# Psychophysics: Decibels

• Medical

## Main Question or Discussion Point

Decibels are the measuring unit for sound energy. The absolute threshold for hearing is arbitrarily defined as zero decibels. Every 10 decibels correspond to a ten-fold increase in sound. Thus, normal conversation (60 dB) is 10,000 time louder than a 20 dB whisper.
I don't understand the math of the 10 fold system.
Could someone go into detail of it for me?

I just don't see how that works.

10 db = 100
20 = 1000
30 = 10000?

i don't understand the system here.

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It's a log scale

$$I(db) = 10*log_{10}(\frac{I}{I_0})$$

For example

$$10db = 10*log_{10}(10)$$

$$30db = 10*log_{10}(1000)$$

$$60db = 10*log_{10}(1000000)$$

I don't understand that log stuff or I think I'd have this understood by now.

==update==
Ah, I understand it a bit better now after doing some math work. Thank you.

simply the 6 part of 60 could signify 6 zeros after the 1, making it 1 million.

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