Representing all decibel values as positive

Is it possible to see decibel values that start at 0 dB so that the values are all positive? Yes, you just need to decide what you want to use as your 0 dB reference amplitude. In digital audio, an amplitude of 1 is used as the 0 dB reference. In measuring real-world sound, the human threshold of hearing at 1 KHz (something like .0002 microbar) is usually used as the 0 dB reference value. Here’s an example using (roughly) the smallest obtainable nonzero amplitude in a 16-bit signal as the reference value, yielding a scale from about 0 to 90 dB.