TABLE OF CONTENTS Content Page Introduction 1 Objectives of HCP 1 Elements of HCP 1 Requirements for HCP 2 Planning for HCP 3 Identification of Noise Hazard & Evaluation of Noise Risk 5 Noise Control 9 Hearing Protection 16 Training and Education 22 Audiometric Examinations 23 Record Keeping 27 Programme Evaluation 28 Appendices 29 Appendix 1: Hearing Conservation Programme for Managing Noise Risks 30 Appendix 2: Noise Hazard Identification Checklist 31 Appendix 3: Noise Monitoring Report 32 Appendix 4: Noise Control Plan 34 Appendix 5: Audiometric Examination Form 35 Appendix 6: Certificate of Fitness 36 Appendix 7: Certificate of Suspension 37 Appendix 8: Register of Persons Employed in Work Involving Exposure to Excessive Noise 38 Appendix 9: Summary Report Form 39 Appendix 10: Hearing Conservation Programme Evaluation Checklist 41
INTRODUCTION Noise is generated by many industrial processes, operations and work activities. It is one of the most common occupational hazards. Prolonged exposure to excessive noise can cause noise-induced hearing loss (NIHL), commonly known as noise-induced deafness (NID). NIHL refers to a permanent loss in hearing sensitivity, which leads to communication difficulties, impairment of personal relationships, social isolation and degradation in the quality of life. Other detrimental effects of excessive noise exposure include tinnitus (a distressing condition characterized by ringing in the ear which can lead to disturbed sleep), acoustic trauma (temporary or permanent hearing loss due to sudden exposure to very loud noise), interference with speech communication and with perception of warning signs, disruption of job performance, annoyance and extra-auditory effects. To protect exposed employees from the adverse effects of noise, every workplace with a noise hazard should implement a comprehensive Hearing Conservation Programme (HCP), as part of the company s safety and health programme. The Guidelines on Hearing Conservation Programme serve to assist employers, plant engineers, noise monitoring and noise control personnel, safety and health officers and other stakeholders in the implementation of the HCP. OBJECTIVE OF HCP The objective of the HCP is: To mimimise the risks associated with occupational noise exposure and to prevent NIHL. ELEMENTS OF HCP The basic elements of a HCP are: 1. Identification of noise hazard and evaluation of the risks involved. 2. Implementation of noise control measures, such as engineering and administrative controls to minimise the risk. 3. Provision of suitable hearing protectors to persons exposed to excessive noise and ensuring their usage. 4. Training and educating persons involved in HCP to raise their awareness of noise hazards and their prevention. 5. Conducting annual audiometric examinations to monitor the effectiveness of HCP in preventing NIHL, and detecting early hearing impairment. 6. Keeping records on the measures taken to protect employees from noise hazards. 7. Evaluation of HCP to determine its effectiveness and areas for improvements. 1
An effective HCP can minimise or eliminate noise hazard and prevent NIHL. Strong management commitment and active employee involvement are critical for the success of the HCP. Therefore, management should take the appropriate steps to encourage workers participation in the development and implementation of the HCP. A flowchart which provides an overview of the HCP is shown in Appendix 1. ENGINEERING CONTROL HEARING PROTECTORS EDUCATION REQUIREMENTS FOR HCP Your workplace will require a HCP when: Any person in the workplace is exposed to excessive noise, which is defined as an equivalent sound pressure level of 85 db(a) or more over an 8-hr workday. 2
PLANNING FOR HCP ESTABLISHMENT OF A HCP TEAM Where it has been identified that HCP is required at your workplace, the employer in consultation with the employees, should set up a team to implement the HCP. The composition and size of the HCP team should be proportionate to the size of the company and the number of employees exposed to excessive noise. The HCP team may comprise the following: safety and health personnel, noise monitoring officer, noise control officer, industrial hygienist, industrial nurse and employee representative. The most important members of the team are the employees whose support and participation is the key to the success of the programme. APPOINTMENT OF A HCP ADMINISTRATOR Management needs to designate a programme administrator to take charge of the HCP. The role of the HCP administrator involves coordinating the HCP, monitoring its progress, assessing its performance, evaluating its effectiveness, reviewing the HCP at regular intervals, and ensuring that the set objectives are met. The HCP administrator should coordinate all aspects of the programme. He or she should possess knowledge on: Individual elements of HCP. Relevant provisions of the Workplace Safety and Health Act, the Workplace Safety and Health (Noise) Regulations, and the Workplace Safety and Health (Risk Management) Regulations. Effects of noise on hearing. Purpose of hearing protectors and audiometric examinations. The programme administrator should be an individual who has genuine interest in the company s HCP. The individual should possess good communication skills and spend time at the production floor to interact with employees and to discuss how noise problems can be prevented or solved. Management needs to provide the programme administrator with the authority to make decisions, correct deficiencies and enforce necessary actions. The programme administrator should arrange meetings or discussions to promote collaboration of effort between management and team members, and to foster exchange of information on the progress of the programme. Once the team members understand how their role contribute to the overall outcome of the programme, they will be motivated to cooperate to prevent hearing loss. DEVELOPMENT OF A HCP POLICY The employer, in consultation with the employees should develop a written HCP policy, which demonstrates the commitment of the management towards the programme. The policy should be based on effective practices rather than minimum compliance with the legislation. More importantly, the policy should be endorsed by the top management, and should as far as possible, address the following: Promoting a positive safety and health culture at the workplace where employees are empowered and motivated to protect their health and that of their fellow workers. Adopting a prescribed schedule for monitoring employee noise exposure levels and other risks, including ensuring equipment and personnel training are appropriate to the task. Setting targets for minimising daily and peak noise exposure levels in the workplace and developing strategies to achieve them. Requiring consistent and proper wearing of hearing protectors in designated areas. Ensuring the correct use of the hearing protectors through onsite inspection. 3
Educating, training and motivating employees to support the HCP; assessing employee attitude and knowledge gained from periodic training. Purchasing appropriate hearing protectors, noise measuring equipment and quieter machinery. Requiring employees who are exposed to excessive noise to undergo audiometric examinations. Counselling employees following each audiometric examination. Reviewing audiometric data to verify the effectiveness of the HCP. Establishing proper selection procedure for vendors and contractors for services which cannot be undertaken by in-house staff, such as noise monitoring and audiometric examinations. Companies that issue a clearly defined HCP policy, and follow or implement the policy will be able to implement the HCP more effectively. With a well defined policy, employees are informed of their functional role and their duties. With the formation of a HCP team, the appointment of a HCP administrator and establishment of the HCP policy, the team can proceed to implement the HCP. The sections that follow contain the details of each of the HCP elements. 4
IDENTIFICATION OF NOISE HAZARD & EVALUATION OF NOISE RISK Under the Workplace Safety and Health (Risk Management) Regulations, a risk assessment must be conducted and documented for all work activities, including noisy processes. The first phase of risk assessment involves hazard identification which can be qualitative or quantitative in nature. Qualitative hazard identification can be performed using a checklist or through site inspection. If the outcome of the site inspection suggests that noise problems exist in the workplace, the hazard should be quantified and evaluated through noise assessments. The risk assessment should be reviewed and revised at least once every three years; and upon occurrence of NIHL or significant change in work practices or procedures. IDENTIFICATION OF NOISE HAZARDS Identification of noise hazards in a workplace enables employees who may be exposed to excessive noise to be identified so that their exposures can be assessed. The hazard identification should involve the participation of the affected employees and those who understand the work processes and have knowledge of the work situation. QUALITATIVE APPROACH A noise hazard identification checklist is provided in Appendix 2 for a quick assessment to identify if noise hazards are present at the workplace. In addition, a site inspection should be carried out to identify noisy work processes, the type of noise generated (e.g. steady, fluctuating or impulse / impact noise), the persons exposed to the noise and their work or exposure pattern. When it is identified that noise hazards exist in the workplace, a noise monitoring should be conducted. QUANTITATIVE APPROACH - NOISE MONITORING Noise exposure levels should be assessed in such a manner that will accurately identify persons who are at or above the 8-hr exposure limit of 85 db(a). Measurements should also be made whenever any modifications are made to the machinery or processes that may increase the noise levels to which persons are exposed. Under the Workplace Safety and Health (Noise) Regulations, where 10 or more persons are exposed to excessive noise, a competent person must be appointed to conduct noise monitoring once every three years, or earlier when changes in conditions occur which may cause any person in the workplace to be exposed to excessive noise. Management can engage an acoustical consultant or appoint a qualified person in-house to conduct noise monitoring. The noise monitoring results should be compared with the previous report so that any significant changes can be identified and investigated. It is also important that monitoring is performed after noise control to evaluate the residual risk. 5
Objectives of Noise Monitoring All workplaces where employees may be exposed to excessive noise should perform a noise monitoring to achieve the following objectives: 1. To quantify the noise hazards. 2. To identify employees affected by the noise hazards for inclusion in the HCP. 3. To classify employees noise exposures for prioritizing noise control efforts and establishing hearing protection practices. 4. To evaluate specific noise sources for noise control purposes. 5. To evaluate the effectiveness of the measures taken to minimise noise exposure. 6. To delineate hearing protection areas. Types of Noise Monitoring The types of noise monitoring that are commonly carried out in the workplace include the following: 1. Area Surveys A sound level meter is used to measure noise levels at work areas where noise hazards have been identified. The results of measurements are normally plotted in the form of a noise map, which clearly indicates areas with sound pressure levels above the permissible exposure limit of 85 db(a). 2. Dosimetry Noise dosimeters can be worn by employees to monitor personal noise exposure over the work shift. Some noise dosimeters are able to record a time history of an employee s noise exposure for the measurement period. This allows identification of noise sources, which have a significant contribution to the employee s noise exposure level. When performing a noise dosimetry, the following points should be considered: Reflection of sound from the body may increase the noise level measured. The microphone should be attached as close as possible to the ear as inappropriate positioning of the microphone, such as at the lower part of the collar or pocket, may give rise to higher or lower readings. More measurements may be required if monitoring over a single work shift is unable to give a representative sample. 3. Engineering surveys Engineering surveys involve the use of octave band analysers which provide information on the frequency composition of the noise being generated by a noise source. The results of measurement are used to assess options for the application of engineering noise controls. 6
Competent Persons for Noise Monitoring A competent person is an individual who is trained to conduct proper noise monitoring. He should work with HCP administrator to ensure the noise monitoring is properly conducted. The tasks of a competent person include: 1. Identify work areas with excessive noise i.e. areas where persons employed are exposed or likely to be exposed to noise levels at or above 85 db(a). 2. Identify individual noise sources (e.g. equipment, machines, processes, operations and work activities) which contribute to the excessive noise in the work areas. 3. Monitor or assess the noise exposure levels of individual persons working in the work areas, which have been identified to have excessive noise. Determine whether the noise exposure levels of individual persons are excessive i.e. at or above an equivalent sound pressure level of 85 db(a) over an 8-hr period per day. 4. Conduct noise monitoring or measurements at regular intervals (at least once every three years) or whenever there is any change in equipment, machinery, processes, operations, controls or other conditions, which may result in excessive noise generation or emission. 5. Ensure that the instruments used for noise monitoring are properly and adequately calibrated. The accuracy of the instruments should be verified with an acoustic calibrator immediately before and after every measurement. In addition, the instrument used should be sent to the manufacturer or its authorised agents for servicing and maintenance at interval recommended by the manufacturer. 6. Ensure that noise measurements performed are representative of employee s normal daily exposure to noise. To obtain representative results, the following should be considered: Ensure adequate sampling of all work processes. Ensure adequate duration of sampling. Discuss with employees to have a better understanding of the work environment and processes monitored so as to obtain a more representative measurement. 7. Ensure the appropriate selection of parameters, such as weighting network, meter s response, exchange rate, criterion levels and threshold levels for accurate noise measurements. Normally an A weighting network is used to measure the average noise levels while a C weighting network is used to measure peak and impact / impulse noise. Most sound measuring instruments have two response characteristics: slow and fast. With the fast response, the device responds closely the sound level as it changes. Slow response tends to be more sluggish and gives an average of the changing sound level. Normally, the instrument is set at slow response, especially if the sound pressure fluctuates rapidly. 8. The following points should be noted during measurement: Measure at a suitable distance from the noise source. The sound measuring instrument should be held at arm length or using a remote microphone to avoid reflections from the body. Keep away from reflecting surfaces. Ensure that there are no obstacles between the noise source and the instrument. Check background noise level and make corrections if necessary. Use a wind shield to protect the microphone. 9. Prepare a Noise Monitoring Report in the manner specified in the 2 nd Schedule of the Workplace Safety and Health (Noise) Regulations, which can be found in Appendix 3. 10. Perform a noise mapping of work areas with excessive noise, including a contour of 85 db(a) around the noise source(s) on the noise map. 7
11. Present and explain the results of noise monitoring in a clear and understandable format to the management and employees. Ensure that results of the noise monitoring performed are communicated to all persons exposed to excessive noise not later than 14 days after preparation of the report. 12. Assist management in implementing a job rotation schedule for the exposed persons if engineering noise controls are not practicable. 13. Assist management in implementing a maintenance programme for equipment and machinery to minimise noise generation from friction, wear and tear, or unbalanced parts of machines. 14. Assist management in compliance with the Code of Practice (CP) 76 on the Selection, Use, Care and Maintenance of Hearing Protectors. 15. Assist management in implementing a Hearing Conservation Programme, which includes regular noise monitoring, hearing protection and health education of persons exposed to excessive noise. EVALUATION OF NOISE RISK After the noise hazards have been identified, the risk associated with the hazards should be evaluated to determine if it is acceptable or if control measures are needed. The results of the risk evaluation must be endorsed by the Employer, and he/ she must communicate all risk assessments to the employees, and monitor the implementation of the follow up actions. The risk of developing NID depends on the noise exposure level: Average noise Risk of NIHL (%) * exposure (dba) 80 1 85 8 90 25 * Number of employees who will develop NIHL in every 100 occupational noise- exposed population. (Source: Criteria for a Recommended Standard, Occupational Noise Exposure, Revised Criteria 1998; Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, USA) 8
NOISE CONTROL After the noise hazards have been identified and evaluated, the next phase of risk assessment involves the reduction of the noise risk to an acceptable level through the application of reasonably practicable controls. The risk assessment should address priorities for action, the person responsible for implementing the controls and the assessment of residual risk after the noise controls are in place to ensure that they are effective. PRINCIPLES OF CONTROL Control or reduction of noise can be carried out: at the source along the path at the receiver The best approach to control noise is to eliminate or reduce the hazard at its source. If the noise cannot be controlled at its source, attempts should be made to control it along the path, which it travels. As a last resort, the noise control problem may be approached at the receivers or exposed persons. Noise control at the source Noise control at the source is an engineering problem. Vibration control or isolation, damping or lagging of vibrating surfaces, proper balancing and maintenance of machinery can reduce noise. Mufflers or silencers can control noise generated by turbulent fluid flow. Noise control along the path The control of noise along the path of transmission involves the modification of the paths by which noise travels through the air to the workers. It can be achieved by complete or partial enclosure of the source, by placing an acoustical shield or barrier wall between the source and the receiver, or by increasing the distance between them. Sometimes, the installation of acoustical absorbing materials on ceilings or walls may result in significant reduction of noise. Noise control at the receiver Noise control at the receiver can be achieved by the use of hearing protectors, by use of personal enclosure or by application of administrative controls such as job rotation. 9
METHODS TO CONTROL NOISE HAZARDS The control of noise hazards can be accomplished through the following hierarchy of control: Safe Workplace Elimination Substitution Engineering Controls Safe Worker Administrative Controls Personal Protective Equipment SUBSTITUTION AND ENGINEERING CONTROLS Under the Workplace Safety and Health (Risk Management) Regulations, reasonably practicable steps should be taken to eliminate any foreseeable safety and health risk at in the workplace, including excessive noise from equipment and machinery. Where it is not reasonably practicable to eliminate the risk, the option of replacing noisy machines with quieter ones should be considered. Intrinsically quieter machinery is often more efficient, easier to maintain and less costly than machinery retrofitted with treatments. Engineering noise control is another measure which can be taken to minimise the risk. It involves the application of physical means to reduce the noise level at the source, along the path or in the hearing zone of the employees. Examples of noise controls include: 10
Noise control measures 1. Substitution Examples 1.1) Substitution of noisy machinery/ equipment with new machinery/ equipment designed for operation at lower noise levels. Noisy machinery/ equipment Pneumatic ejector Mechanical press Square shear Gear drive Single operation die Power press Substitute Mechanical ejector Hydraulic press Rotating shear Belt drive Step die Laser cutting Substitution of jack hammer (left photo) with automated machine (right photo) to break concrete. The noise level was reduced from 90 dba to 83 dba. 1.2) Substitution of noisy processes with less noisy ones. 2. Engineering Controls 2.1) Control noise from sources with vibrating surfaces. Noisy Processes Rolling or Forging Riveting Chipping Substitute Pressing Welding Arc or flame gouging a) Reduce the driving force of vibrating surfaces Reduce the speed Maintain dynamic balance Provide vibration isolation b.) Reduce the response of vibrating surfaces Increase damping Provide additional support Increase stiffness of material Increase mass of vibrating members Modify size to change resonance frequency c.) Reduce the sound radiation from vibrating surfaces 2.2) Modify material handling processes to ensure that impact and shock during handling and transport are minimised. Reduce area of vibrating surface Reduce overall size Use perforated panels instead of solid ones. Minimise height of fall onto hard surface. Provide wear resistant rubber or plastic coatings to absorb shocks. 11
2.3) Reduce noise produced by fluid flow. Install intake and exhaust mufflers or silencers. Reduce velocity of fluid flow. Increase cross section of streams. Reduce pressure. Reduce air turbulence. Expansion chamber (right photo) was installed at the outlet of the calibration nozzle (left photo) to reduce the noise generated by the high air jet at the nozzle. The noise level was reduced from 112 dba to 80 dba. Noise Control along the Transmission Path 2.4) Reducing noise transmitted through the air. Complete enclosure of noise sources Confine high-noise machines to insulated room and acoustically treat the area. Use of sound absorbing material on walls and ceilings in working areas to reduce sound level due to reverberation. Erect acoustic barrier between the noise source and the workers. The noise generating chamber blast pot (left photo) was completely enclosed (right photo). The noise level was reduced from 85 dba to 78 dba. 2.5) Reduce noise transmitted through solid structures. Flexible mountings Flexible section in pipe runs Flexible-shaft couplings Fabric sections in ducts Resilient flooring Noise Control at the Receiver 2.6) Enclose the workers to minimise the noise transmitted to them. Personal enclosure Some of the noise control measures described above can be implemented easily by plant personnel. Other measures may require detailed noise analysis and specialised technical knowledge to obtain the desired results. In both cases, employees, particularly those who are directly involved in the work, should be encouraged to participate in the development of the control measures to ensure that the controls are practical and will not interfere with his or her tasks. On the other hand, the noise control officer can advise on the feasibility of the measures developed. Involving the employees in decisions can help improve working relationships and make the employees more receptive to the new controls measures implemented. In addition, other potential health issues, such as ergonomics and lighting, associated with the engineering controls should be taken into consideration during the design of the controls. 12
ADMINISTRATIVE CONTROL Administrative control is any arrangement or procedure that limits the daily noise exposure of persons by control of the work or production schedule. Examples of administrative methods are: Shortening the length of time a person is exposed to excessive noise by job rotation and Scheduling machine operating times to reduce the number of persons exposed to noise Job rotation will reduce the noise exposure of some employees while increasing that of others, so care and judgement is needed. Employees will need to be rotated away from noisy jobs for a significant proportion of time to make an appreciable difference to their daily exposure. Administrative methods do not reduce the noise level and therefore should not be used as a primary means of preventing hearing loss. However, administrative control can be considered when engineering methods are not practicable. PERSONAL PROTECTION Appropriate, properly fitting and individual hearing protectors should be considered as an interim solution to reduce the sound exposure of the employees before engineering and administrative noise controls can be administered or when the controls are not yet feasible. It can also be used to provide added protection in addition to the engineering and administrative controls. MANAGEMENT RESPONSIBILITIES IN NOISE CONTROL 1. The management shall ensure that noise control measures are in place such that no employees are exposed to excessive noise. 2. Where 50 or more persons employed are exposed or likely to be exposed to excessive noise, a competent person (Noise Control Officer) should be appointed to advise the management on all proper noise control measures. 3. The management shall ensure that the individuals who advise on noise control are suitably qualified to plan noise control, whether in-house personnel or service providers. 4. The management shall allocate appropriate resources and as far as is reasonably practicable, implement the noise control plan put up by the competent person. 5. The management shall ensure that the noise control plan be reviewed at least once every three years or until such time when the noise is reduced to an acceptable level and the noise exposure hazard is eliminated. 6. The management should consider the noise emission levels during the selection and procurement of new machines since the selection of quieter machines at the initial stage can bring about cost savings in terms of the introduction of noise control measures once they are installed or used. 7. The management shall ensure that all noise control systems or devices are maintained to remain effective and to prevent their deterioration over time e.g. a machine enclosure shall be kept closed and its seals are in good condition; isolators shall be replaced as they compress with age. COMPETENT PERSON FOR NOISE CONTROL A noise control officer is an individual who is adequately trained and knowledgeable on the details of noise control to provide the management with sound advice on the proper noise control measures. He / She should work with the HCP administrator and the employees to ensure that the proposed noise control measures are implemented. The tasks of the noise control officer include 13
1. Identify all possible noise sources. 2. Evaluate specific machinery or noise source for noise control, and determine the most practical and effective methods of reducing the noise to meet the desired criteria. 3. Involve the machine operators or production people on the selection of the noise control measures which may interfere with their work; communicate with them on the proper use of the noise control devices to ensure that the controls are kept in good condition. 4. Develop a comprehensive noise control plan with recommendations on engineering noise controls where practicable. A template of the noise control plan can be found in Appendix 4. 5. Work closely with the management when putting up the noise control plan, especially in recommending priorities and setting targets for noise control. 6. Assist the management in implementing the noise control plan and evaluating the effectiveness of noise control measures. 7. Review and revise the noise control plan once every three years after the noise monitoring and when there is a significant change to the work processes or machinery. NOISE CONTROL PLAN Once it has been ascertained through the risk evaluation process that risks posed by the excessive noise present at the workplace is unacceptable, noise control measures should be proposed as part of the risk assessment process to address the noise hazards identified. The proposed control measures, the implementer and the target date of completion should be documented in the risk assessment form. From the risk assessment, an action plan for noise control can be developed in which priorities for action can be established based on the level of risks. The following should be taken into consideration when developing the noise control action plan: 1. Noise control measures for new and existing processes, machinery and equipment should be considered. 2. In the case of new processes, machinery and equipment, the noise control officer shall, where possible advise the management to: specify low noise output of the processes, machinery and equipment as a condition of purchase alongside production-related specifications; arrange the workplace layout to minimise noise exposure to the employees. 3. In the case of existing processes, machinery and equipment, the noise control officer shall advise the management to consider whether the noisy process could be carried out in another way without generating excessive noise. 4. If elimination of the noisy process or machine is not practicable, the noise control officer shall advise the management to consider replacing its noisy parts with quieter alternatives. 5. If elimination and substitution are not practicable, the use of engineering and administrative controls should be considered. 6. Hearing protectors must be provided to all persons exposed to noise hazard during the interim period of noise control implementation and in the absence of feasible engineering and administrative controls. The noise control officer shall advise the management to provide hearing protection devices and ensure their correct use by the affected employees. After the noise control action plan has been developed, it should be endorsed by the top management to ensure commitment to the implementation of the controls. There should be regular monitoring of 14
the noise control projects to ensure timely completion. After the noise control measures have been implemented, their effectiveness should be evaluated through assessing the residual risk. 15
HEARING PROTECTION The purpose of hearing protection is to ensure that the exposed persons are adequately protected from excessive noise. Employees who are exposed to excessive noise should be provided with suitable hearing protectors. The hearing protectors serve to protect the employees against excessive noise during the interim period before the noise is successfully reduced through engineering control measures, or when engineering or administrative measures are not feasible. Before hearing protectors are issued to the affected employees, the need for their use and limitations should be fully explained. TYPES OF HEARING PROTECTORS There are basically two main types of hearing protectors: Types of hearing protectors Advantages Disadvantages 1. Ear Muffs A single size can fit most employees Easily worn and taken off Generally provide better protection compared to ear plugs More durable Easily seen at a distance to assist in the monitoring of their use Not easily misplaced or lost Ear muffs consist of a pair of cushioned cups that form a seal around the ears. The muffs are designed to cover the entire ear, preventing the entry of noise. More expensive Uncomfortable to wear, especially in hot environment Difficult to use in tight spaces More inconvenient for use with other personal protective equipment May interfere with the wearing of safety or prescription glasses: wearing glasses results in breaking the seal between the ear muff and the skin, reducing hearing protection. 2. Earplugs Small Cheap Convenient to use with other personal protection equipment More comfortable in hot, humid work areas Convenient for use in confined work areas Requires more time to fit More difficult to insert and remove Require good hygiene practices May irritate the ear canal Easily misplaced More difficult to see and monitor usage Non-disposable or reusable ear plugs are made of silicone, rubber or plastic and come in various shapes and sizes as the size of the ear canal varies from person to person. 16
Disposable ear plugs are made of polyurethane foam or glass wool and are used a few times and thrown away. SELECTION OF HEARING PROTECTORS The following factors should be considered when selecting hearing protectors: 1. The noise exposure level of the employees Hearing protectors provide about 15 dba of reliable protection for majority (about 84%) of the workforce. Therefore, employees who are exposed to a noise level of above 100 dba while wearing hearing protectors can still incur substantial hearing loss over a lifetime since the protected ears would still be exposed to a noise level higher than 85 dba. Noise exposure level Choice of hearing protectors < 100 db(a) ear plugs or ear muffs > 100 db(a) ear plugs and ear muffs 2. The degree of attenuation required In selecting hearing protectors, one must know the noise exposure level and the noise reduction rating (NRR) of the hearing protectors, which is the expected level of noise reduction in the ears when they are properly worn. The higher the NRR, the higher is the attenuation for a specific ideal situation. The NRR is provided by the manufacturers and it differs from one model to another. According to NIOSH, the labelled NRRs provided by the manufacturers should be adjusted as follows: Types of hearing protectors Earmuffs Foam earplugs and custom molded earplugs All other earplugs including semiinserts Recommended Adjustment to labelled NRR Subtract 25% from the manufacturer's labelled NRR Subtract 50% from the manufacturer's labelled NRR Subtract 70% from the manufacturer's labelled NRR After the labelled NRR has been adjusted, the following approach can be used to determine the exposed noise level (ENL) for the employees: If the noise exposure levels in dba is determined through measurement using a sound level meter or noise dosimeter, the effective A-weighted ENL is: ENL = sound pressure level in dba - (adjusted NRR -7) If the noise exposure level in octave bands is known, the noise exposure level in dbc can be calculated and the ENL is: 3. Comfort & fit to the user ENL = sound pressure level in dbc - adjusted NRR Individual fitting of the hearing protectors is necessary to ensure optimum performance. Adequate protection can be readily achieved if the hearing protectors are individually fitted to each employee to achieve an acoustic seal with acceptable comfort. 17
4. Suitability for use The hearing protectors selected should be suitable for the working environment and the type of job involved. For example, ear muffs will be a preferred choice over ear plugs in unclean working conditions, where there is a risk of infection to the user while ear plugs are recommended in work areas with high temperature and humidity. 5. Need for hearing warning signals and speech intelligibility The selected hearing protectors should be able to reduce the noise level to below the PEL of 85 dba at the ear. However, employees should not be issued hearing protectors with unnecessarily high attenuation as it may bring about communication difficulties and cause isolation. Such problems caused by over protection can result in employees refusal to wear the hearing protectors. A suitable hearing protector should reduce the noise level to between 5 and 10 db(a) below the PEL. 6. Medical Conditions Before hearing protectors are issued to the employees, they should be consulted to determine if they are suffering from any medical conditions related to the ears, such as irritation of the ear canal. In which case, they should avoid the use of ear plugs. Each employee reacts individually to the use of the hearing protectors. Therefore, a successful HCP should consider and respond to the needs of each employee. Employees should be provided with a range of hearing protectors to enable them to choose the appropriate ones, which fit them comfortably. Such employees involvement in the selection of their hearing protectors will increase their acceptance and hence, encourage wearing of the hearing protectors. Management can also promote the wearing of hearing protectors at the workplace by requiring all personnel including the managers, supervisors and visitors to wear the protectors at times when in the hearing protector areas. Such practice will also demonstrate the management s commitment to hearing protection. In addition, the management can also encourage the employees to use their hearing protectors while they are involved in noisy activities outside working hours. PROPER WEARING OF HEARING PROTECTORS Improper wearing of hearing protectors can lead to diminished hearing protection. Thus, employees should be adequately trained in the correct wearing of the hearing protectors to ensure that they receive the maximum protection available. In addition, employees should be encouraged to periodically check if they need to readjust their protectors during the course of their work, in order to maintain a reliable fit. For re-usable ear plugs, pull the ear lobe backwards and upwards, then insert. This would ensure a proper fit. The disposable foam ear plugs have to be rolled before inserting into the ears. The ear cup of the ear muffs should cover the ear lobes completely. Employee receiving training on the proper wearing of hearing protectors 18
Correct method of wearing ear plugs Proper usage of ear muffs MAINTENANCE OF HEARING PROTECTORS Besides training employees on the proper use of their hearing protectors, employees should also be trained in the care of their hearing protectors to ensure that they work effectively. For personal hygiene, re-usable ear plugs must be washed frequently in warm, soapy water. Disposable ear plugs can also be washed, but should be discarded when they can no longer return to their original shape. Cleaning of ear plugs Cleaning of ear muffs Wear and tear and hardening of the ear plugs or ear muff cushions can result in cracking and loss of shape, resulting in improper fit. Hearing protectors should be checked regularly and replaced when necessary. They should be kept in a clean place when not in use. A system should be set up to check the state of the hearing protectors on a regular basis and for employees to seek repair and replacement whenever necessary. This would ensure that the hearing protectors are in good conditions at all times. 19
Dirty ear plugs Deformed ear muffs CONSISTENT USE OF HEARING PROTECTORS Areas where employees are likely to be exposed to excessive noise should be identified and clearly defined. Warning signs should be posted at all entrances to the Hearing Protector Areas to indicate the use of the hearing protectors. Regular inspections should be conducted to ensure that the employees are wearing the hearing protectors correctly at all times in these designated areas. Persons who do not wear hearing protectors should be counselled to understand that they are responsible for conserving their own hearing. IMPORTANT! Employees should be informed that the removal of hearing protectors for even a short period of time can significantly reduce their effectiveness and result in inadequate protection. If hearing protectors are worn for only 50% of the time, a protection of only about 3 db(a) is obtained. Persons should only take off their hearing protectors when they are away from loud noise. The graph below shows the effective protection (or the reduction in equivalent continuous noise level) provided by infinite-attenuation hearing protectors in relation to the percentage of the exposure time for which they are worn. This graph serves only as a guide to the amount of protection a hearing protector can provide. 20
Effective protection (dba) Example Percentage of time worn (logarithmic scale) For example, a person is exposed to an equivalent continuous noise level (Leq) of 105 db(a). From the graph, in order to reduce the Leq to 85 dba which is the Permissible Exposure Limit, hearing protectors have to be worn for as much as 99% of the total exposure time. In practice, however, hearing protectors do not provide infinite attenuation as some sound energy reaches the ear while they are worn. For further information on hearing protectors, please refer to the Code of Practice (CP) 76 on the Selection, Use, Care and Maintenance of Hearing Protectors. As it is uncomfortable to wear hearing protectors for long period of time in certain environments, the management should provide quiet rest areas where employees can take a break without wearing the hearing protectors. 21
TRAINING AND EDUCATION IMPORTANCE OF TRAINING AND EDUCATION Training and education is important because when employees understand the necessity to protect their hearing, they will be better motivated to actively participate in the programme. Besides the noise exposed employees, supervisors and managers responsible for the noisy areas and persons involved in the HCP should also be included in the training. The training should increase employees awareness of the hazards of noise and the approaches they can adopt to take care of their hearing. CONTENT OF TRAINING The HCP training should be carried out at least once every three years for persons exposed to excessive noise and within three months of job commencement for new employees. The training programme should cover the following subject areas: Relevant provisions of the Workplace Safety and Health Act, risk management and noise regulations Adverse effects of noise on hearing Purpose and benefits of HCP HCP policies Purpose of hearing protectors Advantages, disadvantages and attenuation of the various hearing protectors Instructions on the proper selection, fitting, use and maintenance of hearing protectors Importance of the consistent wearing of hearing protectors. Purpose and procedures of audiometric testing, including pre-test instructions Explanation of the audiometric results and the preventive measures Hazardous off-the-job noise exposures During the training sessions, employees should be encouraged to provide suggestions and comments on: Suitability of available hearing protectors in relation to their job Possible ways to further reduce the noise levels Ways to motivate wearing of hearing protectors Employees should be informed of the progress of the HCP implementation. In this way, they would appreciate the degree of management commitment to the programme. In addition to the training sessions, the discussion of hearing health topics can also be incorporated in regularly scheduled general safety meetings. All training should be conducted in a way the employees can be expected to understand, with special consideration on the language capability of individual employee. The training contents should be reviewed periodically to ensure they are effective in meeting the objectives. The effectiveness of the training can be determined through compliance with the proper and consistent use of the hearing protectors, noise controls and the procedures established for low noise working. 22
AUDIOMETRIC EXAMINATIONS Audiometric examination is an important part of the HCP as it determines if NIHL is prevented. As the signs and symptoms of NIHL are not apparent until a significant threshold shift has occurred, the results of audiometric examination can help to detect early stage of hearing loss. Such early detection of hearing loss will provide the opportunity for immediate measures to be taken to prevent further hearing loss. The results of the audiometric examinations can also be used to check if hearing protectors have been worn by the exposed subjects. THE WORKPLACE SAFETY AND HEALTH (MEDICAL EXAMINATIONS) REGULATIONS Under the Workplace Safety and Health (Medical Examinations) Regulations, all persons exposed to excessive noise must undergo pre-employment and annual medical examinations. These examinations include an audiometric examination. Some of the Regulations relevant to the HCP are: - Pre-employment checkup for employees exposed to excessive noise: Workers exposed to excessive noise must be medically examined by a designated factory doctor (DFD) and certified fit for work in the occupation before commencement of work. Periodic medical checkup for employees exposed to excessive noise: Annual audiometric examination must be conducted for all persons exposed to excessive noise. The audiometric examination has to be conducted by a person who has undergone an approved training course. All examinations shall be arranged by the employer at his expense. The employer has to keep a register of persons who are exposed to excessive noise. The occupier of the factory shall provide all facilities to the DFD to inspect any process or work in which a person examined by him is or is proposed to be employed. The employer and occupier shall provide the DFD with all information, which is relevant, and within their knowledge to enable him to carry out a proper medical examination. The Commissioner for Workplace Safety and Health may by certificate in writing (which he may in his discretion revoke at any time) exempt any factory or person from any provision of the Regulations either absolutely or subject to conditions as specified in the certificate. AUDIOMETRIC EXAMINATIONS RECORDS AND FORMS Under the Workplace Safety and Health (Medical Examinations) Regulations, records of audiometric examination must be kept for at least five years from the date of examination and the audiometric examination reports should be submitted to the Occupational Safety and Health Division. The following are forms designed for use in meeting the statutory requirements: Audiometric Examination Form (Enclosed in Appendix 5) To observe progression of condition 23
File the audiometric examination form chronologically. DFD should include the certificate of fitness/unfitness in the audiometric examination form Certificate of Fitness (Enclosed in Appendix 6) Certification by the DFD that the employee is fit / unfit for noise exposure at preemployment testing or upon re-exposure after being transferred out. Certificate of Suspension (Enclosed in Appendix 7) To certify that a person should not work in the noisy environment for a particular period of time. Register of persons exposed to excessive noise (Enclosed in Appendix 8) To know who are at risk of developing NIHL and should undergo regular medical examinations. The register should be kept up-to-date at all times. Summary Report (Enclosed in Appendix 9) Summarises the findings of a round of medical examinations. The Occupational Safety and Health Division requires a copy of the report to be forwarded to the Division together with the abnormal audiograms. NOTIFICATION PROCEDURE Under the Workplace Safety and Health (Incident Reporting) Regulations, persons suspected to be suffering from NIHL have to be notified to the Commissioner for Workplace Safety and Health. The employer of that employee shall submit a report to the Commissioner, not later than 10 days after receipt of the written diagnosis prepared by the registered medical practitioner diagnosing the NIHL. Similarly, any registered medical practitioner who diagnoses any employee with NIHL shall, not later than 10 days after the diagnosis, submit a report to the Commissioner. Any notification or reporting shall be made in such form and manner as set out at the website http://www.mom.gov.sg/ireport. AUDIOMETRIC EXAMINATIONS Accurate audiometric results help to ensure correct interpretation of findings and correct diagnosis. The results also help reduce employees and employer s anxiety from false positive results, and unnecessary time wastage from repeat tests. 24
Giving pre-test instructions Conducting audiometric examination To achieve an accurate test result: (a) Pre-test instruction to employees Employees should not be exposed to noise for at least 16 hours before the test. If this is not possible, employees should be instructed to wear hearing protectors all the time during the period of exposure before the test. This is to ensure that the test results reflect the employees actual hearing levels. (b) Acoustic environment The background noise level can interfere with and affect the accuracy of the test results. Therefore, testing should be conducted in an environment where the background noise level does not exceed the levels given below (e.g. inside an audiometric booth). DFDs should check the audiometric testing facilities to ensure that they meet the standard. Octave Band Centre Frequency (Hz) Sound Pressure Level (db) 250 40 500 40 1000 40 2000 47 4000 57 6000 62 8000 67 (c) Audiometer: DFDs should ensure that their audiometers are calibrated regularly. 25