Page 38 - OHS, Nov/Dec 2023

NOISE MONITORING Methods for Evaluating Noise Exposures Understanding noise exposure evaluations, from basic area evaluations to the intricacies of equipment precision and the role of smartphone apps in noise measurements. BY GREG BOOTHE, PH.D., CIH, CSP Noise exposures and standard threshold shifts have been present in general industry and construction sites since the Occupational Safety and Health Administration (OSHA) was founded. Although safety professionals will likely deal with noise hazards at least once, many have never received any training on sampling for noise exposures. Under- standing the noise sampling process can be critical in accurately evaluating noise exposures and implementing effective controls. Basic Evaluation of Area A common approach to evaluating noise exposures is to walk around the facility with a sound level meter (SLM) and record noise levels as area samples. The readings are sometimes used to produce a “sound map” of the facility showing areas where read- ings were above or below the action level and the permissible exposure limit (PEI), which is the noise exposure OSHA allows able instruments. The main difference in the two meters is the for a workday. In some cases, the readings are used to evaluate accuracy. A Type 1 meter has a listed accuracy of + 1 dBA, while a compliance with the OSHA standard, the need for a hearing con- Type 2 meter has a listed accuracy of + 2 dBA. What do these ac- servation program and the need to implement controls including curacies mean when collecting real-life readings in a workplace? the use of hearing protection. This approach can be acceptable if The reading you record from the SLM, or the noise dosimeter, the readings are representative of the workers’ actual exposures. cannot be taken as 100% accurate. There is a range of sound levels Acceptability of area samples typically depends on the mo- associated with each meter that would contain the true exposure. bility of the workers and the homogeneity of sound levels in the For example, if you recorded a sound pressure level of 90 dBA work areas. When the workers are mobile throughout the work- using a Type 1 SLM, you might think that your exposure was at day, and/or the sound levels change frequently during the work the OSHA PEL. However, because the Type 1 meter has a preci- shift, area readings with an SLM may not be representative of ac- sion of + 1 dBA, the actual level would be between 89 dBA and 91 tual exposures and another evaluation should be used. dBA. The actual level using a Type 2 dosimeter would be between Noise dosimeters are commonly used to measure personal 88 dBA and 92 dBA. With those readings and precision levels exposures to noise in a workplace when mobility is an issue. The you could not be sure if the exposure exceeded the OSHA PEL or noise dosimeter can be worn by the worker and will provide a not. For that reason, the OSHA Technical Manual states that an time-weighted average (TWA) exposure for the worker wearing overexposure using a Type 2 dosimeter would not occur until the the dosimeter. This would include the integration of exposures TWA reading was 92 dBA, meaning the range would be 90 dBA during breaks. Noise dosimeters are typically more costly than to 92 dBA (OSHA, 2013). An exposure then would not exceed the SLMs and can be a disincentive for many companies. action level until it was at least 87 dBA for an 8-hour shift. The noise standard also defines the action level as an exposure of 50% or greater, which can be applied to extended work shifts Meeting the Standards (OSHA, 2008). For example, the action level for a 12-hour shift It’s pertinent to understand the performance characteristic of the would be 82.4 dBA (a 50% exposure). Applying the accuracy of a different types of instruments that can be used for noise expo- Type 2 dosimeter the exposure for a 12-hour shift would have to be sure evaluation. SLMs and dosimeters used for OSHA compli- at least 84.2 dBA to be sure the exposure was above the action level. ance must meet the specifications in American National Stan- dards Institute (ANSI) Standard S1.4 (OSHA, 2013). The ANSI standard sets tolerances for performance and accuracy (OSHA, Noise Apps: Helpful, but Shouldn’t Be the Standard 2013). There are three levels of precision in the ANSI Standard, Smartphones now feature downloadable apps, including safety Types 0, 1 and 2. Type 0 is the most precise and Type 2 is the least and health applications. Many available apps allow a smartphone precise. Type 0 SLMs are used in laboratories so this article will to be used as an SLM or dosimeter, with some even including an not discuss them in relation to field sampling. octave band filter. Some safety and health professionals will use A Type 1 SLM can be used in the field and will provide more an app to collect readings for noise in a facility and base compli- precise noise measurements than most dosimeters. Type 2 SLMs ance on those readings. Care should be taken when using these and noise dosimeters are more common for commercially avail- noise apps in the field. Aree_S/Shutterstock.com 38 Occupational Health & Safety | NOVEMBER/DECEMBER 2023 www.ohsonline.com