What is the reference pressure for a decibel for music programs like garageband?

Question by Mr. Politics: What is the reference pressure for a decibel for music programs like garageband?

Given that a decibel is a logarithmic unit, if the reference pressure were the smallest that a human ear could hear, I believe (unless I'm mistaken) that would mean if the pressure equaled the reference pressure, 0 decibels would be virtually inaudible. However, in garageband, 0 decibels is clearly very clearly audible. If that is the case, what is the reference pressure used in such programs?




Best answer:

Answer by Tim T
The reference intensity used in defining the decibel (in it's traditional sense) is 10^-12 W/m^2. You're right that 0 decibels should be virtually inaudible. However, the threshold of hearing varies with frequency. For example, at 30 Hz, your threshold of hearing is about 60 dB. But at ~3000 to ~5000 Hz, your threshold of hearing is actually negative dB, as low as maybe -5 dB. Don't know how helpful this is because I'm not familiar with garageband specifically, but I believe that by virtue of using the decibel to measure sound intensity, it is implied that the standard reference intensity is being used.

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