Why is it zero if you hear something?
In: Technology
So that is multifaceted question, but the simplest explanation to your question I think would be that 0dB while looking at a calibrated meter is a reference point. In a digital full scale meter for recording, going above zero would induce signal clipping.
dB is a ratio so 0 is the base reference. +dB is an increase and -dB is a decrease. 0 is chosen and then adjustments are made from there.
dB is telling you how much louder to make something.
0 dB means dont make it any louder. Negative dB means make it quieter.
In digital audio, 0 db usually means full scale audio. it should be listed as 0 dbfs. Decibels are a ratio between a reference level and a value. The full scale reference is the maximum possible level without clipping and distortion. That’s why it is so important. Normal levels are all negative values.
In analog, it is a certain power or voltage. Pro analog audio uses +4 dbm (0 dbm=1 milliwatt. Consumer audio uses -10 dbV.
dB is a logarithmic scale. Every time you add 10 dB, you make the sound ten times as loud. Every time you subtract 10 dB, you make the sound one tenth as loud. Zero dB is like multiplying the sound by 1: it’s just the original, unchanged sound, at it’s original volume.
0 dB means the measured power/voltage/amplitide/loudness is exactly equal to whatever reference it refers to.
Because Bel scale is the logarithmic of power ratio. Hence
dB = 10 log(P/P)
Where the above P is the power of the measured, and the below P is the reference
Because log(1) = 0, when the measured result is equal to reference, the dB is 0
In sound measurement, 0 dB literally means 0 dB SPL or deciBel Sound Pressure Level. dB SPL means the reference is the SPL of the threshold of hearing (20 microPascal). 0 dB means the level is equal to the threshold of hearing.
In digital mixer or any form of digital audio, the Golden rule is that you cannot go above the given highest amplitude because the system will not allow. So the unit used is called dB FS or deciBel Full Scale, referencing the highest grid available for amplitide (equivalence to voltage or SPL). Therefore, the top value is 0 dB
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