Occupational Noise Surveys

85 decibels (dBA) Lex for an eight-hour period, or an equivalent noise exposure of one Pascal-squared hour (pa2h). For impact noises, a 140dBC peak sound level cannot be exceeded.

The risk of hearing loss depends on the loudness of the noise, and how long the workers are exposed to the noise. Leq is the average noise level measured by an integrating sound level meter. Lex is the Leq that has been corrected for shift lengths other than eight hours. Lex is the noise level, averaged over eight hours, which gives the same noise exposure as would the varying noise over a typical full work shift. Lex, therefore, includes both loudness and length of exposure. Another way of expressing noise exposure is by “noise dose”. Noise dose is measured in units called Pascal-squared hours, abbreviated as Pa2h. A noise exposure of 85dBA Lex is equal to 1 Pa2h.

The intensity of sound is measured in units called decibels (dB). Intensity is perceived as loudness. The notation dBA refers to decibels measured on a sound level meter using the A-weighting filter network. Once the A-weighting scale is selected, the meter will mimic the way the human ear responds to sound. Occupational noise surveys must be done with a sound level meter using the A-weighting network.

To identify significant sources of noise in the workplace and to help prioritize them for noise control measures. To determine noise exposures of workers and to identify workers who require hearing protection, hearing testing, education, and training. To determine workplace areas that should be posted as hazardous noise areas.

Area and spot measurements are a good first step, but do not incorporate information about the length of exposure. Area measurements may either overestimate or underestimate a worker’s noise exposure leading to inappropriate selection of hearing protection and inaccurate identification of workers who require annual hearing tests.

Measuring noise exposure is done with noise dose meters or integrating sound level meters. The integrating sound level meter is a hand-held instrument, while the noise dose meter is a small device worn by the worker to cover a job position that moves throughout different noise exposures in the work day (i.e. Millwright, Supervisor).

Noise measurements must be carried out in accordance with acceptable standards. Canadian Standards Association (CSA) Standard Z107.56-13, Procedures for the Measurement of Occupational Noise Exposure, provides guidance on the type of equipment to use, which workers test, and how to test. For a detailed discussion of noise measurement techniques and sampling strategies, please see the booklet, Occupational Noise Surveys, and can meet its requirements.

A written report on the results of the noise survey should contain a list of jobs that are overexposed and require hearing protection and annual hearing tests. A list of jobs whose workers need to be trained and educated about the effects of noise on hearing, and on hearing conservation techniques. Locations that need to be posted with signs warning about high noise levels, and the requirement to wear hearing protection. A statement noting that the measurements were taken under typical noise conditions (or otherwise) at the survey times. The dates of the measurements and the noise measuring equipment used should be recorded. Explanations to account for the unusual or different noise measurement levels resulting from changes in the daily work routine, if necessary.

The best method of dealing with noise in the workplace is reducing the noise at the source with engineering controls. At best, engineering controls can eliminate the need to provide hearing protection, hearing testing, and other elements of a hearing conservation program altogether. At a minimum, noise control can improve speech communication and reduce annoyance due to noise. Employers must investigate options for engineered noise control when workers are exposed to noise above the exposure limits. Investigating noise control options requires a knowledge professional such as an acoustical engineer.

• whenever workers’ noise exposures could have changed,
• when machinery is being installed or removed,
• when workload or equipment operating conditions have changed, causing significant changes in noise levels,
• when a building’s structure has changed (i.e. a wall removed or added), and
• when the length of time employees spend in noisy areas has changed.

If workers are identified as being exposed to noise based on other information, and an effective noise control and hearing conservation program is in place, employers do not have to measure the actual noise exposure of the worker.

Statistics showing the noise levels your workers are exposed to is essential in knowing how to protect their hearing today and prevent future hearing loss.