At what decibel level does OSHA's standard threshold shift (STS) start for frequencies of 2k, 3k, and 4k?

The standard threshold shift (STS) as defined by OSHA reflects a measurable change in a worker's hearing ability due to exposure to noise. For the frequencies of 2k, 3k, and 4k Hz, the STS is recognized when there is a shift in hearing levels of 10 dB or more from the baseline audiogram. This threshold is established to help identify the early signs of hearing loss in workers who are exposed to noise, thus facilitating preventive measures to protect their hearing.

Establishing the STS at 10 dB serves as a critical marker in occupational health, enabling organizations to implement hearing conservation programs and develop strategies to mitigate further risk of hearing impairment. By monitoring the hearing of employees with this standard, industrial hygienists can ensure that effective controls are put in place whenever significant shifts are detected.