Illinois Department of Transportation, Ann L. Schneider, Secretary
Patrick J. Quinn, Governor
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Part I Noise Fundamentals

Part II Noise Analysis

Part III Noise Abatement

Frequently Asked Questions

Glossary and Acronyms

Frequently Asked Questions - Noise Fundamentals

At what level will hearing damage occur?
Generally, 120 dBA is recognized as the threshold of pain and considered a dangerous noise level. Noise levels less than 120 dBA can damage hearing if the listener is exposed to the noise for an extended time period. Noise levels less than 90 dBA are generally not recognized as noise levels that can cause hearing damage.

Typically, traffic noise levels in areas of frequent human use do not approach these noise levels. A 90 dBA traffic noise level would occur if a person stood 10 to 20 feet from a roadway carrying approximately 1,000 trucks per hour. It is unlikely that residents would be exposed to this level of noise, and therefore it is unlikely residents experience hearing damage due to traffic noise.

How loud is 67 dBA?
A sound level of 67 dBA is associated with normal speech at 3 feet. Other examples are shown in the "Common Sound Levels" chart within this presentation.

What is Leq?
Leq is the equivalent steady-state sound level which in a specific period of time contains the same acoustic energy as a time-varying sound level during the same period. The Leq is used to describe the period as an overall noise level. The graph below represents the time-varying data for a 50-second monitoring period. For this period, the approximate Leq is 72 dBA.


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