ACX check question

Hello Again Koz and Steve,

I have downloaded the ACX check which I use on my Librivox recordings (not required - but I like to play). I noticed something confusing about it: I record say a 2 minute passage and for novelty I do the ACX check and it says - passed ACX check. Cool! If I highlight a 10 sec piece in the same passage and for curiosity do the check it says: failed due to noise floor bad juju. BTW, I do the AMP 0.0/ Steve’s EQ thing/LIMITER limit -6, hold 10, soft limit/REPLAYGAIN. Is the ACX check an average of the whole or am I going to have to take another nap?

I have not done ACX - but maybe.


You need to know ACX Check noise analysis depends on finding at least half-second of Room Tone to analyze. If it doesn’t find that, the reading will go straight into the toilet.

That may seem a little wacky, but if you read the ACX Submission Specifications, some Room Tone is built in and they will reject a submission without it.

ACX Check is not a generic analysis tool although you can use it like that if you’re careful.

It is a collection developed from other tools and techniques. You don’t have to use ACX-Check. I published a page of analysis techniques which will do the same thing—at great expense of time. Get a good strong cup of coffee/tea and comfortable chair…


There are several new tools available that also abbreviate preparing an ACX submission from your work. Until those tools, there was no way to intentionally set RMS, one of the ACX specifications. You always had to do it sideways around the barn with other tools. Steve developed ACX Normalize which does that in one step. Boom.

No more compressor. If you did a credible job announcing, simple Limiter will get you 99% of the way home with very little sound damage.


Either last year or the year before, I published an April First software package which would magically turn whatever you shot in whatever condition into a broadcast-ready submission. Complete fabrication, but it turns out we can actually do many of those jobs now which were a fever dream when I wrote that April Fool story.

Under development.


Thanks Koz,

So the reason the snippets of audio don’t read OK in ACX test is because there isn’t sufficient room noise but the longer version has the sufficient room noise to test and it passes muster. Awesome!

Thank you

Before you get all excited about submitting to ACX, ACX Check is only the first layer of submission testing. It’s the most difficult for new users because of the hardware requirements. No, you probably can’t buy a Yeti and start publishing books.

If you did pass ACX-Check but you got there by beating your voice with a stick (heavy compression, severe or multiple noise reductions, gating…) then the performance is going to fail for Excessive Processing. The work is supposed to sound like natural conversation (I call it listening fascinated over cups of tea while somebody tells you a juicy story).

It is not supposed to sound like a bad cellphone call. Some of the voice corrections recommended were specifically chosen because ACX can’t find them.


Somebody recently posted with a podcast produced with hard gating, we assume to cover up a noisy microphone in a bad room. What that does is dump blackness of space silence between each word as you speak.



Help!! I’m new to the audio world and am trying to figure out how to verify that I am meeting ACX standards. I see in your post you note a new plug in. What is/are the plug-ins? Lots of silly questions but with the communities help I’ll be a lot smarter down the road.

Thanks in advance!!

You’ll find acx-check on this wiki page:

You should also read carefully the general plugin installation instructons:

Thanks for the response. Now next silly question. Per the directions I’m to save the file in the Audacity Plug-in folder. However when I do this I receive an error message that I don’t have access? Any ideas?

Any ideas?

You need better access!

We need to wait for a heavy Windows elf which I’m not.