Noise and Vibration Control

9.1 Health Effects of Noise and Vibration

Noise and vibration are common physical hazards in many industries, such as construction, manufacturing, and transportation. Prolonged exposure to excessive noise can lead to hearing loss, while vibration can cause musculoskeletal disorders and circulatory problems.

Noise-Induced Hearing Loss (NIHL):

• Cumulative Effect: Exposure to loud noises over time can damage the hair cells in the inner ear, leading to permanent hearing loss.
• Threshold: The risk of hearing loss increases when workers are exposed to sound levels above 85 decibels (dB) over an eight-hour workday.
• Symptoms: Ringing in the ears (tinnitus), difficulty hearing conversations, and the gradual loss of hearing ability.

Hand-Arm Vibration Syndrome (HAVS):

• Causes: Caused by exposure to vibration from handheld tools, such as power drills, grinders, and chainsaws.
• Symptoms: Tingling, numbness, and pain in the hands and arms, reduced grip strength, and in severe cases, loss of finger sensitivity.

Whole-Body Vibration (WBV):

• Causes: Caused by prolonged exposure to vibration while sitting or standing on vibrating machinery (e.g., heavy equipment operators).
• Symptoms: Back pain, circulatory problems, and discomfort in the spine and joints.

Table 9.1: Common Sources of Noise and Vibration

9.2 Monitoring and Measuring Noise and Vibration

Accurate measurement and monitoring are essential to assess worker exposure to noise and vibration and to implement appropriate control measures.

Noise Monitoring:

• Sound Level Meter: Measures sound pressure levels in decibels (dB) at specific locations within a workplace.
• Dosimeter: A personal device worn by workers to measure their cumulative noise exposure over the course of a workday. It provides a time-weighted average (TWA) of noise exposure.
• Octave Band Analyzer: Measures noise at different frequency bands, helping to identify specific sources of harmful noise.

Vibration Monitoring:

• Accelerometers: Devices that measure the intensity and frequency of vibration exposure. These are often attached to tools or equipment to assess vibration levels.
• Vibration Dosimeters: Worn by workers to assess personal exposure to vibration, particularly hand-arm or whole-body vibration.

Table 9.2: Noise and Vibration Monitoring Devices

9.3 Noise Control Strategies and Hearing Conservation Programs

To prevent noise-induced hearing loss (NIHL), workplaces must implement noise control strategies and establish a hearing conservation program.

Noise Control Strategies:

1. Elimination or Substitution: Whenever possible, eliminate noisy processes or substitute them with quieter alternatives.
2. Engineering Controls: Modify equipment, processes, or the workplace layout to reduce noise at the source.
   • Soundproofing: Install soundproof barriers or walls to contain noise.
   • Machine Enclosures: Enclose noisy machinery to prevent sound from spreading.
   • Damping: Apply damping materials to reduce vibration and noise from machines.
3. Administrative Controls: Reduce workers’ exposure to noise by rotating tasks or limiting time spent in noisy areas.
4. Personal Protective Equipment (PPE): Provide ear protection, such as earplugs or earmuffs, when noise levels exceed safe limits (85 dB or higher).

Hearing Conservation Program Components:

• Noise Monitoring: Regular monitoring of workplace noise levels to ensure compliance with permissible exposure limits.
• Audiometric Testing: Periodic hearing tests to detect early signs of hearing loss among workers.
• Training and Education: Teach workers about the risks of noise exposure and the proper use of hearing protection.
• Recordkeeping: Maintain records of noise monitoring results and audiometric tests for future reference.

Table 9.3: Noise Control Hierarchy

9.4 Vibration Control and Ergonomic Interventions

Controlling vibration exposure involves both engineering controls and ergonomic interventions. These strategies are aimed at reducing the amount of vibration transmitted to workers, particularly through handheld tools or machinery.

Vibration Control Measures:

1. Tool Design: Use tools with anti-vibration features or ergonomic designs that reduce vibration transmission to the hands and arms.
2. Damping Systems: Install damping systems in machines or vehicles to reduce vibration.
3. Vibration Isolation: Use vibration isolation pads or mounts under machines to minimize vibration transfer to floors and workers.
4. Maintenance: Regularly maintain and inspect tools and equipment to ensure they are operating smoothly, as worn-out equipment can generate more vibration.

Ergonomic Interventions:

• Workstation Design: Redesign workstations to minimize awkward postures and improve comfort when using vibrating tools.
• Work Rotation: Rotate tasks among workers to reduce prolonged exposure to vibrating equipment.
• Work Practices: Encourage workers to take regular breaks and minimize grip force when using vibrating tools to reduce the risk of HAVS.

PPE for Vibration:

• Anti-Vibration Gloves: These gloves are designed to reduce the transmission of vibration to the hands and can help prevent HAVS.

Table 9.4: Vibration Control Measures

Practical Applications: Noise and Vibration Control in a Construction Site

Scenario: A construction site experiences high levels of noise and vibration from heavy equipment, power tools, and machinery. Workers have reported discomfort and hearing problems, and the site is out of compliance with noise regulations.

Steps Taken:

1. Noise Monitoring: Sound level meters and dosimeters are used to assess noise levels across the site, identifying areas where noise exceeds 85 dB.
2. Engineering Controls: Noise barriers are installed around the loudest machinery, and vibration isolation pads are placed under heavy equipment to reduce vibration.
3. Personal Protective Equipment: Workers are provided with high-quality earplugs and anti-vibration gloves.
4. Task Rotation: Workers are rotated between tasks to minimize their exposure to both noise and vibration.
5. Training: Workers receive training on the risks of prolonged noise and vibration exposure and the correct use of PPE.

Outcome: Noise levels on the site are reduced, workers experience fewer health complaints, and compliance with noise and vibration standards is achieved.

Review Questions:

1. What are the health effects of prolonged exposure to excessive noise and vibration?
2. Describe two methods for monitoring noise and two methods for monitoring vibration in the workplace.
3. What are the key components of a hearing conservation program?
4. Explain how engineering controls can be used to reduce both noise and vibration in the workplace.

Further Reading:

• Hearing Conservation Programs by NIOSH
• Vibration Exposure and Control in the Workplace by ACGIH
• OSHA’s Noise and Vibration Exposure Standards

This chapter covers the health risks associated with noise and vibration exposure, including noise-induced hearing loss and hand-arm vibration syndrome. It also explains how to measure, monitor, and control these hazards using engineering controls, PPE, and administrative strategies to protect workers from long-term harm.