CAOHC Noise Measurement and Control 2 — Questions and Answers
Question 1: What instrument is used to measure a worker personal noise exposure over a full work shift?
- A noise dosimeter (Correct answer)
- A sound level meter
- An octave band analyzer
- An audiometer
Correct answer: A noise dosimeter
A noise dosimeter is a body-worn instrument that continuously measures and integrates sound levels to calculate cumulative noise dose.
Noise dosimeters are clipped to the worker with a microphone on the shoulder. They must be set to OSHA parameters: 90 dBA criterion level, 5 dB exchange rate, and 80 dBA threshold.
Question 2: What is the A-weighting network on a sound level meter designed to approximate?
- The frequency response of the human ear at moderate sound levels (Correct answer)
- The maximum output of industrial machinery
- The resonant frequency of the audiometric test booth
- The noise reduction provided by hearing protectors
Correct answer: The frequency response of the human ear at moderate sound levels
A-weighting adjusts sensitivity across frequencies to approximate how the human ear perceives loudness.
A-weighting attenuates low frequencies and very high frequencies while leaving mid-frequencies relatively unchanged, making A-weighted measurements correlate well with perceived loudness and hearing damage risk.
Question 3: What is the hierarchy of noise controls from most to least effective?
- Elimination, substitution, engineering controls, administrative controls, PPE (Correct answer)
- PPE, administrative controls, engineering controls, substitution, elimination
- Engineering controls only
- Administrative controls, PPE, and engineering controls equally
Correct answer: Elimination, substitution, engineering controls, administrative controls, PPE
The hierarchy ranks methods from most effective (elimination) to least effective (PPE).
OSHA requires feasible engineering and administrative controls before relying on hearing protectors when the PEL is exceeded.
Question 4: During a noise survey, what is the slow response setting on a sound level meter used for?
- To average fluctuations and provide a more stable reading (Correct answer)
- To detect very brief impulse noise peaks
- To measure noise levels below 40 dBA
- To calibrate the meter
Correct answer: To average fluctuations and provide a more stable reading
Slow response uses a 1-second time constant to average rapid fluctuations.
OSHA specifies slow response for TWA measurements. Fast response (125 ms) follows rapid fluctuations more closely. Peak detection is used for impulse noise.
Question 5: What is an octave band analysis used for in a hearing conservation program?
- To identify frequency content of workplace noise for selecting controls and protectors (Correct answer)
- To measure the total A-weighted sound level for OSHA compliance
- To calculate the standard threshold shift
- To calibrate audiometers
Correct answer: To identify frequency content of workplace noise for selecting controls and protectors
Octave band analysis breaks the noise spectrum into frequency bands for targeted engineering controls and protector selection.
Octave band analysis provides spectral information essential for designing engineering controls and selecting hearing protectors with adequate attenuation at dominant frequencies.
Question 6: Before taking noise measurements, what must be done to ensure accuracy?
- Calibrate using an acoustic calibrator at the beginning and end of measurements (Correct answer)
- Simply replace the batteries
- Hold the meter at arm length and verify the display
- Compare readings to a nearby dosimeter
Correct answer: Calibrate using an acoustic calibrator at the beginning and end of measurements
Sound level meters must be field-calibrated before and after each measurement session using an acoustic calibrator.
Field calibration uses a portable calibrator producing a known SPL. Pre/post calibration readings should agree within 1 dB. Annual laboratory calibration is also required.
CAOHC Noise Measurement and Control 2
What instrument is used to measure a worker personal noise exposure over a full work shift?