Monday Tech Talk – Noise-Induced Hearing Loss (NIHL)

Noise-Induced Hearing Loss (NIHL) remains one of the most widespread and preventable occupational health conditions in the world. Despite being entirely avoidable, it continues to affect workers across industries—particularly construction, manufacturing, engineering, and other high-noise environments. This article explores what NIHL is, how it develops, the legal requirements in South Africa, and the practical measures workers and employers must take to prevent hearing damage.

What Is Noise-Induced Hearing Loss?

NIHL is permanent hearing damage caused by exposure to excessive noise. It can occur suddenly—through an explosive sound—or gradually over years of exposure to loud machinery, tools, or environments. The damage occurs in the inner ear, where tiny hair cells translate sound into signals for the brain. Once these cells are damaged, they cannot regenerate, making NIHL irreversible.

Both occupational and recreational noise can cause hearing loss. Power tools, compressors, drills, and machinery pose risks on site, while concerts, loud music, and shooting ranges pose risks off site.

Recognising the Symptoms

Common symptoms of NIHL include:

• Difficulty hearing high-pitched sounds
• Struggling to understand speech, especially in background noise
• Persistent ringing in the ears (tinnitus)

These symptoms may appear gradually and often go unnoticed until significant damage has occurred.

Temporary vs Permanent Threshold Shifts

A threshold shift refers to a change in the softest sound a person can hear.

Temporary Threshold Shift (TTS)

• Short-term reduction in hearing
• Often caused by brief noise exposure
• Hearing typically recovers within hours or days

Permanent Threshold Shift (PTS)

• Long-term or irreversible hearing loss
• Caused by repeated or intense noise exposure
• Leads to NIHL

Repeated TTS episodes frequently progress into permanent damage.

36998d7d-933f-44ab-a4ad-cd05690…

Loud sound waves carry high energy. When they vibrate the eardrum and inner-ear structures for too long, the sensitive hair cells in the cochlea become damaged—especially at high frequencies between 3,000 and 6,000 Hz.

Hearing Aids for NIHL

While hearing aids do not restore lost hearing, they help individuals manage the effects of NIHL. Options include:

• Behind-the-Ear (BTE): Durable and suited for severe loss
• Receiver-in-Canal (RIC): Discreet with strong sound quality
• In-the-Ear (ITE) and In-the-Canal (ITC/CIC): Compact and discreet

These devices improve quality of life but do not replace prevention.

Legal Framework in South Africa

The Occupational Health and Safety Act No. 85 of 1993 requires employers to:

• Identify and control noise hazards
• Educate employees about risks
• Provide a safe working environment
• Conduct ongoing hearing tests

The Noise-Induced Hearing Loss Regulations (2003) further state:

• 85 dB(A) is the current permissible exposure level over 8 hours
• From 2025, the action level decreases to 82 dB(A)
• Peak sound exposure must never exceed 140 dB(C)

Employers must also provide SABS-approved hearing protection, display warning signs, and conduct baseline and annual audiometric testing.

Medical Surveillance and PLH

Percentage Loss of Hearing (PLH) is calculated using audiometric thresholds at frequencies from 500 Hz to 4,000 Hz. It helps determine:

• Decline in hearing over time
• Eligibility for compensation
• Whether further intervention is required

Required audiometric testing includes:

• Pre-placement baseline tests
• Annual surveillance
• Exit audiograms upon project or employment completion

Preventative Measures: The Most Effective Strategy

Risk Assessment

Use calibrated noise meters to assess frequency, intensity, and duration of exposure. Data-driven assessments guide the correct selection of controls.

Engineering Controls

Reduce noise at the source through:

• Barriers and acoustic screens
• Equipment enclosures
• Regular maintenance
• Job rotation to limit exposure duration

Administrative Controls

Implement systems that minimise worker exposure:

• Scheduling quieter work periods
• Segregating noisy zones
• Conducting toolbox talks and refresher training

Training and Awareness

Workers must understand how NIHL occurs, how to recognise early signs, and how to correctly use hearing protection.

Personal Protective Equipment (PPE)

Selecting the correct hearing protection is essential. South African standards include:

• SANS 1451 – Performance of hearing protectors
• SANS 10083 – Noise measurement and assessment

Common PPE options include:

• Foam earplugs (single-use)
• Pre-moulded plugs (reusable)
• Earmuffs (effective for intermittent noise)
• Electronic earmuffs (allow communication)
• Dual protection (plugs + muffs) for exposures above 100 dB(A)

Fit Testing: Ensuring PPE Actually Works

Proper fit is critical. Fit-testing involves:

• Training workers on how to insert or wear PPE correctly
• Measuring the real attenuation achieved
• Comparing results against noise exposure levels
• Re-testing and retraining when protection is inadequate
• Recording results for compliance

A poorly fitted earplug offers little to no protection.

Becoming a Qualified Audiometrist

To conduct occupational audiometric testing in South Africa, technicians must:

• Complete required self-study hours
• Attend a practical workshop
• Compile a portfolio of evidence
• Register with SASOHN
• Complete refresher training every two years

With the noise action level dropping to 82 dB(A) in 2025, early intervention is no longer optional—it is a compliance requirement. NIHL cannot be reversed, but it can be completely prevented through responsible management, correct PPE, engineering controls, and a proactive safety culture.

Protect your hearing now. The damage you prevent today safeguards your quality of life tomorrow.