CHST Noise Exposure and Hearing Conservation Programs — Questions and Answers
Question 1: Under OSHA 29 CFR 1926.52, what is the permissible exposure limit (PEL) for occupational noise averaged over an 8-hour workday?
- 85 dBA TWA
- 90 dBA TWA (Correct answer)
- 95 dBA TWA
- 100 dBA TWA
Correct answer: 90 dBA TWA
OSHA's construction noise PEL is 90 dBA as an 8-hour time-weighted average (TWA). The action level triggering a hearing conservation program is 85 dBA TWA. Exposures above 90 dBA require engineering/administrative controls and/or hearing protection.
Question 2: A concrete saw operates at 105 dBA. Using OSHA's 5 dB exchange rate, what is the maximum daily exposure duration allowed at this level?
- 1 hour (Correct answer)
- 2 hours
- 4 hours
- 30 minutes
Correct answer: 1 hour
OSHA's 5 dB time-intensity exchange rate means permissible time halves for every 5 dB increase above 90 dBA. At 90 dBA = 8 hrs; 95 dBA = 4 hrs; 100 dBA = 2 hrs; 105 dBA = 1 hr. Workers on this saw are limited to 1 hour per shift without additional controls.
Question 3: Which instrument is used to measure a worker's personal noise dose over the course of a full work shift?
- Sound level meter (SLM)
- Noise dosimeter (Correct answer)
- Octave band analyzer
- Vibration meter
Correct answer: Noise dosimeter
A noise dosimeter is worn by the worker and integrates variable noise exposures over the entire shift to calculate a percent dose or TWA. A sound level meter gives instantaneous readings at a fixed point. An octave band analyzer characterizes frequency content for engineering control design. A vibration meter measures vibration, not sound.
Question 4: An audiometric baseline test reveals that a worker has a 10 dB Standard Threshold Shift (STS) in the 2000–4000 Hz range after 6 months on-site. What is the safety technician's FIRST required action?
- Immediately remove the worker from all noisy operations
- Notify the worker in writing within 21 days and refit hearing protection to achieve greater attenuation (Correct answer)
- Repeat the audiogram in 90 days before taking any action
- Record the STS on the OSHA 300 log and take no further action
Correct answer: Notify the worker in writing within 21 days and refit hearing protection to achieve greater attenuation
OSHA 29 CFR 1910.95 (applied to construction via OSHA guidance) requires that workers be notified in writing within 21 days of an STS determination, and that hearing protection be refitted or upgraded. Removal from noise is not mandated. The STS may or may not be recordable depending on whether it is work-related and permanent.
Question 5: What is the primary purpose of the 'noise reduction rating' (NRR) labeled on hearing protection devices?
- To indicate the device's frequency cutoff for low-frequency noise
- To allow employers to estimate the degree of noise attenuation in the field (Correct answer)
- To certify the device for use in confined space noise environments only
- To specify the maximum continuous exposure duration for the device
Correct answer: To allow employers to estimate the degree of noise attenuation in the field
The NRR is an EPA-standardized laboratory rating used to estimate field attenuation. OSHA instructs employers to derate the NRR by 50% (for earmuffs) or up to 70% (for formable earplugs) to account for real-world fit variability, giving a realistic estimate of protected exposure.
Question 6: Which engineering control is most effective for reducing jackhammer noise at the source on a construction site?
- Surrounding the operator with portable noise barriers
- Requiring the operator to wear double hearing protection
- Replacing the pneumatic jackhammer with an electric rotary hammer that has a lower sound power level (Correct answer)
- Scheduling jackhammer work during morning hours when fewer workers are nearby
Correct answer: Replacing the pneumatic jackhammer with an electric rotary hammer that has a lower sound power level
Substituting a quieter tool (electric rotary hammer vs. pneumatic jackhammer) is an engineering control that reduces noise at the source — the highest level of the hierarchy. Portable barriers reduce noise for bystanders but not the operator. Double hearing protection is PPE. Scheduling is an administrative control — it reduces others' exposure but not the operator's.
CHST Noise Exposure and Hearing Conservation Programs
Under OSHA 29 CFR 1926.52, what is the permissible exposure limit (PEL) for occupational noise averaged over an 8-hour workday?