USSI | An Acoustical and Industrial Building Podcast
06 Part 2 Acoustical Rules of thumb and Demystifying the Decibel
Dec 3, 2019 · 10 min
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When comparing decibel values, that best way to think about it is to consider how decibel values combine. For example, the combination of a sound having a level of 50 dB, and a second sound having an equal sound level of 50 dB is 53 dB. In shorthand (but not arithmetically correct) 50 dB, quote-unquote, plus 50 dB is 53 dB. This gives us a good rule of thumb to live by:

Two equal sound levels combine to be 3 decibels greater than the individual. 65 dB "+" 65 dB = 68 dB

When two sound levels differ by 10 decibels or more, when combined, the lesser level can be ignored. 65 dB + 75 dB = 75 dB

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