Introduction Annual audiometric screening is the default protocol for occupational settings. This frequency of testing is costly for the health system, employees and employers in terms of money, resources and time.

Objectives To investigate the annual rate of clinical deterioration of hearing of workers. Secondly, the study aimed to establish an effective, efficient, hearing screening frequency protocol for noise induced hearing loss (NIHL) screening in noise exposed workers in Israel.

Methods A historical cohort study was conducted. Audiometric surveillance data from the Jerusalem occupational medicine registry of employees in various industries across the district from 2006–2017 were used. Plants from Jerusalem district with noise levels, equal to or greater than a time-weighted average (TWA) sound level of 85dB(A) for 8-hour work day were considered hazardous. Joinpoint regression was used to assess significant changes in the trend of detected hearing loss for different time intervals between audiological check-ups.

Results 263 noise exposed workers and 93 reference workers were followed for 12 years producing 1913 audiograms for analyses. Threshold shifts among noise-exposed workers became significantly stable at approximately 1dB/year at three years (p=0.037) using frequencies 1–4 kHz. Noise- exposed workers, aged below 50 at entry, showed stabilized threshold shifts of 0.8dB annually on intervals of 3–8 years, compared to 0.35dB shift annually using the 0.5–2 kHz.

Conclusions The trend of mean hearing threshold shifts in noise-exposed workers becomes a nearly constant at 0.8dB shift annually at 3 years onwards. These small annual changes are within the measurement error of audiometers (±5 dB). Therefore, intervals between subsequent tests should be considered so as to identify a significant and real deterioration in hearing and avoid unnecessary medical investigations. A triennial audiometric screening frequency would be a better surveillance method for noise exposed workers in the category of 85–90dB(A) without other known risk factors.