ACX Audiobook Testing

You can do ACX AudioBook acceptance testing with normal, internal Audacity tools. This will only test against technical standards, not theatrical.

Manual tools can be handy if the automated Audacity conformance tool ACX Check fails or gives irrational answers.


— You should do these tests on a simple 10 second sound file before you read long works.

— The bracket values are ACX AudioBook standards.

— Effect > Amplify will not give a negative number. That's OK. The number itself is valid.


— Measure Noise [-60dB or quieter]

Drag-Select room tone or a pure, quiet background portion of your file.

Analyze > Contrast > Foreground > Measure Selection > Leave Contrast open.

— Measure RMS (loudness). [Between -18dB (louder) and -23dB (quieter)]

Select the whole clip by clicking Select on the left.

Background > Measure Selection.

Those two numbers, foreground and background are your ACX NOISE and ACX RMS values. > Close

— Measure Peak Sound. [-3.0dB or quieter]

Select the whole clip with the Select button on the left.

Effect > Amplify > Read the top number—Amplification—and CANCEL. Do Not Apply the Tool!!

Edit > UNDO if you apply it by accident and the blue waves change size.

— Help

You can ask questions on the Audacity Help Forum.

The forum is moderated. Someone will look at your question before it becomes visible. Don't double post.

dB or decibel values explained.

ACX audiobook standards explained.