Noise Measurement and Control Flashcards

An occupational hearing conservationist is tasked with measuring the noise exposure of a maintenance worker who moves between various high-noise areas throughout an 8-hour shift. Which instrument is MOST appropriate for accurately determining this worker's full-shift Time-Weighted Average (TWA) exposure?

Answer: A noise dosimeter

A noise dosimeter is a small, body-worn device that measures and stores sound levels over a period of time, such as a full work shift. It is the ideal instrument for assessing the personal noise exposure of mobile workers, as it captures the varying noise levels they encounter in different locations. [2, 10] A sound level meter measures noise at a specific location at a specific time, while an octave band analyzer provides frequency information, and a calibrator is used to verify instrument accuracy.

According to the OSHA Noise Standard (29 CFR 1910.95), when an employee's noise exposure equals or exceeds an 8-hour time-weighted average (TWA) of 85 dBA, the employer is required to:

Answer: implement a hearing conservation program.

OSHA's standard establishes an Action Level (AL) of 85 dBA as an 8-hour TWA. [5, 17] When this level is met or exceeded, the employer must implement a comprehensive hearing conservation program, which includes noise monitoring, audiometric testing, training, and making hearing protection available. [15] Engineering or administrative controls are required when the Permissible Exposure Limit (PEL) of 90 dBA is exceeded.

Which of the following represents the most effective type of noise control according to the established hierarchy of controls?

Answer: Replacing a noisy piece of equipment with a quieter model.

The hierarchy of controls ranks methods of controlling hazards from most to least effective. Elimination and Substitution are at the top. Replacing a noisy machine with a quieter one is an example of substitution, which physically removes the hazard. [9] Engineering controls (enclosures), administrative controls (job rotation), and personal protective equipment (earplugs) are progressively less effective because they rely on additional actions or worker behavior to be successful. [3, 8]

A sound level meter's A-weighting network is designed to be most useful for hearing conservation purposes because it:

Answer: approximates the frequency response of the human ear to moderate sound levels.

The A-weighting scale filters sound to mimic how the human ear perceives loudness at different frequencies, being less sensitive to very low and very high frequencies. [18, 27] This makes it the best predictor of the potential for noise to cause hearing damage and is the standard weighting used for occupational noise exposure measurements, such as the OSHA Action Level and PEL. [24]

A manufacturing facility has a work area with a consistent noise level of 95 dBA. According to the OSHA standard, which uses a 5-dB exchange rate, what is the maximum permissible exposure time for a worker in this area during a single day?

Answer: 4 hours

The OSHA Permissible Exposure Limit (PEL) is 90 dBA for an 8-hour TWA. The standard uses a 5-dB exchange rate, meaning that for every 5 dB increase in noise, the permissible exposure time is halved. [1, 5] Since 95 dBA is 5 dB above the 90 dBA PEL, the allowed time is cut in half from 8 hours to 4 hours. [17]

Which of the following actions is an example of an administrative control for reducing noise exposure?

Answer: Changing work schedules to limit the amount of time any single employee spends in a high-noise environment.

Administrative controls involve changes to work practices or procedures to reduce exposure. Limiting the time an employee spends in a noisy area through job rotation or altered schedules is a classic example of an administrative control. [8, 9] Building a barrier is an engineering control, providing hearing protectors is PPE, and a 'Buy Quiet' policy is a form of substitution or elimination.