dB or Decibel Relationships
<— Quieter ———————— Louder —>
-65dB, -60dB, -23dB, -18dB, -3dB, 0dB
That’s all the audiobook dB specifications.
— Maximum volume is 0dB. Sound gets quieter with negative numbers.
— -3dB is the loudest audiobook peak sound value.
— RMS or loudness needs to hit between -18dB (louder) and -23dB (quieter).
— Noise value has to be quieter than -60dB.
Noise is the troublesome one. Actual submitted performance background noise should be quieter than -65dB in real life. There is no submitting performance noise of -60.2dB, for example. Technically, that does pass, but sooner or later, one of your audiobook chapters is going to fail Noise and you will need to apply noise reduction or some other fix. That fix may make one chapter not match the others and that violates the ACX law that all your chapters match.
https://forum.audacityteam.org/t/measure-between-23db-and-18db-rms/32770/16
It’s possible to use dB for measurements other than the above. You can use them in comparisons. “My voice recording is 3dB louder than yours.”
Sound Pressure Level measures sound volume in free air with special meters. DB SPL uses positive numbers. “My truck engine sound measures 125dB SPL” (threshold of pain). There is no direct relationship between dB (audiobook, above) and dB SPL. Some Phones claim to be able to measure dB SPL directly.
Koz