Hearing Protection and Noise Reduction in the Workplace

Hearing Protection

1. Noise

Noise is defined as unwanted or unpleasant sound.

1.1. Basic Principles of Noise

Sound requires a medium to propagate and cannot travel in a vacuum. The frequency of a sound wave determines its pitch, with fewer cycles per second perceived as a lower pitch (deep sound) and more cycles per second perceived as a higher pitch (acute sound). Sound pressure intensity is measured in bels, but more commonly in decibels (dB), which are a logarithmic unit. Frequency is measured in hertz (Hz). The upper limit of normal human conversation is around 2,000 Hz.

1.2. Characteristics of Noise

Noise analysis focuses on filtering harmful sound frequencies and intensities.

1.3. Addition and Subtraction of Noise

Sound pressures are not added arithmetically, but logarithmically. For example, 80 dB + 80 dB = 83 dB.

1.4. Rating Scales

The human ear has a natural self-protection mechanism to mitigate damage from excessive noise. Noise levels adjusted to account for the ear's response are measured in dBA, dBB, etc., which are weighted decibel scales.

2. Risks to Hearing

• Electromechanical: Engine noise poses a hearing risk.
• Plate: Chemical and mechanical hazards affect hearing.
• Painting: Noise from turbines and chemical contaminants from solvents are hazards.
• Warehouse: No identified risks to hearing.

3. Conditions to Fulfill

Consider market size and specific applications.

3.1. Types and Characteristics of Hearing Protection

• Earmuffs: Cover the entire ear, providing excellent attenuation, but may not be compatible with other PPE like goggles.
• Formed Earplugs: Shaped and inserted into the ear canal, easy to remove, and generally hypoallergenic.
• Reusable Earplugs: Easily adaptable.

3.2. Legislation and CE Marking

All Category 2 PPE requires CE marking.

3.3. Interpretation of Marking

• SNR (Single Number Rating): Simplified noise reduction value.
• HML (High, Medium, Low): Attenuation at high, medium, and low frequencies.
• Frequency: The frequency at which studies are conducted.
• Average Attenuation: The average attenuation in dBA offered by the protector at a specific frequency.
• Standard Deviation: The potential variation in attenuation values.
• Protection Conferred: The protection provided in the most unfavorable conditions.

4. Choosing the Right PPE

Consider the following factors:

4.1. Daily Equivalent Level

The maximum continuous noise level that should not be exceeded. This is set at 90 dBA; hearing protection is required above 85 dBA.

4.2. Noise Impact

Variations in sound pressure that are difficult to measure. Even very short bursts of sound (e.g., 0.01 seconds) can be harmful if repeated or intense enough.