Further work involves validating the approach and parameters in occupational settings, and adapting this method to other types of HPDs such as earmuffs or dual hearing protection.
Laboratory results collected on human test-subjects suggest that the proposed method is not only valid for a wide variety of self-generated sounds, it is efficient regardless of the amount of attenuation provided by the earplug. A comparison of the two microphones signals, through coherence calculations, provides sufficient information as to whether the protected noise levels originate mainly from the wearer or from external noise sources. The method uses a dual-microphone earpiece able to take measurements both under the earplug and outside the ear.
This paper presents a low computational method to perform in-ear noise dosimetry under an earplug while excluding the noise contributions from the wearer. However, these systems can be affected by the noise events induced by the wearer, though research has shown that the risk of hearing loss inherent to self-generated sounds (voice, swallowing, chewing) can be less than for external noise. To overcome the difficulties in assessing the attenuation provided by HPDs, continuous monitoring systems of an individual’s noise exposure under the HPD show promise. While personal noise exposure assessments are necessary to prevent noise-induced hearing loss in the workplace, standard personal noise dosimeters are limited when measuring the noise exposure of individuals wearing hearing protection devices (HPD). Due to a low number of data points, no statistically significant results were obtained without reasonable doubt, but several categories approached significance further investigation of these phenomena is recommended. The impact of rooms’ sound absorption and sound scattering properties on those kurtosis levels is presented and supported with statistical analysis. This study calculated room impulse response-based metrics of rooms’ acoustical properties and the kurtosis levels (a metric which has been proposed and vetted during the last two decades) for three different noise signals. Much work has been done on establishing metrics that accurately assess the severity and hearing risk associated with impulsive noise, but the effects of room acoustic conditions on those metrics have been heretofore understudied. While many regulations and guidelines for noise exposure exist, their mathematical basis is stronger for continuous noise, and concerns have been raised about the possibility that impulsive noise may be more harmful to people’s hearing than those metrics would let on. Impulsive noise can be common in certain occupational and recreational settings, such as manufacturing plants, construction sites, and firing ranges. The Berger et al "Noise Navigator" database shows this egregious difference in peak levels for such sources as the continuous operation of a motorboat engine and revolver shots (2015) a study by Kamerer et al (2019) uses those particular data to make the extended argument that impulsive noise exposure can be much more deleterious than many conventional sound measurement metrics might indicate, using a weighting system designed by that study's authors. This issue has been reaffirmed several times, as in Kardous and Willson (2004), whose research informed recommended improvements to dosimeters such that they could recognize the severity of an impulsive noise environment (Kardous, Willson, and Murphy 2005) meanwhile, it was seemingly ignored by a set of DRC proposed in the early stages of research into impulsive noise (Ward 1968).
For example, one of the first and most persistent problems observed by the body of work is that the peak sound pressure levels of impulsive noise can frequently exceed the limits of applicability stated in standards, damage risk criteria (DRC), and most flagrantly the physical limitations of sound measurement equipment prescribed in such documents.
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