The evaluation of noise effects on the standard threshold of hearing can be complicated. Although studies have been conducted to determine the effects of noise on the hearing, they have also failed to show that there is any relationship between exposure and noise level. In addition to the auditory effect, noise can also have nonauditory consequences such as psychological stress, job performance disruption, and hypertension. Some researchers believe that noise can even contribute to industrial accidents.
In addition to the subjective effects of noise exposure, the objective of the assessment is to identify specific noise levels. This type of evaluation has a good sensitivity and specificity, and the results correlate with the pure-tone average of frequencies. In addition, it has a good test validity due to its moderate intraclass correlation coefficient. However, one should consider that this is not a simple method to detect the impact of noise on the standard threshold of hearing.
For the Lee-Feldstein study, the noise exposure was between 85-114 dB. The control subjects were exposed to similar noise levels. The results showed that the difference between the groups was not significant. The results were not significant in four of the five factories studied. Therefore, this method does not provide conclusive results about noise exposure. There are still some important aspects to consider, however. A high level of sensitivity is crucial in noise-related studies.
The CHABA criteria were not validated, but the findings were generally consistent. The results of the study showed that there was a direct relationship between the threshold shift and cochlear damage. For example, the CHABA criteria assumed regular bursts of noise with quiet periods to allow for hearing recovery. This is not the typical industrial noise environment. In a workplace, workers always develop a temporary threshold shift before developing a permanent shift. Consequently, the temporary threshold shift is an important metric in assessing the effects of noise on a worker’s hearing.
In addition to assessing the impact of noise on hearing, the ANSI S1.1-1994 standard describes the sound level in a workshop. This is a standard reference for occupational exposure levels in noisy workplaces. It also specifies the noise level that is considered safe. The ANSI S1.1-1994 standard defines the threshold level in decibels, which is the amount of sound energy that causes harm. Hence, the ANSI S1.1-1994 reference is considered the standard for measuring the sound exposure in a worksite.
The study was conducted on 228 workers in a Canadian smelter. The daily noise exposure was mostly below the 90 dB standard in Canada. No hearing protection was required at that time. The prevalence of hearing loss in the exposed workers was found to be between 14 and 32 percent, while the number of controls was four percent. Moreover, the highest sound pressure balance was related to a cutting-wood workshop.