Definition - What does Dose mean?
Dose, with regard to workplace hearing conversation, refers to a measurement used to calculate the amount of noise a worker is exposed to over a specified period of time.
The noise dose for a worker is calculated using both the noise level in the employee's work environment and the duration of his or her exposure. This is because a person's hearing may be damaged by either a brief exposure to a very loud noise, or a longer exposure to noise at a lower decibel level. For instance, it may take two hours of exposure for hearing damage to occur at 91 decibels, but only 15 minutes of exposure at 100 decibels.
A worker's dose is expressed as a percentage of the permissible eight hour time-weighted-average exposure (TWA). For example, an 8-hour exposure to 90 decibels is considered a 100% dose. If the worker were exposed to 90 decibels for only four hours, the dose would be 50%.
Because sound levels usually vary of the course of a work day, several individual calculations may need to be combined to determine the individual's dose.
WorkplaceTesting explains Dose
The U.S. Occupational Safety and Health Administration defines this noise dose and provides instructions for its calculation in the Appendicies to 29 CFR 1910.95.
To accurately assess the dose for a work area, the permissible exposure limit or criterion level must be determined. Additionally, of the decibel level varies by more than a specified amount during an 8-hour work day, further adjustments must be made to the calculation. The variance that triggers this alteration of the noise dose is referred to as the exchange rate and is usually set at either 5 or 3 decibels.
A noise monitoring device called a dosimeter is often used to determine what a specific worker's dose or exposure to sound is over the course of a work day. This device is usually worn by the employee to record his or her personal sound exposure.