Two speakers are not twice as loud. Decibels add logarithmically, and sound spreads with the inverse-square law — see how loudness really combines and fades.
Sound Levels (dB SPL)Live
adding & spreading loudness
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Decibels are logarithmic, so loudness does not add the way you expect: two identical sources are only 3 dB louder than one, and ten are 10 dB. Meanwhile a point source drops 6 dB every time the distance doubles (the inverse-square law). Sustained exposure above 85 dB risks hearing damage.
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How it works
Because decibels are logarithmic, doubling the number of equal sources adds only 3 dB and tenfold adds 10 dB. A point source loses 6 dB every time you double the distance, the inverse-square law. Sustained exposure above 85 dB risks hearing damage — the dashed line here marks that threshold.
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