Tools
ACXChecker
Checks a file against Audible's ACX submission spec — RMS, peak level, and noise floor — and gives you a pass/fail report before you submit.
ACX / Audiobook Compliance Checker
Checks each file against Audible’s ACX submission spec: RMS between −23 and −18 dB, peak level at or below −3 dB, and noise floor at or below −60 dB.
Everything runs in your browser — files never leave your computer.