ACX Audiobook Checker Online
Review an audiobook file’s RMS level, peaks, sample rate, and MP3 encoding. Select a room-tone section to measure the background noise separately.
READY TO ANALYZE
Drop your audio here
Up to 50 MB · 5 minutes · Mono or stereoYour measurements will appear here
Choose your audio and start the check.
Which ACX audio requirements are checked?
The report compares RMS with -23 to -18 dB, sample peak with a -3 dB ceiling, selected room tone with -60 dB RMS, and encoding with 44.1 kHz MP3 at 192 kbps or higher constant bitrate. Unmeasured criteria remain separate from passing results.
Choose real room tone
Select a section with no narration or music, then confirm the selection. Digital silence does not show the microphone’s noise floor. Listen separately for mouth sounds, plosives, edits, pronunciation, and chapter consistency; a numerical report does not cover those editorial checks.
Questions about this tool
Which ACX audio requirements are checked?
The report compares RMS with -23 to -18 dB, sample peak with a -3 dB ceiling, selected room tone with -60 dB RMS, and encoding with 44.1 kHz MP3 at 192 kbps or higher constant bitrate. Unmeasured criteria remain separate from passing results.
Can I download the result?
Yes. Analysis tools provide a report you can save. Audio Normalizer and Volume Booster also create a WAV you can play and download. Keep the page open until your result has arrived.
Which files can I check?
Upload mono or stereo WAV, MP3, M4A, AAC, FLAC, OGG, OPUS, or WebM audio, up to 50 MB and five minutes. The measured file keeps its original channels.