The following table shows decibel (dB) reduction levels and corresponding reduction in sound pressure levels (SPL).

    What is a decibel? A decibel (dB) is a unit of measurement that gauges the intensity of sound. The units define how loud a noise source is, ranging on a comparative scale from 0 decibels to 194 decibels -- a decibel or dB reading of “0” indicates the faintest sound the human ear can detect, while a dB reading of “180” would be the equivalent to standing on a rocket pad during launch.


    Your average day is filled with sounds that typically range from 30-100 dB. Daytime hours average 10 dB more sound pressure than night time hours. Conversational voice levels average a 65 dB rating, while OSHA demands hearing protection for factory workers exposed over an 8 hour period to levels stronger than 85 dB. The pain threshold for human ear starts at about 120 dB.


    The decibel scale is logarithmic, not linear. This simply means that for every 3 decibels you move up or down the scale from 0-194, you are adding or dropping 50% of your remaining sound pressure levels to your exposure. By dropping 6 decibels, for instance, you first move 3 dB, and then another 3 dB. For each 3 dB you drop, your sound pressure levels will drop another 50% of the remaining sound pressure. The following table will help illustrate the order of magnitude associated with dB.


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