tonistry.

Specs & measurements

Decibel (dB)

Also called dB, dB SPL

The decibel is the logarithmic unit audio uses for level and ratio. Each 10 dB is a tenfold change in power and sounds roughly twice as loud; about 1 dB is the smallest change most people notice. Almost every audio specification is written in it.

120100806040200dB SPLpainloud concertconversationthreshold of hearingpower×1 trillion×10 billion×100 million×1 million×10,000×100×1+10 dB10× the power≈ twice as loud
On the dB SPL scale 0 dB is the threshold of hearing, conversation is about 60 dB and a loud concert 110 dB. Each 10 dB step is ten times the power and sounds roughly twice as loud, so the 120 dB span to pain is a trillionfold change in power.

Because hearing works on ratios, a linear scale would be useless: the span from the quietest audible sound to pain is a factor of a trillion in power, or 120 dB. Sound pressure level, written dB SPL, puts 0 dB at the threshold of hearing; normal conversation is about 60 dB and a loud concert 110 dB.

Specifications use decibels for ratios too: SNR, SINAD, Crosstalk and Sensitivity are all differences in dB. A tonal change of 1 dB over a broad band is about the smallest most people notice; a 3 dB bass shelf is obvious.

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