Page 40 - OHS, September 2022

HEARING PROTECTION
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Advancements in technology have transformed personal noise dosimeters from a bulky cabled unit to today’s miniaturized instruments worn in the hearing zone as defined by OSHA. Measured parameters include dose, time-weighted average (TWA) based on the dose and more (e.g., PEAK, Lavg). Dosimeters can take separate measurements (studies) for different job tasks and/or work shifts. The newest models can store individual noise sessions or studies to enable analysis and comparison/contrast among occupations. Manufacturers offer dosimeters with different features.
An important feature in today’s world is the ability to monitor noise measurement from a mobile device via an app or computer software. Downloaded data provides the whole story of a specific study and identifies noise sources contributing to overall exposure. In addition, good observations by the OEHS professional, such as description of the tasks performed during the shift, are required to support results.
Selecting the best noise dosimeter depends on specific needs and the desire for features that facilitate accurate measurement, including:
■ Reliability of the battery and microphone
■ Ease of use
■ Automatic calibration and clear access to calibration status
■ Flexibility and simplicity in setting parameters
■ Easy access to and readability of data (important for sites
with limited lighting)
■ Remote monitoring capability
Remote monitoring is especially important when performing
a survey during a midnight shift, in low lighting or for occupations where it is difficult to contact the worker during dosimetry (e.g., crane operators). With remote monitoring, the OEHS professional can easily determine if the unit is working properly.
The Good, Bad & Ugly
Let’s drill down into the good, the bad and the ugly of noise surveys. The chief objective is to record data so that it can be used to achieve the ultimate goal of protecting workers’ hearing. Based on experience with hundreds of noise surveys, the following considerations stand out as being crucial to a successful occupational noise survey.
Research applicable standards and develop a plan. Some research is needed before looking at the data. Investigate applicable occupational noise exposure regulations and guidelines. The regulations used depend on the type of industry, country, region or state and length of work shift. It is important to know what occupations will be monitored and when the noise dosimetry should be performed. Communicate this plan to the company’s management to facilitate understanding.
Set a noise dosimeter to the correct criteria/parameters.
This includes the exchange rate, frequency weighting, response, criterion level and threshold. Many instruments now offer presets to help the user. Always double-check presets (or your own customized settings), especially if you need to make changes depending on the regulation you are following.
Pre- and post-calibrate the dosimeter. In industrial hygiene
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while performing his/her duties during a shiftft.
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Performing noise surveys can be challenging for OEHS professionals, particularly if performed infrequently.
air sampling, you pre- and post-calibrate the air sampling pump and use the average to calculate the volume of the sample. For noise, even though you don’t need to calculate air volume, you must always calibrate the instrument before and after the survey. This ensures the system’s algorithm calculates dose and TWA is accurate within set parameters. Remember that survey results may be used during litigation. If pre- and post-calibration records are not shown, the data will not be acceptable.
Place the dosimeter in the employee’s hearing zone. OSHA defines the worker’s hearing zone as the “two-foot diameter sphere around the head.”6 At times, the noise source may be coming from one area of the workplace or task. It is important to identify which area and its physical relationship to the employee’s work position. This information can help determine dosimeter placement in the worker’s hearing zone.
Use the dosimeter’s windscreen. The windscreen is an important component of both the noise dosimeter and the SLM. It minimizes interferences and/or background noises that may affect the actual noise exposure of the employee or area. It also protects the most sensitive and important part of the instrument— the microphone—from harsh conditions (i.e., abrasive blasting).
Never forget the human factor. Explaining to employees the purpose of the noise dosimeter and what to expect is key to
36 Occupational Health & Safety | SEPTEMBER 2022 www.ohsonline.com