How do you determine the combined effect of multiple noise sources?

The combined effect of multiple noise sources is determined using logarithmic addition rules because sound levels typically measure sound intensity in decibels (dB), a logarithmic scale. Noise levels do not simply add arithmetically because each increase of 10 dB represents a tenfold increase in intensity.

When combining sound sources, the proper method involves converting the decibel levels to their corresponding intensities (which are linear values), summing those intensities, and then converting the total back to a decibel level. This method accounts for how sound interacts in real-world environments, providing an accurate representation of overall noise exposure.

In practice, this means that if you have multiple sources of noise, instead of just summing their dB levels directly, you would apply the logarithmic formula to correctly assess the combined effect on a person's hearing safety or comfort. This process speaks directly to the precautions and assessments required in industrial hygiene regarding noise exposure and the risk of hearing loss.