Okanagan Audio Lab

Hearing Tests

Noise Survey

Q: What are the regulated limits set by the WCB for noise exposure? A: 85 decibels (dBA) Lex for an eight-hour period, or an equivalent noise exposure of one Pascal-squared hour (pa2h). For impact noises, a 135 dBA peak sound level cannot be exceeded. Q: What are Lex and Pa2h? A: 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 does". Noise dose is measured in units called Pascal-squared hours, abbreviated as Pa2h. A noise exposure of 85dBA Lex is equal to 1 Pa2h. Q: What's the difference between dB and dBA? A: 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. Q: What is the purpose of carrying out noise measurements? A: 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. Q: Why can't I just take area or spot measurements and say I have done a survey? A: 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. Q: What equipment do I need to give me accurate results? A: 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). Q: What training is required to perform noise surveys? A: Noise measurements must be carried out in accordance with acceptable standards. Canadian Standards Association (CSA) Standard Z107.56-M86, 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. Q: What is done with the information once noise measurements are done? A: 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. Q: What is Engineered Noise Control? A: 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. Q: When should noise measurements be redone? A: Measurements must be redone whenever workers' noise exposures could have changed when: machinery is being installed or removed; workload or equipment operating conditions have changed, causing significant changes in noise levels; a building's structure has changed (i.e. a wall removed or added). The length of time employees spend in noisy areas has changed. Q: I have heard that I can be exempted from noise measurements, is that true? A: 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.

Explanation of Categories

A - Abnormal: In this category the test showed some hearing loss in the lower tones. We are not qualified to say what may have caused the hearing loss, as hearing loss in the low tones is not generally noise related. At the time of counseling we would give the employee a copy of their test results and recommend they see their general doctor. Also we stress the importance of proper fitting hearing protection on and off the job. EW - Early Warning: In this category the test showed some hearing loss in the higher tones. Often the hearing test will pick out the first sign of noise-induced hearing loss even though the individual may not have noticed any problems yet. At the time of counseling we would stress how important it is to wear proper fitting hearing protection on and off the job. N - Normal: In this category the test showed good hearing in all tones. At the time of counseling we would stress how important it is to wear proper fitting hearing protection on and off the job. AC - Abnormal Change: In this category the test showed hearing that has gotten worse rapidly. The large amount of change is not due to noise exposure; some other medical condition is present at the time of the test. We are not qualified to determine what this condition may be. At the time of counseling the employee we would give them the test results of this year and previous year and recommend they see their general doctor. Also we stress the importance of proper fitting hearing protection on and off the job. EWC - Early Warning Change: In this category the test showed there has been hearing loss in the higher tones due to noise exposure. The high tones are the tones sensitive to noise exposure and this kind of change usually indicates that the employee been exposed to too much noise since the last test. This exposure may happen because their hearing protection is not blocking the noise effectively because it does not fit or is in poor condition. Or the employee may not be wearing their hearing protection all the time or not at all. Again we stress the importance of proper fitting hearing protection on and off the job. NC - Normal Change: In this category the test showed no significant change from the previous hearing test. At the time of counseling we would stress how important it is to wear proper fitting hearing protection on and off the job.

OKANAGAN AUDIO LAB LTD.
6048 Star Road, Vernon, BC V1B 3P4 Canada
Tel: (250) 542-1686, Toll Free: 1-800-663-2884
Fax: (250) 542-7318