, level of risk and level of noise because these factors determined the companies' legal obligations. The interviewed personnel were occupational physicians, engineers and safety technicians. The identity of the company and the interviewees was maintained confidential. In some cases, when one subject was not capable to provide responses about some stages of the program, more than one professional was interviewed. The total number of interviewees was 34, for a total of 30 studied companies. The interviews were always conducted by the author of the study, who applied the questionnaire in each company.

Script of the Interview

The tool used as interview script was a Portuguese version adapted from the NIOSH questionnaire (1996) for HLPP. The instrument comprised 69 questions. The original questionnaire is available online at http:/www.cdc.gov/niosh/topics/noise/noisesolutions/hearingchecklist.html. Owing to the method chosen to record and analyze the collected data, it was necessary to divide some questions in more than one item, and new questions were added for cases in which the answer was neither "yes" nor "no", but rather "other". The answer "other" was associated in open-ended questions. Our instrument gathered 178 questions, divided into 8 topics. The translated questionnaire is available at Cavalli (2002).

Upon analyzing the data obtained, we tried to evidence whether specific prevention measures were meeting the legal requirements in force and scientific recommendations presented by NIOSH Guide (1996), and if not, what were the obstacles for the adoption of the preventive measures.

In order to evidence whether the participating companies in the study complied completely, partially or did not comply with the requirements of the labor legislation, we divided them into two groups: companies that reported they had HLPP and companies that did not. Each group comprised 15 companies. The issues were also subdivided into 3 groups, whose topics were: meet the Brazilian labor legislation, exceed them, or do not apply to any of the previous cases.

We used Fischer exact test (Siegel, 1981) to determine the level of significance of the difference between the answers in both groups.

Results

The results obtained were complied and analyzed according to the topic described.

In the results we identified strengths and weaknesses in hearing loss preventive measures adopted by the company as a result of exposure to loud noise (with or without effective HLPP). Next, we present them according to the topic of the questionnaire. We are going to show only Table 1 so that we can demonstrate how data were tabulated; the other tables will only be briefly summed up.

Training and Education

Table 1 shows answers of interviewees about the many aspects concerning training. There was no statistically significant difference between companies with HLPP and companies without it concerning labor legislation. Only in the item that referred to assessment of the success of training programs we observed statistically significant difference (p=0.004) between responses in the two groups: companies with HLPP demonstrated they were more concerned about the topic.

Involvement of the supervisor

Most of the answers to this question demonstrated that supervisors received instruction and specific training to follow up use and preservation of hearing PPE of their subordinates, but not always are they trained to solve specific problems with workers that fail hearing tests or resists to wearing PPE. Disciplinary measures in case of workers that do not wear PPE are adopted by most companies.

The groups had statistically significant difference (p=0.01) in answers to this item about transmission of information to supervisors about use, control and preservation of PPE. The companies with HLPP are the ones that delegate this function to supervisors and support them.

Noise measurement

Most of the answers indicated that environmental noise was measured, and objectives were clearly specified, people were notified that they were exposed to risk, noise maps were used by the right professionals, and the data were consider when some worker was reassigned to a new position, but not when considering the acquisition of new machinery or change in company layout (even though it would be followed by measurement). As to registration of measurements in the medical follow-up of workers, changes in the area, equipment or production processes and measures to include or exclude workers in HLPP, we observed equivalence between positive and negative answers by both groups. In general, the answers proved to be negative to transmission of the results about noise measurements to the supervisors or its registration in the chart of each measured area.

We observed statistically significant difference in answers about transmission of results of noise measurements to supervisors and key players (p=0.01) and about registration of these data to medical control of workers (p=0.0092): most of the companies without HLPP did not adopt these actions. We also observed statistically significant difference (p=0.04) in existence and use of noise maps: companies with HLPP demonstrated they used this resource the most.

Engineering and administrative control

Most of the answers indicated that workers and supervisors were asked about many alternatives to control noise, collective noise control measures were taken using internal or external consultants, workers and supervisors received instructions about operations and maintenance of devices to control noise, and there was a meal or resting area that was quiet. As to focus on cost-benefit of many noise control options, monitoring of projects to control noise and dissemination of information about plans of control, positive and negative responses and/or others were balanced in both groups. The answers proved to be negative concerning prioritization of collective measures of noise control and assessment of maximum potential of administrative controls. As to the issue on noisier processes implemented in shifts with fewer workers exposed, the most common response was "Other", justified by the fact that there was one single shift or shifts with the same number of workers.

In the questions that concerned labor legislation, we observed statistically significant difference between the groups only in those that addressed prioritization of engineering measures (p=0.0002) and the information of workers and supervisors about the noise control measures (p=0.02).

Among the questions whose topic exceeded the labor legislation, we observed statistically significant difference in those that required cost-benefit analysis of the many options of engineering or administrative measurements of noise control (p=0.002) and assessment of maximum potential for administrative control (p=0.03): most of the companies without HLPP did not collect this type of data.

Audiometric monitoring and maintenance of records

The answers of interviewees about audiometric monitoring and maintenance of records showed that most of the answers indicated that the professionals who performed audiometry were dully trained to do so, conducted detailed and valid tests, instructed the workers and recorded the results in a complete and correct form, documented all actions, maintained records indicating calibration of audiometer according to the procedure, compared current audiograms with the baseline exam to indicate tendency of auditory deterioration in subjects and groups of workers. Most of the interviewed companies indicated other answers to questions on investigation of the reasons for inconsistency in audiometry, annual incidence of significant shift in thresholds greater than 5%, identification of problematic areas and remediation measures taken, and corrective actions in cases in which the number of absences to audiometric test was higher than 5%. Answers were negative concerning documents about level of background noise in the audiometry room, communication of results of audiometric tests to supervisors and managers and to employees, and notification in writing to workers that had significant change in thresholds within a period of 21 days.

Referrals

Most of the companies reported that the procedures related to referral of employees, for complementary tests or treatment, were well defined, clarified, followed up and documented.

Personal protection equipment

Most of the answers to these questions were positive concerning offer, available variety, adaptation directed to comfort, training, checking, reposition, problem resolution, assessment of efficacy of PPE. Most of the answers were negative to acquisition of ear infections resulting from hearing PPE use, occurrence of cases in which the equipment was contraindicated, complaints concerning interference in skills to perform the work, communication or warning signs and instructions about use of PPE in extra-occupational noisy activities. We found equivalence of answers between the groups in assessment of attenuation level of auricular protectors and documentation about the results of training sessions on PPE use given to workers.

Administrative issues

Most of the answers indicated that HLPP policies have been modified to reflect the changes in legislation, that subjects that implement elements of the program were aware of the policies and complied with them and their performance was periodically assessed, and that the purchasing department did not negatively interfere in the orders requested by the implementation responsible person, and records of accidents resulting from impossibility to hear shouts or warning signs owing to use of auricular PPE. However, the answers were negative concerning dissemination of the program policy.

We observed statistically significant difference (p=0.01) between the groups only in the question about adaptation of HLPP policies to changes in Brazilian legislation.

In this graph we can see that answers of both groups of companies presented few variations and even companies that referred they had HLPP did not totally comply with legal requirements, a fact confirmed by the individual statistical analysis of each answer already described.

The chart that follows presents a summary of the results obtained with the interviews. The groups with and without HLPP were not separated since we did no detect statistically significant difference between them.





Discussion

In the studied companies, even in those that reported they had effective HLPP, we observed that the measures adopted for hearing loss prevention were part of other safety programs. These companies did not have structured documents with formal determination of program steps nor formal key-person responsible for implementing and coordinating the procedures. They did not disseminate the actions to the involved parties. It compromises the compliance with legal requirements since without coordination of actions and involved sectors, there is no guarantee of enforcement of necessary measures to reach the objectives.

We also observed that as the interview went by, if the interviewee identified any gaps in the procedures, many times they reported corrective measures they intended to adopt, demonstrating some degree of concern about providing positive responses. The participation in this study allowed them to approach people involved in the program, which reflected the poor interaction between them, emphasizing the lack of appointment of a responsible person to coordinate the program and the measures adopted to prevent hearing loss.

Next, we will discuss the results of this study, also according to the topics of the questionnaire proposed by NIOSH (1996).

Training and Education

In our study, the interviewed parties reported that training and instruction were provided at least once a year (in orientation and at SIPAT). We detected cases in which training was conducted only when the new employee was going through orientation. This training session addressed explanations about internal norms of work safety, in addition to explanations and demonstrations about the use of many different equipment and individual protection devices (not only hearing protection); workers, however, did not have to individually show that they knew how to correctly manipulate the equipment. Therefore, they have to register the understanding of information and necessary equipment, in addition to creating strategies to make sure that the employee has really understood the information and knows how to put it into practice.

SIPAT (work-related accident prevention week) addresses topics related to hearing loss, but the participation of workers in these events is variable, depending on superiors authorization and demand of production.

In general, individual instruction is provided only in cases in which the worker comes to the Occupational Safety department to ask for help because of problems with PPE. This area is not informed about the cases of audiometric worsening because as most interviewees stated, these data are not checked nor disseminated, since they only consider presence or not of hearing loss. Even cases of hearing loss detected by the medical department are sometimes not informed to the occupational safety and engineering department.

According to NIOSH (1996) and Fiorini & Nascimento (2001), effective HLPP requires employers and managers to be trained and have educational experience, but our questionnaire did not focus on top management involvement. As to the involvement of supervisors, some interviewees said that many participate actively in these programs, whereas others do not. They also reported that some participate partially, concerning training and information passed on to subordinates.

Labor legislation in place in Brazil emphasizes the need to implement training programs directed to workers, but it does not define planning or execution strategies.

Involvement of supervisors

In the present study we observed that there are companies that do not designate supervisors to have prevention of hearing loss as a task, which can be evidenced by the fact that not all of them use the appropriate PPE at the right site. The measures adopted by supervisors are to refer all complaints and detected problems, such as discomfort, auricular pruritus, inappropriate use or failure to use PPE, directly to the department of Occupational Safety to be solved. Companies fail to use important instruments, especially owing to closeness and daily contact between supervisors and workers for the success of hearing loss prevention measures.

This topic is not approached by the labor legislation in place, which only alludes to legal obligations of employers and specific areas, such as SESMT and CIPA. Apart from that, supervisors are limited to receiving the same training sessions and information provided to other workers, and their effective participation is basically on the internal norms of the company.
The companies referred that they adopted disciplinary measures in case of resistance to use auricular PPE. Labor legislation states that this device should necessarily be used in companies in which there is excessive noise, but it does not refer to mechanisms to make it happen (instructions, notifications, verbal or written advice). NIOSH warns to the fact that the adoption of punishment or rewards rarely ensures good results, except when they are generated by initiative of the workers (NIOSH, 1996).

Noise measures

In the studied companies we observed that noise measures were made at least annually and many times the execution of the service was delegated to a third-party company. They used sound pressure meters (without filter for octave band, practically unknown), and less frequently, dosimeters. The data generated by these measures were used to prepare HLPP.

Despite the existence of auricular PPEs with record of attenuation by frequency range, NR7 refers that the maximum noise level acceptable in audiometric booths should comply with the disposition of Norm ISO 8254-1 (by frequency range) and NR9, containing the maximum level of allowed noise for exposure of workers shown by frequency ranges, and we did not find any regulating norm that referred to measurement of environmental noise by the same criteria. This measurement can be obtained by means of a filter of octaves and third of octaves, characterizing the detailed sound spectrum, which will facilitate the selection of effective measures of noise control.

As to data concerning measurement of noise, we observed that the company recorded them in the HLPP but informed the results only upon request, and to some supervisors. There are noise maps containing only the level of noise and no specific values for range of intensity.

The legislation in place - specifically Annexes I and II, NR 15 (Administrative Rule 3214), does not completely described the correct methodology for the acoustic analysis of industries: it restricts to the definition of concepts, describing the regulation of equipment to the specific measurements, such as compilation and classification of expected results without explaining how to obtain, interpret, judge, report, or disseminate the records, nor what measures should be taken to as a result of the data collected. The labor legislation is not directed to determining as professionals trained in SESMT and/or collaborators should execute the tasks relevant to them, but rather to determine minimal guidelines for the standards to be followed, preventing different interpretation, facilitating inspection and ensuring that the proposed goals are respected.

Engineering and administrative control

Regulating Norms and the scientific community recommends prioritization of engineering and administrative control measures to harmful exposure, but it is not very specific on how to do it, leaving the decision to the top management of companies. Cost-benefit is not focused or clearly assessed. Fundacentro (1999) for example, provides that we should primarily search for solutions to control noise source; as the second alternative, control noise path, and the third option, as definite control where there are no technical solutions that are implementable or viable to the source or path control, then the use of auricular protectors is recommended. In this study, most companies reported that they did not have collective measures to control noise under study or to be implemented, nor projects for its execution.

Many interviewees referred that noise control measures at the source were suggested by SESMT, but the approval depended on top management decision. Many studies were not approved owing to their very high cost. We did not observe any project in execution to control noise at the source.

Administrative measures to control noise implied efforts to limit exposure to noise by making changes to the work site or time or modifying the machine operation time, in addition to allocating areas, rest and meal rooms, where workers could be away from noisy environments. The companies referred that they had those quiet areas away from the plant. We did not detect any company that adopted noise control administrative measures.

Audiometric monitoring and maintenance of records

Let us analyze this item according to the elements that should be checked to reach audiological management.

To determine the test environment, subjective criteria have been used, or in other words, the site should be apparently quiet. Some interviewees said they used sound pressure meter without octave band filter. There were no documents that record sound levels in the test room.

In the present study we did not ask the brand or model of equipment used to assess hearing; therefore, we do not have data whether they meet the scientific specifications or not. NR7 does not make any demands concerning the device used. As to calibration of equipment, we learned that annual partial acoustic calibration was made and recorded in audiometric records. Companies do not have copies of the calibration certificates. Biological and electroacoustic calibrations were not questioned.

Audiometric tests were conducted with hearing rest period longer than 14 hours, which does not allow detection of temporary thresholds shifts, but rather only permanent ones. Considering prevention, detection of hearing decrease while it is temporary provides the adoption of measures to prevent it from becoming permanent. It implies review of preventive techniques currently adopted in Brazilian industries, since the legislation requires that the tests be conducted after acoustic rest. The interviewees reported that they were not familiarized with the methodology of auditory assessment and that the audiologists were responsible for performing the tests and could give all information about them. They demonstrated that they did not have information about temporary threshold shift.

Preventive measures, which should use the data provided by the audiometric follow-up, were not adopted. The level of permanent threshold shift was not known by the interviewees.

Referrals

In the studied companies, referrals were suggested by the person responsible for the audiometry (which could be motivated by removal of earwax, otological diagnosis and/or opinion about audiometric worsening), and normally directed to the occupational physician to refer them to the Otorhinolaryngologist, at his/her own discretion, since if the problem was solved there, or if the worker already had the diagnosis, the referral may have been ignored. The ENT examination and the results were filed in the medical chart of the employee.

Procedures for referrals range from company to company. We did not gather data that indicated that the suggested referrals were actually made.

Personal protective equipment

NIOSH (1996, 1998) emphasized the importance of having a comfortable protector that did not prevent communication, maximizing the duration of use. Owing to that, we should provide to each subject a wide range of protectors so that they can select the one that is the most comfortable and also avoid protectors that provide greater attenuation than necessary. There were two options provided in some companies: insertion plugs and complete earphones, a range that limits the selection of workers.

The issue of financial investment in prevention measures can be seen from a mid and long-term perspective, since acquisition of quality auricular PPE and sufficient variety for the worker to choose, systematic replacement, hygiene procedures and continuous training can be apparently costly, but it is in fact cheaper than other forms of noise control.

Administrative issues

The category of administration includes all those in the position to prepare or enforce a program and authorize allocation of resources. The responsibility of these participants should be clearly identified by the program.

Most of the interviewees observed that the company management had limited participation. The administrative area had provided, depending on cost, acquisition of materials and execution of the necessary works for noise control, according to the requests made by SESMT.

This area is informed of activities related to hearing protection, but they are not committed to the objectives of the program.

Criticism on the tool used in the study

The time used to apply the questionnaire ranged from one to two hours, and in most cases it was enough to interview one person only. The division by sessions facilitated the approach of each topic and the collection of specific answers to each step of the preventive program. The use of an interview script such as this one may facilitate the work of professionals involved in prevention of hearing loss and the recognition of weaknesses in initiatives and corrective measures adopted. If used periodically, together with comparison of audiometric results, it can provide important information about the evolution of the initiatives made.

However, upon using the script proposed by NIOSH (1996), we observed some problems that the tool has:

 very long questions, requiring more than two answers;
 subjective questions that do not elicit the expected answer;
 questions are not prepared according to the Brazilian labor legislation, which hinders the classification of answers, such as the ones that exceed the legal requirements and those that do not apply to our cases, since they are specific situations of the companies.

To better understand the interviews, we should adapt the above-referred items.

Conclusion

The purpose of the present study was to examine the practice of initiatives directed to prevention of hearing loss, including the discussion about Brazilian labor legislation related to risk prevention and daily applications of the assumptions. We also aimed at detecting flaws that may negatively interfere in the performance and analysis of our professional activities and direct them to more effective actions.

Based on the data obtained, we concluded that concerning compliance with labor legislation referring to hearing loss prevention measurement, there is no statistically significant difference in management style between the two groups (those with and without HLPP), and that none of them complied in full with the legislation in placed. It indicates that industries with the program are not very different from the others that do not have it.

Considering working conditions, noise exposure is only one of the main items under responsibility of SESMT. In view of that, there is the need to create and use mechanisms of assessment and control of programs related to workers health.

The use of a script facilitates the checking of HLPP and the detection of weaknesses. We should, however, prepare a model based on Brazilian labor legislation with clear and objective questions, whose answers can really reveal compliance or not with actions of the program.

References

1. BRASIL. Portaria nº 24, de 29/12/1994 - NR 7 - Programa de controle médico de saúde ocupacional (DOU 30/12/1994).
2. BRASIL. Portaria nº 25, de 29/12/1994 - NR 9 - Programa de prevenção de riscos ambientais (DOU 30/12/1994).
3. BRASIL. Portaria nº 26, de 29/12/1994 - NR 6 - Equipamento de proteção individual - EPI (DOU 30/12/1994).
4. BRASIL. Portaria nº 33, de 27/10/1983 - NR 4 - Serviços especializados em engenharia de segurança e em medicina do trabalho.
5. BRASIL. 08/06/78 - NR 15 - Atividades e operações insalubres.
6. Cavalli RCM. Avaliação das práticas para prevenção de perdas auditivas em indústrias de Curitiba e região metropolitana; 2002, Universidade Tuiuti do Paraná, Curitiba; 2002; p. 1-62.
7. Couto H De A, Santino E. Guia prático: audiometrias ocupacionais. Belo Horizonte: Ergo, 1995.
8. Fiorini AC, Nascimento PES. Programa de prevenção de perdas auditivas. In: Nudelman AA et al. PAIR: perda auditiva induzida pelo ruído. Rio de Janeiro: Revinter, 2001. v. 2, p. 51-61.
9. Fundacentro. Ministério Do Trabalho E Emprego. NHO 01. 1 ed. Brasília, 1999.
10. National Institute for Occupational Safety and Health, NIOSH. Criteria for a Recommended Standard - Occupational Noise Exposure - Revised Criteria 1998. U.S. Department of Health and Human Services - Public Health Service - Centers for Disease Control and Prevention.
11. National Institute for Occupational Safety and Health, NIOSH. Preventing occupational hearing loss - A pratical guide, Edited by John Franks, Mark R. Stephenson, and Carol J. Merry June 1996/ Revised October 1996. U.S. Department of Health and Human Services - Public Health Service - Centers for Disease Control and Prevention.
12. Siegel S. Estatística não-paramétrica: para as ciências do comportamento. São Paulo: McGraw-Hill do Brasil, 1981. p. 107-16.

1 Speech Therapist, specialist in Audiology, Master in Communication Disorders.
Speech Therapist, Ph.D. in Communication Disorders, post-doctorate studies in Occupational Collective Healthcare.
Professor, Master in Geodesic Sciences, Ph.D. in Geodesic Sciences, University Tuiuti, Parana.
Address correspondence to: Regina C.M. Cavalli - Rua Mário Jordão Afonso da Costa, tv. 200, casa 04. Jd. Esplanada, Curitiba PR 80740-190.
Tel (0xx41) 3018-6683 ou 9984-7196 - Fax (0xx41) 244-1907
Presented at VIII Encontro Internacional de Audiologia, April 11-13, 2003, Curitiba, PR
Article received on September 23, 2003. Article accepted on April 29, 2004.