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City Risk LogoLoss Prevention

Risk Management, Portland, OR

Action Level:  When there is a noise level exposure to an 8-hour time-weighted average of 85 decibels or a dose of 50 percent.

Administrative Controls:  A method of limiting daily noise exposure by control of the work schedule.

Affected Employee:  An employee subject to a noise exposure equal to, or exceeding the Action Level and included in the Hearing Conservation Program.

Attenuators:  Means any hearing protective device or material, which is capable of being worn on the head, covering the ear canal or inserted in the ear canal; is designed wholly or in part to reduce the level of sound entering the ear; and has a scientifically accepted indicator of its noise reduction value.

Baseline Audiogram:  Means the audiogram against which future audiograms are compared to determine the extent of change of hearing level.

Clinical Audiological Evaluation:  A clinical evaluation of a person's hearing capability, using a calibrated pure-tone audiometer and performed in accordance with 29 CFR 1910.95 (g) and (h). At SLAC, such tests are provided on site by the Medical Department.

Decibel (dB):  Means a unit of measurement of sound pressure levels.

dB(A):  Means the sound pressure level in decibels measured on the A-weighted scale.

Dose:   The dose is represented as a percentage of allowable noise a worker can be exposed to during one day. It is based on OSHA’s maximum Permissible Exposure Level (PEL) of 90 dBA over an 8 hour work day, which is equal to a 100% dose. If the total dose results in 50% or higher, they must be included in your HCP as they are at risk to noise induced hearing loss.

Engineering Controls:  Means any procedure or method, other than an administrative control or personal hearing protection that reduces the sound level either at the noise source or in the hearing zone of the exposed personnel.

Hearing Conservation Program Services Contract;  Means a competitively bid contract with an outside contracted vendor to provide services necessary to identify noise hazards, measure employee exposures and provide audiometric testing to City bureaus.


High Noise equipment, machinery or work areas:  Identified by OSHA approved noise-sampling methods that record levels at the 85 dBA action levels or above.

Noise Dosimeter Sampling:  Is worn by the individual during the day, measures the sound near the entrance to the ear, and measures the amount of noise encountered continuously as the individual goes about the day’s work.


Noise Hazard:  For the purposes of the Hearing Conservation Program, is defined as "any sound that can cause hearing loss, tinnitus, or other damage to the ear" that is above the action level defined in statute.

Noise Reduction Rating (NRR):  Measure of the estimated attenuation capacity of a hearing protector to represent the approximate noise reduction, in dBA.

Other Employees:  All employees other than those designated as Affected Employees and not included in the Hearing Conservation Program.

Sound Level Meter:  A hand-held, direct-reading instrument with a microphone, an electronic-filter network, and a visual display such as a meter or digital readout. Because sound-level meters provide a real-time indication of noise intensity, they are typically used to survey an area.

Significant Standard Threshold Shift:  A negative change in hearing threshold relative to the baseline audiogram of an average of 25 dB or greater in either or both ears averaged over 2000, 3000, 4000 Hz.  This confirmed shift must be recorded on the OSHA 300 Log.

Standard Threshold Shift (STS):   A negative change in hearing threshold relative to the baseline audiogram of an average of 10 dB or more at 2000, 3000, and 4000 Hz in either ear.

Standard Threshold Shift Revised Baseline:  Occurs when the same level of loss (STS) of hearing is present and consistent over two hearing test cycles and an audiologist verifies the change is consistent. This new documented level of hearing can be used for future comparisons to determine if the employee is having further hearing loss or if there are improvements to an employees hearing capabilities.

Time Weighted Average (TWA): That sound level, which if constant over an 8-hour exposure, would result in the same noise dose as is measured.