Question

The permissible time limit of 120 dB noise is .........

• A. 30 seconds
• B. 2 minutes
• C. 1 minute
• D. 30 minutes

Hint:

Remember: For every 3 dB increase in noise level above 85 dB, the permissible exposure time halves.

Answer 1

The Correct Option is A

According to occupational noise exposure standards, as noise levels increase, the permissible exposure duration decreases exponentially to prevent hearing damage. Based on the Occupational Safety and Health Administration (OSHA) and National Institute for Occupational Safety and Health (NIOSH) guidelines:
- At 85 dB: maximum exposure is 8 hours.
- For every 3 dB increase, the exposure time is halved.
Using this rule:
- At 90 dB → 4 hours
- At 100 dB → 1 hour
- At 110 dB → 15 minutes
- At 120 dB → 30 seconds
Noise levels above 120 dB can cause immediate harm and even permanent hearing loss if exposure exceeds this limit. Therefore, the correct permissible time limit for 120 dB noise is 30 seconds.