. 2015 Dec 14;20(3):281–289. doi: 10.1055/s-0035-1570072

Table 1. General outlook of the selected articles.

Author / Reference	Recommendation grade Evidence level	Methodology	Evaluated frequencies	Objective	Groups	Outcome
1.Mehrparvar et al¹⁰	Grade B* Level IV*	historical cohort	CA = 250, 500, 1k, 2k, 3k, 4k, 6k and 8k Hz HFA = 10–16kHz	Compare the noise's effects at HFA x CA in employee exposed to occupational noise.	Two groups under the age of fifty. SG = 120 textile workers (108 men and 12 women) with continuous noise exposure of 85+ dBA. CG (106 men and 14 women) not exposed to noise.	In the SG, the hearing threshold was superior in 16000 Hz for both ears, and the difference was statistically meaningful for all frequencies (p < 0.001 for each frequency in each ear); but this comparison did not show a meaningful difference in the control group (p = 0.18, 0.41, 0.72 for the right ear 3000, 4000 and 6000 Hz, and p = 0.39, 0.91, 0.28 for the left ear 3000, 4000, 6000 Hz, respectively). Overall, 54.2% of the cases presented hearing loss in at least one ear and in one frequency at the conventional audiometry. In the high frequencies, the results were of 87.6%. It has been identified a higher incidence of hearing loss in 4000, 6000 and 16000 Hz, given that 16000 Hz the most sensible frequency.
2.Somma et al¹⁸	Grade B* Level IV*	Not explicit	CA = 250 A 8KhZ HFA = 9K A 18KHZ	Investigate the sensibility of HFA x CA at detecting hearing damage due to noise at work.	Two male groups of two cement factories in Italy: SG = 186 CG = 98 To control the age effects in hearing and evaluate better the noise effects over the high frequencies in the groups, they were grouped (21–30; 31–40; 41–50; and 51–60 years old).	HFA can be useful for work evaluation with age inferior to forty years old, after that the age factor can alter the results. In youthful individuals (less than 40 years) the affected frequencies were of 14 and 16kHz.
3.Mehrparvar et al⁵	Grade B* Level IV*	Prospective cross	CA = 500, 1k, 2k, k, 4k, 6k,e 8kHz HFA = 10000, 12000, 14000, and 16000 Hz	Compare three different tests for the premature diagnosis of PAIR (CA, HFA and EOAPD) in workers.	Two groups of 120 men, composed by workers of three ceramic and roof tile companies. SG =exposed to noise levels above 85 dBA; CG = no noise exposure. The average age and work experience were 35.00 ± 6.33 and 10.76 ± 5.52 years and 34.15 ± 5.76 and 11.14 ± 6.12 years in the first and second group, respectively. The differences between both groups regarding the age (p = 0.81) and work experience (p = 0.71) were not significant.	At the present study, the frequencies altered in HFA and in CA were 4000 and 6000 Hz, and 14000 and 16000 Hz. EOAPD in high frequencies (3000, 4000 and 6000 Hz) was more sensitive to noise than CA, and less than HFA, perhaps due to the subjects having a slight hearing loss. Our study did not show a significant difference between both methods for hearing loss detection. It was concluded, with this study, that between the three hearing evaluation methods for workers exposed to noise the HFA is the more useful to a premature diagnosis of PAIR.
4.Korres et al¹⁹	Grade B* Level IV*	Not explicit	CA = 250–8,000 Hz HFA = 9,000–20,000 Hz	Evaluate the hearing of industry workers exposed to occupational noise, using CA and HFA in comparison to a CG	Two groups analyzed for a period of two years, with ages between 24 and 54 years old and from both genders. SG =139 workers (86 males and 53 females) CG =32 workers not exposed to noise with full hearing capacity	HFA shows a better performance in the 12.500–18.000Hz frequency band, but does not show a bigger result variability in comparison to CA. The HFA is a supporting test of CA in the evaluation of the people exposed to occupational noise.
5.Porto et al²⁰	Grade B* Level IV*	Not explicit	CA = 250–8,000 Hz HFA = 9,000–16000 Hz	Investigate the hearing in adult individuals exposed to occupational noise in normal and high frequencies.	Two groups separated by age: 21–30; 31–40; 41–50; 51–60 years old. Regardless of gender. SG = 30 workers exposed to noise CG = 30 workers not exposed to noise	Significant statistical difference between the average value of audibility threshold to right and left ear for both groups (presented in 125000 Hz to CG and 3k for SG). The age factor influences in the enlargement of the auditory threshold.
6.Castro et al²¹	Grade B* Level IV*	Not explicit	CA = 250 a 8khz HFA = 12k	Study the audiometric profile in the frequency of 12 kHz, in workers exposed to occupational noise, comparing the results with a group of individuals not exposed to verify if the frequency of 12 kHz is a premature indicator of the effects of noise exposure.	Two male groups, between 18–49 years old: SG =30 workers in the glass industry with exposure to high levels of noise (from 89.7 dB to 100.7 dB NPS). CG = 30 workers without past exposure to noise.	Workers exposed to occupational noise present a threshold average of 12 kHz significantly worse than not exposed individuals. There was not a significant statistical difference in the frequencies of 250 to 8000 Hz between the groups of exposed and not exposed to noise. There was not a significant statistical difference in the auditory thresholds of both groups regarding the variable age. It was seen an increase in hearing loss regarding the age and the exposure time, even though these results were not statistically significant. The HFA can be an instrument to premature diagnosis of hearing loss if compared with CA, once that only the frequency of 12000 Hz has shown significant statistical differences between the exposed and not exposed groups.

Abbreviations: CA, conventional audiometry; CG, control group; EOAPD,; HFA, high frequency audiometry; SG, study group.