How to Control Noise and Vibration in Manufacturing | Wellbeing

According to National Technical Regulation QCVN 24:2016/BYT on Noise - Permissible Exposure Levels in the Workplace, issued by the Ministry of Health (MoH), the maximum permissible noise level for an 8-hour shift is 85 dB(A). Meanwhile, QCVN 27:2016/BYT stipulates that whole-body vibration must not exceed 0.54 m/s² along the z-axis and 0.38 m/s² along the x and y-axes.

1. Definition and Sources of Noise and Vibration in Manufacturing

1.1. Basic Concepts

• Noise is defined as a collection of unwanted sounds with varying intensities and frequencies that cause discomfort to the listener. Sound intensity is measured in decibels (dB), with the human ear capable of hearing frequencies between 20 and 20,000 Hz. In manufacturing, noise typically emanates from machinery such as wood saws, concrete drills, and generators, with intensities potentially reaching 140-160 dB.

• Vibration refers to mechanical oscillations from engines and tools, measured by vibration velocity (cm/s), frequency (Hz), amplitude, and acceleration. Common sources include rock drills, riveting hammers, screening machines, and compactors, often occurring simultaneously with machinery-induced noise.

1.2. Common Sources in the Work Environment

Noise and vibration frequently co-occur in heavy industries such as mining, construction, mechanical engineering, and textiles. Noise measurement utilizes sound level meters according to TCVN 6963:2001 (on vibration and shock), while vibration is measured using accelerometers to determine levels along the x, y, and z-axes. Periodic monitoring facilitates the early detection of sources exceeding permissible limits. For large-scale plants, implementing online monitoring systems to capture real-time data is highly recommended.

2. Health Impacts of Noise and Vibration on Workers

Exposure to noise and vibration causes numerous acute and chronic health issues.

For noise, the impact depends on intensity, duration, and frequency. Exposure to extreme noise (140-160 dB) can cause immediate aural damage, whereas prolonged exposure to lower levels leads to a temporary threshold shift (auditory fatigue) or permanent Noise-Induced Hearing Loss (NIHL) / occupational deafness. Early signs include difficulty understanding speech in noisy environments, tinnitus (ringing in the ears), and needing to stand close to the speaker. MoH statistics from 2022 revealed that 73.2% of occupational disease cases were noise-induced hearing loss—a sharp increase from previous years, with over 3,800 cases detected in 2017 alone. Noise also triggers anxiety, insomnia, stomach ulcers, palpitations, stress, cardiovascular disorders, and an increased risk of accidents due to loss of balance.

The progression of noise-induced diseases includes:

• Initial Stage: Workers experience headaches, dizziness, fatigue, tinnitus, and mild hearing loss.

• Latent Stage: This period lasts 5–15 years, depending on aural resistance, exposure time, and noise frequency. Specifically, working in environments above 105 dB(A) leads to ear damage after 5 years, while exposure to 100–105 dB(A) takes about 10 years.

• Occupational Deafness: At this irreversible stage, workers suffer from severe tinnitus and cannot hear even loud speech.

Individuals suffering from severe noise-induced hearing loss also face neurological and cardiovascular impacts, including arrhythmias and arteriosclerosis, leading to severe fatigue.

Regarding vibration, low frequencies (<20 Hz) can cause motion sickness and spinal damage (Whole-Body Vibration - WBV). High frequencies (20-1000 Hz) lead to Hand-Arm Vibration Syndrome (HAVS), characterized by vasomotor disorders and damage to tendons, muscles, joints, nerves, and bones.

According to the WHO, occupational diseases claim nearly 2 million lives annually, with noise and vibration being major contributors in developing nations like Vietnam.

3. Legal Regulations on Noise and Vibration Control in Vietnam

3.1. Relevant National Technical Regulations

• QCVN 24:2016/BYT dictates that continuous noise must not exceed 85 dB(A) over 8 hours. The permissible level increases by 5 dB(A) when the exposure time is halved (e.g., 90 dB(A) for 4 hours, up to a maximum of 115 dB(A) for less than 15 minutes). The absolute maximum peak cannot exceed 115 dB(A), and the remaining shift time must be kept below 80 dB(A). Recommended levels are ≤55 dB(A) for mental work and ≤85 dB(A) for factory floors.

• QCVN 27:2016/BYT governs permissible vibration limits: whole-body vibration acceleration must be ≤0.54 m/s² (z-axis) and ≤0.38 m/s² (x, y-axes). Hand-arm vibration limits vary by frequency to prevent occupational vibration syndromes.

3.2. Legal Liabilities and Penalties

The 2015 Law on Occupational Safety and Health (OSH Law) (Article 16) mandates employers to assess and control hazardous factors, provide PPE, and organize periodic occupational environmental monitoring. Pursuant to Decree 12/2022/ND-CP, violations can result in fines ranging from 80 to 100 million VND if noise levels exceed permissible limits by 25-30 dB(A).

4. Noise Control Measures in Manufacturing

Noise control must be integrated from the design phase to daily operations using the Hierarchy of Controls:

• Engineering Controls (At the Source): Replace noisy processes with quieter ones (e.g., pressing instead of striking). Design machinery with vibration-absorbing pads, perform regular maintenance (tightening bolts, lubricating), and substitute materials (using high-friction rubber to eliminate noise).

• Isolation Controls (Along the Path): Isolate the source by building acoustic walls, planting green belts around the factory, digging sound-insulating trenches (6-10 cm wide), or using deep-set sand/rubber flooring. Install sound-absorbing components like acoustic enclosures and machine silencers.

• Personal Protective Equipment (PPE): Utilize earplugs (reducing noise by 10-29 dB depending on frequency) and earmuffs for noise >120 dB, ensuring full coverage of the ear and cranial bones. Select PPE with an appropriate Noise Reduction Rating (NRR).

• Administrative Controls: Reduce exposure time through rational work schedules, job rotation, and providing quiet break areas. Conduct annual acoustic monitoring and periodic OSH training.

5. Vibration Control Measures in Manufacturing

Vibration control follows a similar hierarchy:

• At the Source: Design machines with a balanced center of gravity, utilize vibration-dampening motors, and replace high-vibration hand tools with automated alternatives. Conduct vibration analysis to predict machinery failure.

• Along the Path: Isolate propagation by installing elastic dampening pads under machines, utilizing anti-vibration foundations, and excavating isolation trenches.

• Personal Protection & Administrative: Equip workers with elastic-padded anti-vibration gloves, anti-vibration boots, and appropriate clothing for whole-body vibration. Reduce exposure time, particularly for high-vibration equipment like jackhammers, air compressors, and hand compactors (especially in cold weather).

6. Employer Responsibilities in Noise and Vibration Control

Pursuant to Article 16 of the 2015 OSH Law and QCVN 18:2021/BXD, employers hold strict responsibilities:

• Conduct comprehensive risk assessments and establish an occupational environmental monitoring plan.

• Prioritize the procurement of low-noise and low-vibration machinery.

• Provide standard-compliant PPE (earplugs, earmuffs, anti-vibration gloves) entirely free of charge.

• Organize logical work schedules to reduce exposure and implement on-site medical services.

• Conduct periodic health check-ups (including audiometry and vibration tests) per MoH guidelines to detect occupational diseases early.

• Refrain from assigning individuals with cardiovascular diseases or neurasthenia to high noise/vibration areas.

• If limits are exceeded, immediate corrective action must be taken and reported to the labor authority.